Ultrafast phase and amplitude pulse shaping with a single, one-dimensional, high-resolution phase ma

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超快光学第19章放大(教育研究)

Pulse energy vs. Repetition rate
Pulse energy (J)
100
10-3
Regen + multimulti-pass 10-6
10-9
10-3
100
Regen + multipass
Regen
1 W average power
RegA
Cavity-dumped oscillator
In both cases, pump pulse energy is wasted, and amplification is poor.
章节课堂
11
So we need many passes.
All ultrashort-pulse amplifiers are multi-pass.
pump
its orthogonal state.
Abruptly switching a Pockels cell allows us to extract a pulse from
a cavity. This allows us to achieve ~100 times the pulse energy at
This is the opposite of Q-switching: it involves switching from
minimum to maximum loss, and 章it节’s课c堂alled “Cavity Dumping.”
5
Cavity dumping: the Pockels cell
Intermediate case interpolates
between the two:

光电技术专业英语词汇

《光电技术》专业英语词汇1.Absorption coefficient 吸收系数2.Acceptance angle 接收角3.fibers 光纤4.Acceptors in semiconductors 半导体接收器5.Acousto-optic modulator 声光调制6.Bragg diffraction 布拉格衍射7.Air disk 艾里斑8.angular radius 角半径9.Airy rings 艾里环10.anisotropy 各向异性11.optical 光学的12.refractive index 各向异性13.Antireflection coating 抗反膜14.Argon-ion laser 氩离子激光器15.Attenuation coefficient 衰减系数16.Avalanche 雪崩17.breakdown voltage 击穿电压18.multiplication factor 倍增因子19.noise 燥声20.Avalanche photodiode(APD) 雪崩二极管21.absorption region in APD APD 吸收区域22.characteristics-table 特性表格23.guard ring 保护环24.internal gain 内增益25.noise 噪声26.photogeneration 光子再生27.primary photocurrent 起始光电流28.principle 原理29.responsivity of InGaAs InGaAs 响应度30.separate absorption and multiplication(SAM) 分离吸收和倍增31.separate absorption grading and multiplication(SAGM) 分离吸收等级和倍增32.silicon 硅33.Average irradiance 平均照度34.Bandgap 带隙35.energy gap 能级带隙36.bandgap diagram 带隙图37.Bandwidth 带宽38.Beam 光束39.Beam splitter cube 立方分束器40.Biaxial crystal双s 轴晶体41.Birefringent 双折射42.Bit rate 位率43.Black body radiation law 黑体辐射法则44.Bloch wave in a crystal 晶体中布洛赫波45.Boundary conditions 边界条件46.Bragg angle 布拉格角度47.Bragg diffraction condition 布拉格衍射条件48.Bragg wavelength 布拉格波长49.Brewster angle 布鲁斯特角50.Brewster window 布鲁斯特窗51.Calcite 霰石52.Carrier confinement 载流子限制53.Centrosymmetric crystals 中心对称晶体54.Chirping 啁啾55.Cladding 覆层56.Coefficient of index grating 指数光栅系数57.Coherence连贯性pensation doping 掺杂补偿59.Conduction band 导带60.Conductivity 导电性61.Confining layers 限制层62.Conjugate image 共轭像63.Cut-off wavelength 截止波长64.Degenerate semiconductor 简并半导体65.Density of states 态密度66.Depletion layer 耗尽层67.Detectivity 探测率68.Dielectric mirrors 介电质镜像69.Diffraction 衍射70.Diffraction g rating 衍射光栅71.Diffraction grating equation 衍射光栅等式72.Diffusion current 扩散电流73.Diffusion flux 扩散流量74.Diffusion Length 扩散长度75.Diode equation 二极管公式76.Diode ideality factor 二极管理想因子77.Direct recombinatio直n接复合78.Dispersion散射79.Dispersive medium 散射介质80.Distributed Bragg reflector 分布布拉格反射器81.Donors in semiconductors 施主离子82.Doppler broadened linewidth 多普勒扩展线宽83.Doppler effect 多普勒效应84.Doppler shift 多普勒位移85.Doppler-heterostructure 多普勒同质结构86.Drift mobility 漂移迁移率87.Drift Velocity 漂移速度88.Effective d ensity o f s tates 有效态密度89.Effective mass 有效质量90.Efficiency 效率91.Einstein coefficients 爱因斯坦系数92.Electrical bandwidth of fibers 光纤电子带宽93.Electromagnetic wave 电磁波94.Electron affinity 电子亲和势95.Electron potential energy in a crystal 晶体电子阱能量96.Electro-optic effects 光电子效应97.Energy band 能量带宽98.Energy band diagram 能量带宽图99.Energy level 能级100.E pitaxial growth 外延生长101.E rbium doped fiber amplifier 掺饵光纤放大器102.Excess carrier distribution 过剩载流子扩散103.External photocurrent 外部光电流104.Extrinsic semiconductors 本征半导体105.Fabry-Perot laser amplifier 法布里-珀罗激光放大器106.Fabry-Perot optical resonator 法布里-珀罗光谐振器107.Faraday effect 法拉第效应108.Fermi-Dirac function 费米狄拉克结109.Fermi energy 费米能级110.Fill factor 填充因子111.Free spectral range 自由谱范围112.Fresnel’s equations 菲涅耳方程113.Fresnel’s optical indicatrix 菲涅耳椭圆球114.Full width at half maximum 半峰宽115.Full width at half power 半功率带宽116.Gaussian beam 高斯光束117.Gaussian dispersion 高斯散射118.Gaussian pulse 高斯脉冲119.Glass perform 玻璃预制棒120.Goos Haenchen phase shift Goos Haenchen 相位移121.Graded index rod lens 梯度折射率棒透镜122.Group delay 群延迟123.Group velocity 群参数124.Half-wave plate retarder 半波延迟器125.Helium-Neon laser 氦氖激光器126.Heterojunction 异质结127.Heterostructure 异质结构128.Hole 空穴129.Hologram 全息图130.Holography 全息照相131.Homojunction 同质结132.Huygens-Fresnel principle 惠更斯-菲涅耳原理133.Impact-ionization 碰撞电离134.Index matching 指数匹配135.Injection 注射136.Instantaneous irradiance 自发辐射137.Integrated optics 集成光路138.Intensity of light 光强139.Intersymbol interference 符号间干扰140.Intrinsic concentration 本征浓度141.Intrinsic semiconductors 本征半导体142.Irradiance 辐射SER 激光144.active medium 活动介质145.active region 活动区域146.amplifiers 放大器147.cleaved-coupled-cavity 解理耦合腔148.distributed Bragg reflection 分布布拉格反射149.distributed feedback 分布反馈150.efficiency of the He-Ne 氦氖效率151.multiple quantum well 多量子阱152.oscillation condition 振荡条件ser diode 激光二极管sing emission 激光发射155.LED 发光二极管156.Lineshape function 线形结157.Linewidth 线宽158.Lithium niobate 铌酸锂159.Load line 负载线160.Loss c oefficient 损耗系数161.Mazh-Zehnder modulator Mazh-Zehnder 型调制器162.Macrobending loss 宏弯损耗163.Magneto-optic effects 磁光效应164.Magneto-optic isolator 磁光隔离165.Magneto-optic modulator 磁光调制166.Majority carriers 多数载流子167.Matrix emitter 矩阵发射168.Maximum acceptance angle 最优接收角169.Maxwell’s wave equation 麦克斯维方程170.Microbending loss 微弯损耗171.Microlaser 微型激光172.Minority carriers 少数载流子173.Modulated directional coupler 调制定向偶合器174.Modulation of light 光调制175.Monochromatic wave 单色光176.Multiplication region 倍增区177.Negative absolute temperature 负温度系数 round-trip optical gain 环路净光增益179.Noise 噪声180.Noncentrosymmetric crystals 非中心对称晶体181.Nondegenerate semiconductors 非简并半异体182.Non-linear optic 非线性光学183.Non-thermal equilibrium 非热平衡184.Normalized frequency 归一化频率185.Normalized index difference 归一化指数差异186.Normalized propagation constant 归一化传播常数187.Normalized thickness 归一化厚度188.Numerical aperture 孔径189.Optic axis 光轴190.Optical activity 光活性191.Optical anisotropy 光各向异性192.Optical bandwidth 光带宽193.Optical cavity 光腔194.Optical divergence 光发散195.Optic fibers 光纤196.Optical fiber amplifier 光纤放大器197.Optical field 光场198.Optical gain 光增益199.Optical indicatrix 光随圆球200.Optical isolater 光隔离器201.Optical Laser amplifiers 激光放大器202.Optical modulators 光调制器203.Optical pumping 光泵浦204.Opticalresonator 光谐振器205.Optical tunneling光学通道206.Optical isotropic 光学各向同性的207.Outside vapor deposition 管外气相淀积208.Penetration depth 渗透深度209.Phase change 相位改变210.Phase condition in lasers 激光相条件211.Phase matching 相位匹配212.Phase matching angle 相位匹配角213.Phase mismatch 相位失配214.Phase modulation 相位调制215.Phase modulator 相位调制器216.Phase of a wave 波相217.Phase velocity 相速218.Phonon 光子219.Photoconductive detector 光导探测器220.Photoconductive gain 光导增益221.Photoconductivity 光导性222.Photocurrent 光电流223.Photodetector 光探测器224.Photodiode 光电二极管225.Photoelastic effect 光弹效应226.Photogeneration 光子再生227.Photon amplification 光子放大228.Photon confinement 光子限制229.Photortansistor 光电三极管230.Photovoltaic devices 光伏器件231.Piezoelectric effect 压电效应232.Planck’s radiation distribution law 普朗克辐射法则233.Pockels cell modulator 普克尔斯调制器234.Pockel coefficients 普克尔斯系数235.Pockels phase modulator 普克尔斯相位调制器236.Polarization 极化237.Polarization transmission matrix 极化传输矩阵238.Population inversion 粒子数反转239.Poynting vector 能流密度向量240.Preform 预制棒241.Propagation constant 传播常数242.Pumping 泵浦243.Pyroelectric detectors 热释电探测器244.Quantum e fficiency 量子效应245.Quantum noise 量子噪声246.Quantum well 量子阱247.Quarter-wave plate retarder 四分之一波长延迟248.Radiant sensitivity 辐射敏感性249.Ramo’s theorem 拉莫定理250.Rate equations 速率方程251.Rayleigh criterion 瑞利条件252.Rayleigh scattering limit 瑞利散射极限253.Real image 实像254.Recombination 复合255.Recombination lifetime 复合寿命256.Reflectance 反射257.Reflection 反射258.Refracted light 折射光259.Refractive index 折射系数260.Resolving power 分辩力261.Response time 响应时间262.Return-to-zero data rate 归零码263.Rise time 上升时间264.Saturation drift velocity 饱和漂移速度265.Scattering 散射266.Second harmonic generation 二阶谐波267.Self-phase modulation 自相位调制268.Sellmeier dispersion equation 色列米尔波散方程式269.Shockley equation 肖克利公式270.Shot noise 肖特基噪声271.Signal to noise ratio 信噪比272.Single frequency lasers 单波长噪声273.Single quantum well 单量子阱274.Snell’s law 斯涅尔定律275.Solar cell 光电池276.Solid state photomultiplier 固态光复用器277.Spectral intensity 谱强度278.Spectral responsivity 光谱响应279.Spontaneous emission 自发辐射280.stimulated emission 受激辐射281.Terrestrial light 陆地光282.Theraml equilibrium 热平衡283.Thermal generation 热再生284.Thermal velocity 热速度285.Thershold concentration 光强阈值286.Threshold current 阈值电流287.Threshold wavelength 阈值波长288.Total acceptance angle 全接受角289.Totla internal reflection 全反射290.Transfer distance 转移距离291.Transit time 渡越时间292.Transmission coefficient 传输系数293.Tramsmittance 传输294.Transverse electric field 电横波场295.Tranverse magnetic field 磁横波场296.Traveling vave lase 行波激光器297.Uniaxial crystals 单轴晶体298.UnPolarized light 非极化光299.Wave 波300.W ave equation 波公式301.Wavefront 波前302.Waveguide 波导303.Wave n umber 波数304.Wave p acket 波包络305.Wavevector 波矢量306.Dark current 暗电流307.Saturation signal 饱和信号量308.Fringing field drift 边缘电场漂移plementary color 补色310.Image lag 残像311.Charge handling capability 操作电荷量312.Luminous quantity 测光量313.Pixel signal interpolating 插值处理314.Field integration 场读出方式315.Vertical CCD 垂直CCD316.Vertical overflow drain 垂直溢出漏极317.Conduction band 导带318.Charge coupled device 电荷耦合组件319.Electronic shutter 电子快门320.Dynamic range 动态范围321.Temporal resolution 动态分辨率322.Majority carrier 多数载流子323.Amorphous silicon photoconversion layer 非晶硅存储型324.Floating diffusion amplifier 浮置扩散放大器325.Floating gate amplifier 浮置栅极放大器326.Radiant quantity 辐射剂量327.Blooming 高光溢出328.High frame rate readout mode 高速读出模式329.Interlace scan 隔行扫描330.Fixed pattern noise 固定图形噪声331.Photodiode 光电二极管332.Iconoscope 光电摄像管333.Photolelctric effect 光电效应334.Spectral response 光谱响应335.Interline transfer CCD 行间转移型CCD336.Depletion layer 耗尽层plementary metal oxide semi-conductor 互补金属氧化物半导体338.Fundamental absorption edge 基本吸收带339.Valence band 价带340.Transistor 晶体管341.Visible light 可见光342.Spatial filter 空间滤波器343.Block access 块存取344.Pupil compensation 快门校正345.Diffusion current 扩散电流346.Discrete cosine transform 离散余弦变换347.Luminance signal 高度信号348.Quantum efficiency 量子效率349.Smear 漏光350.Edge enhancement 轮廓校正351.Nyquist frequency 奈奎斯特频率352.Energy band 能带353.Bias 偏压354.Drift current 漂移电流355.Clamp 钳位356.Global exposure 全面曝光357.Progressive scan 全像素读出方式358.Full frame CCD 全帧CCD359.Defect correction 缺陷补偿360.Thermal noise 热噪声361.Weak inversion 弱反转362.Shot noise 散粒噪声363.Chrominance difference signal 色差信号364.Colotremperature 色温365.Minority carrier 少数载流子366.Image stabilizer 手振校正367.Horizontal CCD 水平CCD368.Random noise 随机噪声369.Tunneling effect 隧道效应370.Image sensor 图像传感器371.Aliasing 伪信号372.Passive 无源373.Passive pixel sensor 无源像素传感器374.Line transfer 线转移375.Correlated double sampling 相关双采样376.Pinned photodiode 掩埋型光电二极管377.Overflow 溢出378.Effective pixel 有效像素379.Active pixel sensor 有源像素传感器380.Threshold voltage 阈值电压381.Source follower 源极跟随器382.Illuminance 照度383.Refraction index 折射率384.Frame integration 帧读出方式385.Frame interline t ransfer CCD 帧行间转移CCD 386.Frame transfer 帧转移387.Frame transfer CCD 帧转移CCD388.Non interlace 逐行扫描389.Conversion efficiency 转换效率390.Automatic gain control 自动增益控制391.Self-induced drift 自激漂移392.Minimum illumination 最低照度393.CMOS image sensor COMS 图像传感器394.MOS diode MOS 二极管395.MOS image sensor MOS 型图像传感器396.ISO sensitivity ISO 感光度。

超快光学超快光谱

Chopper
Chopped excite pulse train
The excite pulse periodically changes the sample absorption seen by the probe pulse.
Probe pulse train
Lock-in detector
What’s going on in spectroscopy measurements
The excite pulse(s) excite(s) molecules into excited states, which changes the medium’s absorption coefficient and refractive index.
DT(t) / T0 Da0 exp(–t /tex) L
0
Delay, t
Modeling excite-probe measurements
(cont’d)
3
Excite transition
2 Probe transition
1
0
More complex decays occur if intermediate states are populated or if the motion is complex. Imagine probing an intermediate transition, whose states temporarily fill with molecules on their way back down to the ground state:
Ultrafast laser spectroscopy: Why
Most events that occur in atoms and molecules occur on fs and ps time scales because the length scales are very small.

Ultrafast transient absorption spectroscopy principles and application to photosynthetic systems

REVIEWUltrafast transient absorption spectroscopy:principles and application to photosynthetic systemsRudi Berera ÆRienk van Grondelle ÆJohn T.M.KennisReceived:18February 2009/Accepted:5June 2009/Published online:4July 2009ÓThe Author(s)2009.This article is published with open access at Abstract The photophysical and photochemical reac-tions,after light absorption by a photosynthetic pigment–protein complex,are among the fastest events in biology,taking place on timescales ranging from tens of femto-seconds to a few nanoseconds.The advent of ultrafast laser systems that produce pulses with femtosecond duration opened up a new area of research and enabled investigation of these photophysical and photochemical reactions in real time.Here,we provide a basic description of the ultrafast transient absorption technique,the laser and wavelength-conversion equipment,the transient absorption setup,and the collection of transient absorption data.Recent appli-cations of ultrafast transient absorption spectroscopy on systems with increasing degree of complexity,from bio-mimetic light-harvesting systems to natural light-harvest-ing antennas,are presented.In particular,we will discuss,in this educational review,how a molecular understanding of the light-harvesting and photoprotective functions of carotenoids in photosynthesis is accomplished through the application of ultrafast transient absorption spectroscopy.Keywords Ultrafast spectroscopy ÁPhotosynthesis ÁLight-harvesting antennasAbbreviations(B)Chl (Bacterio)Chlorophyll BPheo Bacteriopheophtin EADS Evolution-associated difference spectra ESA Excited-state absorption FWHM Full-width at half maximum LHC Light-harvesting complex PSII Photosystem II RC Reaction center SADS Species-associated difference spectra SE Stimulated emissionIntroductionThe process of photosynthesis relies upon the efﬁcient absorption and conversion of the radiant energy from the Sun.Chlorophylls and carotenoids are the main players in the process.While the former are involved in light-har-vesting and charge separation process,the latter also play vital photoprotective roles.Photosynthetic pigments are typically arranged in a highly organized fashion to con-stitute antennas and reaction centers,supramolecular devices where light harvesting and charge separation take place.The very early steps in the photosynthetic process take place after the absorption of a photon by an antenna sys-tem,which harvests light and eventually delivers it to the reaction center (Van Grondelle et al.1994).Despite the enormous variety of photosynthetic organisms,the primary events leading to photosynthetic energy storage areremarkably similar (Sundstro¨m 2008).In order to compete with internal conversion,intersystem crossing,and ﬂuo-rescence,which inevitably lead to energy loss,the energyR.Berera ÁR.van Grondelle ÁJ.T.M.Kennis (&)Department of Physics and Astronomy,Faculty of Sciences,VU University Amsterdam,De Boelelaan 1081,1081HV Amsterdam,The Netherlands e-mail:john@nat.vu.nlPresent Address:R.BereraInstitute of Biology and Technology of Saclay,CEA (Commissariat a l’Energie Atomique),URA 2096CNRS (Centre National de la Recherche Scientiﬁque),91191Gif/Yvette,FrancePhotosynth Res (2009)101:105–118DOI 10.1007/s11120-009-9454-yand electron transfer processes thatﬁx the excited-state energy in photosynthesis must be extremely fast.In order to investigate these events,ultrafast techniques down to a sub-100fs resolution must be used.In this way,energy migration within the system as well as the formation of new chemical species such as charge-separated states can be tracked in real time.This can be achieved by making use of ultrafast transient absorption spectroscopy.The basic principles of this technique,instrumentation,and some recent applications to photosynthetic systems that involve the light-harvesting and photoprotective functions of carotenoids are described in this educational review.For earlier reviews on ultrafast spectroscopy,see e.g.,Jimenez and Fleming(1996),Groot and Van Grondelle(2008),and Zigmantas et al.(2008).Ultrafast transient absorption spectroscopyThe principle of ultrafast transient absorption spectroscopyThe process of energy transfer in a photosynthetic mem-brane typically takes place on a time scale from less than 100fs to hundreds of ps(Sundstro¨m et al.1999;Van Amerongen and Van Grondelle2001;Van Grondelle et al. 1994).The advent of ultrashort tunable laser systems in the early1990s has opened up a new and extremely fascinating area of research.Nowadays,the high(sub50fs)time resolution has made it possible to investigate the very early events taking place within a light-harvesting antenna in real time(Sundstro¨m2008).In transient absorption spectros-copy,a fraction of the molecules is promoted to an elec-tronically excited state by means of an excitation(or pump) pulse.Depending on the type of experiment,this fraction typically ranges from0.1%to tens of percents.A weak probe pulse(i.e.,a pulse that has such a low intensity that multiphoton/multistep processes are avoided during prob-ing)is sent through the sample with a delay s with respect to the pump pulse(Fig.1).A difference absorption spec-trum is then calculated,i.e.,the absorption spectrum of the excited sample minus the absorption spectrum of the sample in the ground state(D A).By changing the time delay s between the pump and the probe and recording a D A spectrum at each time delay,a D A proﬁle as a function of s and wavelength k,i.e.,a D A(k,s)is obtained.D A(k,s) contains information on the dynamic processes that occur in the photosynthetic system under study,such as excited-state energy migration,electron and/or proton transfer processes,isomerization,and intersystem crossing.In order to extract this information,global analysis procedures may be applied(see below).One advantage of time-resolved absorption spectroscopy over time-resolvedﬂuorescence is that with the former,the evolution of non-emissive states and dark states can be investigated.This is of particular importance in photosynthesis where carotenoid dark(non-emissive)states play a number of vital roles.In general,a D A spectrum contains contributions from various processes:(1)Theﬁrst contribution is by ground-state bleach.As afraction of the molecules has been promoted to the excited state through the action of the pump pulse,the number of molecules in the ground state has been decreased.Hence,the ground-state absorption in the excited sample is less than that in the non-excited sample.Consequently,a negative signal in the D A spectrum is observed in the wavelength region of ground state absorption,as schematically indicated in Fig.1(dashed line).(2)The second contribution is by stimulated emission.For a two-level system,the Einstein coefﬁcients for absorption from the ground to the excited state(A12)and stimulated emission from the excited to the ground state(A21)are identical.Thus,upon popula-tion of the excited state,stimulated emission to the ground state will occur when the probe pulse passes through the excited volume.Stimulated emission will occur only for optically allowed transitions and will have a spectral proﬁle that(broadly speaking)follows theﬂuorescence spectrum of the excited chromo-phore,i.e.,it is Stokes shifted with respect to the ground-state bleach.During the physical process of stimulated emission,a photon from the probe pulse induces emission of another photon from the excited molecule,which returns to the ground state.The photon produced by stimulated emission is emitted in the exact same direction as the probe photon,and hence both will be detected.Note that the intensity of the probe pulse is so weak that the excited-state population is not affected appreciably by this process.Stimulated emission results in an increase of light intensity on the detector,corresponding to a negativeD A signal,as schematically indicated in Fig.1(dottedline).In many chromophores including bacteriochlo-rophyll(BChl),the Stokes shift may be so small that the stimulated emission band spectrally overlaps with ground-state bleach and merges into one band. (3)The third contribution is provided by excited-stateabsorption.Upon excitation with the pump beam, optically allowed transitions from the excited(pop-ulated)states of a chromophore to higher excited states may exist in certain wavelength regions,and absorption of the probe pulse at these wavelengths will occur.Consequently,a positive signal in the D A spectrum is observed in the wavelength region of excited-state absorption(Fig.1,solid line).Again,the intensity of the probe pulse is so weak that the excited-state population is not affected appreciably by the excited-state absorption process.(4)A fourth possible contribution to the D A spectrum isgiven by product absorption.After excitation of the photosynthetic,or more generally photobiological or photochemical system,reactions may occur that result in a transient or a long-lived molecular state,such as triplet states,charge-separated states,and isomerized states.The absorption of such a(transient)product will appear as a positive signal in the D A spectrum.A ground-state bleach will be observed at the wave-lengths where the chromophore on which the product state resides has a ground-state absorption.A well-known example of such a transient product state is the accessory bacteriochlorophyll(BChl)anion in the bacterial reaction center(RC),which acts as a transient intermediate in the electron transfer process from the primary donor P to the bacteriopheophytin(BPheo).The rise and decay of this species can be monitored through its speciﬁc product absorption at 1,020nm(Arlt et al.1993;Kennis et al.1997a). Pulse duration,time resolution,and spectral selectivity Laser pulses as short as5fs are now available for transient absorption spectroscopy(see,e.g.,Cerullo et al.(2002); and Nishimura et al.(2004)).A short pulse duration D t implies a large spectral bandwidth D v according to relation D t D v=0.44for Gaussian-shaped pulses.This relation is known as the time–bandwidth product.For instance,a10-fs pulse with a center wavelength of800nm has a spectral bandwidth of4.491013Hz at full-width at half maximum (FWHM),which corresponds to about100nm in this wavelength region.Thus,one has to make a trade-off between time resolution and spectral selectivity.Consider the example of the bacterial RC,which has the primary donor absorbing at860nm,the accessory BChls at 800nm,and the BPheos at760nm.With a10-fs pulse at 800nm,one would simultaneously excite all the cofactors. In order to selectively excite one of the cofactor pairs to study its excited-state dynamics,spectral narrowing to *30nm is required,which implies a longer excitation pulse of*30fs(Streltsov et al.1998;Vos et al.1997).For the photosystem II(PSII)RC,where the energy gaps between the pigments are signiﬁcantly smaller,the exci-tation bandwidth has to be narrowed even more to\10nm for selective excitation,with corresponding pulse durations of*100fs(Durrant et al.1992;Groot et al.1997).On very fast timescales,transient absorption signals have contributions from processes additional to those described in the previous section.These non-resonant contributions are often lumped together under the terms‘‘coherent arti-fact’’and‘‘cross-phase modulation.’’As transient absorp-tion signals result from light–matter interaction through the third-order non-linear susceptibility v(3)(Mukamel1995), non-sequential light interactions that do not represent pop-ulation dynamics of electronic states will contribute to the signals.Such undesired signals can be ignored by excluding the initial phases of the femtosecond dynamics from the data interpretation and analysis.On the other hand,they may be explicitly included in the analysis by considering their physical origin.In such a case,assumptions need to be made about the lineshapes and dephasing times of the chromo-phore in question(Novoderezhkin et al.2004).Cross-phase modulation effects are due to a change in the index of refraction of solvent and cuvette induced by the pump beam and give rise to oscillatory patterns around zero delay (Kovalenko et al.1999).These artifacts can in principle be subtracted from the data by recording an experiment in a cuvette with the solvent.Equipment:ampliﬁed Ti:sapphire laser systemsand optical parametric ampliﬁersGenerally speaking,two types of ultrafast transient absorption spectroscopy setups are widely used today for photosynthesis research,distinguished by the repetition rate and pulse energies at which they operate:theﬁrst type involves systems with a repetition rate of1–5kHz with a relatively high pulse energy.The second type involves systems with a repetition rate in the range40–250kHz with a relatively low pulse energy.In addition,the direct or cavity-dumped output from a Ti:sapphire oscillator has frequently been employed for transient absorption spec-troscopy,but will not be discussed here(Arnett et al.1999; Kennis et al.1997b;Nagarajan et al.1996;Streltsov et al. 1998;Vulto et al.1999).Theﬁrst type of spectroscopy typically provides the experimenter with excitation energies of5–100nJ,which when focused on150–200l m diameter(the regular focus-ing conditions in our laboratory)typically results in2–20% of the molecules being promoted to the excited state.This value is only approximate,since the accurate estimate of the excitation density depends on several factors,namely,the exact size of the focus,the concentration of the chromoph-ores,and their extinction coefﬁcient.The relatively high excitation densities achieved with these systems make them suitable to study complexes with a relatively small number of connected pigments such as pigments in solution(Billsten et al.2002;Cong et al.2008;De Weerd et al.2003;Nied-zwiedzki et al.2007;Polivka et al.1999),isolated reaction centers(De Weerd et al.2002;Holzwarth et al.2006a, 2006b;Wang et al.2007),isolated light-harvesting antenna complexes(Croce et al.2001;Gradinaru et al.2000,2001; Ilagan et al.2006;Krueger et al.2001;Papagiannakis et al. 2002,2003;Polı´vka et al.2002;Polivka and Sundstro¨m 2004;Zigmantas et al.2002),artiﬁcial antenna systems (Berera et al.2006,2007;Kodis et al.2004;Pan et al.2002), and photoreceptor proteins that bind only a single chromo-phore(Kennis and Groot2007;Wilson et al.2008).With appropriate detection schemes that involve multichannel detection on a shot-to-shot basis,signal detection sensitiv-ities of*10-5units of absorbance over a broad wavelength range can be achieved,implying that molecular species with a small extinction coefﬁcient or that accumulate in very low (transient)concentrations can be detected(Berera et al. 2006;Wilson et al.2008).A drawback of a1–5-kHz system is that with its relatively high excitation densities,multiple excited states may appear in a single multichromophoric complex,resulting in singlet–singlet annihilation processes among(B)Chls(Van Grondelle1985).With the laser systems that operate at40–250kHz,a lower pulse energy can be used for excitation with respect to the kHz systems owing to their higher repetition rate,which allows more laser shots to be averaged per unit time. Typically,pulse energies of0.5–10nJ are used,roughly corresponding to excited-state populations of\1–10%. Under the right circumstances,detection sensitivities of *10-6units of absorbance can be achieved.Accordingly, this kind of system has been used to study exciton migra-tion in large systems with many connected pigments such as chloroplasts and light-harvesting complex(LHC)II aggregates(Holt et al.2005;Ma et al.2003;Ruban et al. 2007).In addition,it has been used to examine exciton migration in isolated LH complexes under annihilation-free conditions(Monshouwer et al.1998;Novoderezhkin et al. 2004;Palacios et al.2006;Papagiannakis et al.2002). Drawbacks of this type of systems involve the shorter time between pulses(4–20l s),which may lead to the build-up of relatively long-lived species such as triplet or charge-separated states.In addition,multichannel detection on a shot-to-shot basis has been limited to14channels at such high repetition rates(Ruban et al.2007),although signiﬁ-cant strides are currently being made in our laboratory to resolve this limitation.Figure2shows a scheme of an ultrafast transient absorption setup,as it exists today in the Biophysics Lab-oratory of the Laser Center at the Vrije Universiteit(LCVU) in Amsterdam,The Netherlands.A broadband oscillator (Coherent Vitesse)generates pulses of*30fs duration with a wavelength of800nm,a bandwidth of*35nm at a repetition rate of80MHz.The pulses from the oscillator are too weak to perform any meaningful spectroscopy and therefore have to be ampliﬁed.Femtosecond pulse ampli-ﬁcation is not a trivial matter because at high energies,the peak power in a femtosecond pulse becomes so high that ampliﬁcation and pulse-switching media such as crystals and Pockels cells easily get damaged.A Pockels cell is an electro-optical device containing a crystal,such as potas-sium dihydrogenphosphate(KH2PO4),capable of switching the polarization of light when an electrical potential differ-ence is applied to it.In this way,the amount of stimulated emission from the laser cavity can be controlled.For this reason,femtosecond pulse ampliﬁcation is carried out through the chirped-pulse ampliﬁcation principle:the pulse from the oscillator(hereafter,referred to as‘‘seed pulse’’)is ﬁrst stretched to*200ps by a stretcher,which temporally delays the‘‘blue’’wavelengths within the pulse bandwidth of*35nm with respect to the‘‘red’’wavelengths by means of a grating pair.Then,the seed pulse is coupled into a regenerative ampliﬁer(Coherent Legend-UltraShort Pulse (USP)).There,the seed pulse travels through a Pockels cell which sets its polarization in such a way that it becomes trapped within the ampliﬁer’s cavity.On traveling back and forth in the cavity,it passes through a Ti:sapphire crystal that is pumped at1-kHz repetition rate by a diode-pumped Nd:YLF pump laser at527nm(Coherent Evolution,30W).At each passage through the crystal,the trapped seed pulse is ampliﬁed until saturation is reached.Then,the Pockels cell switches the polarization of the ampliﬁed pulse which results in its ejection from the ampliﬁer.The ampliﬁed pulse is compressed to*45fs by temporally synchronizing the ‘‘blue’’and‘‘red’’wavelengths within the pulse bandwidth, essentially the reverse of the‘‘stretching’’procedure.At this point,the output from the laser system is a40-fs pulse at an energy of2.5mJ,a center wavelength of800nm,a band-width of30nm,and a repetition rate of1kHz.In order to perform transient absorption spectroscopy with a Ti:sapphire laser alone,one is restricted to a wavelength region for the excitation pulse around800nm, allowing only the study of some BChl a-containing systems (Arnett et al.1999;Kennis et al.1997b;Nagarajan et al. 1996;Novoderezhkin et al.1999;Streltsov et al.1998; Vulto et al.1999).In order to shift the wavelength to other parts of the visible and near-IR spectra,optical parametric ampliﬁers(OPAs)or optical parametric generators(OPGs) are typically used.In an OPA,non-linear birefringent crystals such as beta barium borate(BBO)are pumped by the direct output of the ampliﬁed laser system at800nm or frequency-doubled pulses at400nm.The pump is tempo-rally and spatially overlapped with a white-light continuum in the crystal,and depending on the angle between the laser beam and the symmetry axis of the crystal,two particular wavelengths of the white-light continuum called‘‘signal’’and‘‘idler’’are ampliﬁed through the second-order non-linear polarizability of the crystal,of which the signal has the shortest wavelength and is routinely selected for further use.Since pump,signal,and idler beams have different polarizations,the group velocity of pump,signal,and idler beams can be made equal by varying the angle between the laser beam and the symmetry axis of the birefringent crystal.This allows energy from the pump beam to be converted to the signal and idler beams over a large propagation length up to millimeters.This is the so-called phase-matching condition.Conservation of energy requires that the sum of the frequencies of signal and idler add up to the frequency of the pump beam.Thus,800-nm-pumped OPAs operate in the near-InfraRed(IR)(1,100–1,600nm for the signal)while400-nm-pumped OPAs operate in the visible(475–750nm for the signal)ing the output of an OPA as a basis,essentially all wavelengths from the UltraViolet(UV)to mid-IR can be generated at relatively high pulse energies by using non-linear mixing processes such as frequency-doubling,sum-frequency generation,and difference-frequency generation in suitable non-linear crystals.Obviously,visible and near-IR light are the most useful wavelengths for the study of photosynthetic systems.In addition,mid-IR wavelengths are very useful for probing molecular vibrations of chlorophylls and carotenoids(Groot et al.2005,2007).The pulse duration out of the OPA roughly corresponds to that of the ampliﬁed Ti:sapphire laser system.The pulse energy from our regenerative laser ampliﬁer of2.5mJ allows simultaneous pumping of several OPAs.The latter option is important for experiments that require multiple pump pulses,such as pump–dump or pump–repump experiments(Kennis et al. 2004;Larsen et al.2003;Papagiannakis et al.2004).The transient absorption setupIn order to vary the time delay between the excitation and probe pulses,the excitation pulse generated by the OPA is sent through an optical delay line,which consists of a retroreﬂector mounted on a high-precision motorized computer-controlled translation stage.The translation stage employed in our experiments has an accuracy and repro-ducibility of0.1l m,which corresponds to a timing accu-racy of0.5fs.The delay line can be moved over80cm, implying that time delays up to5ns can be generated between excitation and probe beams.The excitation beam is focused in the sample to a diameter of130–200l m and blocked after the sample.In most cases,the polarization of the pump beam is set at the magic angle(54.7°)with respect to that of the probe to eliminate polarization and photoselection effects(Lakowicz2006).For the detection of the pump-induced absorbance changes,a part of the ampliﬁed800-nm light is focused on a sapphire or calciumﬂuoride plate(though other materials such as quartz,MgF2,water,and ethylene glycol can also be used)to generate a white-light continuum.In the absence of special precautions,the white-light continuum may range from*400to*1,100nm(depending on the material)and be used as a broadband probe;its intensity is so weak that it does not transfer an appreciable population from the ground to the excited state(or vice versa).It is focused on the sample to a diameter slightly smaller than the pump,spatially overlapped with the pump,collimated, and sent into a spectrograph.There,it is spectrally dis-persed and projected on a silicon diode array that consists of tens to hundreds of elements.The diode array is read out by a computer on a shot-to-shot basis,in effect measuring an absorption spectrum with each shot.Under some experimental conditions,detection with a diode array is not possible or appropriate.For instance,for many experiments in the near-IR and the UV,other detector types need to be employed that,in combination with the white-light continuum intensities at those wave-lengths,lack the sensitivity required for array detection.In these cases,single wavelength detection is often employed. In the mid-IR(*3–10l m),mercury cadmium telluride (MCT)arrays that consist of32or64elements are avail-able(Groot et al.2007).Another detection method in the visible spectrum employs a charge-coupled device(CCD) detector.Frequently,a reference beam is used to account for shot-to-shot intensityﬂuctuations in the white-light continuum.In such a case,the white-light continuum beam is split in two beams,the probe and the reference.The probe is overlapped with the pump beam in the sample, while the reference beam is led past the sample(or through the sample past the excited volume).The probe and ref-erence beams are then projected on separate diode arrays.During data collection,the probe beam is divided by the reference beam,which may lead to improved signal to noise because the intensityﬂuctuations of the white-light continuum are eliminated.By the nature of the white-light generation process,the white light is‘‘chirped’’on generation,i.e.,the‘‘blue’’wavelengths are generated later in time than the‘‘red’’wavelengths.The exact temporal properties depend on the speciﬁc generation conditions.Hence,the white-light continuum has an‘‘intrinsic’’group-velocity dispersion. When traveling through optically dense materials such as lenses and cuvettes,the group velocity dispersion in the white light readily increases to picoseconds.This effect can be minimized by using parabolic mirrors for collimation and focusing of the white-light beam between its point of generation and the sample.The group velocity dispersion may be accounted for in the data analysis and described by a polynomial function.Alternatively,the white-light con-tinuum can be compressed by means of a grating pair or prism pair in such a way that the‘‘red’’and‘‘blue’’wavelengths in the probe beam coincide in time.The instrument response function of this particular tran-sient absorption apparatus,which can be measured by fre-quency mixing in a non-linear crystal placed at the sample spot or by the transient birefringence in CS2or water,can usually be modeled with a Gaussian with a FWHM of 120fs.If required,the white-light continuum can be com-pressed down to*10fs by means of a grating pair or prism pair;in such a case,the instrument response function is generally limited by the duration of the pump pulse.For measurements at room temperature,the sample is placed in a1–2-mm quartz cuvette which is either con-nected to aﬂow system or mounted on a shaker to prevent exposure of the same excited volume to multiple laser shots and to prevent sample degradation.Collection of transient absorption spectraA transient absorption experiment proceeds as follows:the time delay between excitation and probe beams isﬁxed. Before reaching the sample,the excitation beam(that delivers a pulse every1ms)passes through a mechanical chopper that is synchronized to the ampliﬁer in such a way that every other excitation pulse is blocked.Thus,alter-nately the sample is being excited and not excited.Con-sequently,the white-light continuum that is incident on the detector diode array alternately corresponds to a‘‘pumped’’and‘‘unpumped’’sample,and the detector alternately measures the intensity of the probe beam of a‘‘pumped’’and‘‘unpumped’’sample,I(k)pumped and I(k)unpumped. I(k)pumped and I(k)unpumped are stored in separate buffers (while keeping the time delay between pump and probe ﬁxed),and a number of shots that is sufﬁcient for anacceptable signal-to-noise ratio is measured,usually103–104.With the shot-to-shot detection capability of the multichannel detection system,particular spectra that deviate from the average(‘‘outliers’’)can in real time be rejected during data collection,signiﬁcantly improving signal-to-noise ratio.A second white-light beam(the ref-erence beam)not overlapping with the pump pulse can also be used to further increase the signal-to-noise ratio.From the averaged values of I(k)pumped and I(k)unpumped,an absorbance difference spectrum D A(k)is constructed according toD AðkÞ¼ÀlogðIðkÞpumped =IðkÞunpumpedÞ:Then,the delay line is moved to another time delay between pump and probe,and the above procedure is repeated.In total,absorbance difference spectra at approximately100–200time points between0fs and*5ns are collected, along with absorbance difference spectra before time zero to determine the baseline.In addition,many spectra are collected around the time that pump and probe pulse overlap in time(‘‘zero delay’’)to enable accurate recording of the instrument response function.This whole procedure is repeated several times to test reproducibility,sample stability,and long-termﬂuctuations of the laser system.In this way,an entire dataset D A(k,s)is collected. Anisotropy experiments in transient absorption spectroscopyIn photosynthetic antennae and reaction centers,the pig-ments are bound in a well-deﬁned way.Energy and elec-tron transfer processes and pathways can be speciﬁcally assessed through the use of polarized excitation and probe beams.The time-dependent anisotropy is deﬁned asrðtÞ¼ðD A kðtÞÀD A?ðtÞÞ=ðD A kðtÞþ2D A?ðtÞÞ:With D A k(t),the time-dependent absorbance difference signal with pump and probe beams is polarized parallel, and with D A\(t),the time-dependent absorbance difference signal with pump and probe beams is polarized perpen-dicular.In light-harvesting antennae,the decay of r(t) indicates the elementary timescales of exciton migration, be it through incoherent hopping or exciton relaxation (Kennis et al.1997b;Nagarajan et al.1996;Novoderezhkin et al.1998;Savikhin et al.1994,1998,1999;Vulto et al. 1999;Vulto et al.1997).Energy transfer or exciton relaxation processes often occur among(pools of)Chls that have their absorption maxima at similar wavelengths. Consequently,these processes are associated with small spectral shifts of the D A spectra and are there-fore difﬁcult to observe under magic angle detection con-ditions.Through time-resolved anisotropy experiments,the timescales of such fast exciton migration events can accurately be determined.Data analysisIn time-resolved spectroscopic experiments,the very large amounts of data collected can be analyzed by global and target analysis techniques(Van Stokkum et al.2004).A typical time-resolved experiment D A(k,s)in fact consists of a collection of thousands of data points,i.e.,tens to hun-dreds wavelengths times one to two hundred data points.In order to extract valuable information,one could simply take slices of the data;for instance,one could take one wavelength and look at its evolution in time(a so-called kinetic trace),or one could plot the signal at different wavelengths for a given time point(a D A spectrum).This is normally theﬁrst stage of the data analysis where the experimentalist has a glimpse of an expected(or unex-pected)process.The next step in the data analysis is to apply the so-called global analysis techniques,in an attempt to distill the overwhelming amount of data into a relatively small number of components and spectra.In the most basic model,the femtosecond transient absorption data are globally analyzed using a kinetic model consisting of sequentially interconverting evolution-associated dif-ference spectra(EADS),i.e.,1?2?3?ÁÁÁin which the arrows indicate successive monoexponential decays of increasing time constants,which can be regarded as the lifetime of each EADS.Theﬁrst EADS correspond to the time-zero difference spectrum.This procedure enables a clear visualization of the evolution of the(excited)states of the system.Based on the insight obtained from this model and from the raw data,one can then take a further step in the analysis and apply a so-called target kinetic scheme. The EADS that follow from the sequential analysis are generally made up from a mixture of various molecular species.In general,the EADS may well reﬂect mixtures of molecular states.In order to disentangle the contributions from these molecular species and obtain the spectrum signature of the‘‘pure’’excited-and product state inter-mediates(the so-called species-associated difference spectra,SADS),a speciﬁc kinetic model must be applied in a so-called target analysis procedure.In this way,the energy and electron transfer mechanisms can be assessed in terms of a number of discrete reaction intermediates.A comprehensive review of global and target analysis tech-niques has been published(Van Stokkum et al.2004).In the next section,we illustrate a few examples of time-resolved experiments and data analysis.We will start with the description of elementary energy transfer processes in artiﬁcial systems followed by more complex examples in natural light-harvesting compounds.。

光电英语词汇(U)

光电英语词汇(U)光电英语词汇(U)光电英语词汇(U)u-band u[吸收光]带u-bolt u型螺栓u-center(uniform chromaticity scale) diagra 均匀色品图u-form tube u型管ulbricht integrating photometer 乌布利希积分光度计ulbricht sphere 布利希球（积分光度计）ultex 整块双焦点镜ultifocus lens 多焦点透镜ultimate (1)最後的(2)极限的(3)基本的ultimate particles 基本粒子ultimate pressure 极限压强ultimate range 极限范围ultimate ray 最後射线ultimate vacuum 极限真空ultiplicator 乘数ultra achromatic lens 超消色差透镜ultra bright 超亮的ultra narrowband filters 超窄频滤光镜ultra precise measurement 超精密测量ultra purity 超纯度ultra radio frequency 超射频[率]ultra trace 超痕量ultra-light-weight 超轻重量ultra-optimeter 超级光学计ultra-photometer 不可见光光度计ultra-portable camera 超小型电视摄像机ultra-rapid lens 超大孔径物镜ultra-red (1)红外的(2)红外线ultra-red absorption spectrometry 红外线吸收分光光度学ultra-red ray 红外线ultrafast 超速的ultrafast coherent phenomena 超速相干现象ultrafast light pulse 超速光脉冲ultrafast relaxation 超速弛豫ultrafiltration 超滤作用ultraharmonic 高次谐波[的]ultraharmonics 高次谐波ultrahigh frequency 超高频ultrahigh resolution 超高分辨率ultrahigh speed photographic instrument 超高速照相器械ultrahigh speed photography 超高速摄影术ultrahigh vacuum 超高真空ultralow frequency 超低频ultraluminescence 紫外荧光，紫外光ultramarine blue 绀青ultramicrometer 超微测试计ultramicroscope 超显微镜ultramicroscopic 超显微[的]ultramicroscopy 超显微术ultramicrowave 超微波ultraphosphate 过磷酸ultraphotic rays 不可见射线ultraplane microscope projection lens 超平场显微镜投影镜头ultraporcelain 超高频瓷ultrarays 宇宙线ultrascope image tube 紫外显像管ultrashort laser pulse 超短激光脉冲ultrashort light pulse 超短光脉冲ultrashort pulse 超短脉冲ultrashort synchronized laser pulse 超短同步激光脉冲ultrashort wave (usw)超短波ultrasil 超硅，高硅ultrasonic (1)超声的(2)超声速的ultrasonic bragg cell 超声喇格盒ultrasonic bragg diffraction 超声布喇格衍射ultrasonic cleaning 超声清洗ultrasonic control 超声控制ultrasonic cross grating 超声交叉光栅ultrasonic detecdor 超声[波]检测器ultrasonic flow 超声速流ultrasonic grating 超声光栅ultrasonic grating constant 超声光栅常数ultrasonic hologram 超声全息图ultrasonic holography 超声全息术ultrasonic lens 超声透镜ultrasonic light diffraction 超声致光衍射ultrasonic method 超声波法ultrasonic modulator 超声调制器ultrasonic q-switch 超声q开关ultrasonic scanner 超声扫描器ultrasonic space grating 超声空间光栅ultrasonic standing wave 超声驻波ultrasonic switch 超声开关ultrasonic washing 超声清洗ultrasonic wave 超声波ultrasonic-wave grating 超声波光栅ultrasonics 超声学ultrasound 超音波ultrasound holography 超声全息术ultrathin laser 超薄激光器ultrathing microscope 超薄显微镜ultraviolet (1)紫外的(2)紫外线ultraviolet absorbing filters 紫外吸收滤光镜ultraviolet absorption spectrometry 紫外吸收分光光度学ultraviolet and visible spectrophotometer 紫外可见分光光度计ultraviolet astronomical photometry 紫外天文光度学ultraviolet band 紫外区，紫外波段ultraviolet bandpass filter 紫外带通滤光片ultraviolet catastrophe 紫外灾变ultraviolet curing equipment 紫外线硬化设备ultraviolet cutoff 紫外线截止ultraviolet detection 紫外辐射探测ultraviolet dosimeter 紫外线剂量计ultraviolet impulse optics 紫外线脉冲光学ultraviolet injury 紫外线损伤ultraviolet lamp 紫外[线]灯ultraviolet laser (uv laser)紫外激光器ultraviolet lenses 紫外线透镜ultraviolet light (1)紫外线(2)紫外[线]轴射ultraviolet light sources 紫外线光源ultraviolet materials 紫外线材料ultraviolet microscope 紫外线显微镜ultraviolet photodiodes 光二极体(紫外光) ultraviolet photography 紫外线照相术ultraviolet photometer 紫外线度计ultraviolet photomicrography 紫外线显微照相术ultraviolet photon 紫外光子ultraviolet polarimeter 紫外线旋光仪，紫外偏振计ultraviolet pumping 紫外线抽运ultraviolet radiation 紫外辐射ultraviolet radiation standard 紫外辐射标准ultraviolet ray 紫外线ultraviolet refractometry 紫外折射测量法ultraviolet sensitive paper 紫外光敏纸ultraviolet spectrogram 紫外光谱图ultraviolet spectrograph 紫外摄谱仪ultraviolet spectrometer 紫外线分光计ultraviolet spectrum 紫外光谱ultraviolet telescope 紫外望远镜ultraviolet transition 紫外跃迁ultraviolet transmitting filters 紫外透过滤光镜ultraviolet vidicon 紫外光导摄像管ultraviolet wavelength 紫外线波长ultraviolet-emitting source 紫外线发射源ultraviolet-induced 紫外感应的ultraviolet-transmitting filter 紫外透射滤光片ultrawide angle lens 特广角物镜ultrawide angle photographic lens system 特广角照相透镜系统umber 赭色umbra (复数:umbre)本影umen-second 流明秒umweganregung 迂回激发un shielded telescope 无屏蔽望远镜un silvered plate 非镀银板unaberrated system 无像差系统unactivated 未激活的unactivated state 未激活态unadjusted eye 肉眼unaided eye 肉眼unannealed 未退火的unbacked film 无衬胶卷unbalance 失衡，不平衡unbalanced sight 非平衡瞄准unbiased (1)不偏的(2)未加偏压的unblanking [信号]开启，开锁unblemished surface 无[瑕]疵表面unblocking 卸模unbound electron 无束缚电子uncertainty (1)不确定性(2)不精确性uncertainty condition 测不准条件uncertainty principle 测不准定理uncertainty relation 测不准关系uncharged particle 不带电粒子unchecked 未经校核的unchirped 无啁啾效应的unchopped radiometer 未斩光辐射计unclad fibre 无色层纤维uncoated (1)未镀膜的(2)无履盖的uncoated laser 未镀膜激光器uncoated lens 无镀膜透镜uncoaxiality 不同轴性uncollimated 未准直的unconditional probability 无条件概率unconnected 不连接的uncontrolled 不受控制的uncoupled 解耦合的uncoupled particle 解耦合粒子uncut lens 未加工透镜undamped spiking 无阻尼尖峰undamped wave (1)无阻尼波(2)等幅波undeflected 未偏转的under exposure 曝光不足，欠曝光under-active 活化不足的under-exposed 曝光不足的，欠曝光的underbalance 欠平衡，欠平衡的undercharge 充电不足[的] undercolour removal (ucr)底色去除undercompensation 欠补偿，补偿不足undercorrected lens 校正不完全透镜undercorrection 校正不足undercoupling 欠耦合，耦合不足undercurrent (1)电流不足(2)暗流，潜流underdamping 阻尼不足，欠阻尼underdense 欠密的underdeterminant 子行例式underdevelopment 显影不足underexcitation 欠激发，内激励underlagged [相位]滞後欠调underload 欠载undermined-phase technique [偏振态测量]不定相位技术undermodulation 欠调制underquenching 淬火不足undersaturation 欠饱和undersea ranging 海下测距，水下测距undershoot (1)下冲(2)负脉冲信号underspeed 速度不足underswing 负尖峰underwater camera 水下照相机underwater laser radar 水下激光雷达underwater tv camera 水下电视摄像机underwater visibility 水下能见度underwater vision 水下视觉undeveloped 未显影的undeviated light 未偏射光undiffracted wave 未衍射波undissolved substance 不溶物undistorted 无畸变的undistorted image 无畸变图像，不失真图像undistorted wave 无畸变波undisturbed 无扰动的undoped 无掺杂的undoped diode 非掺杂二极管undoped single crystal 非掺杂单晶体undosed 未经照射的undulating light 脉动光undulation 波动，起伏undulatory 波动的unearthed 未接地的uneven front 不整齐前沿uneven grain 不均匀颗粒unevenness 不均匀性unevenness of exposure 曝光不均匀性unexcited 未激励的unexcited level 未激发能级unexcited state 未激发态unexposed 未曝光的unfilled level 未满能级unfilled shell 未填满壳层unfinished 未抛光的unfixed point 不定点unfocused 未聚焦的unfocused laser 未聚焦激光器unfocused light 未聚焦光unfocused surface 未研磨面unguided 无制导的unharmonic oscillator 非谐振荡器uniaxial 单轴的uniaxial crystal 单轴晶体uniaxial negative crystal 负单轴晶体uniaxial nonlinear single crystal 单轴非线性单晶uniaxial orientation 单轴取向unicolor 单色unicontrol 单向控制unidimensional 一维[的]unidimensional hologram 一维全息图unidirection 单向，同一方向unidirectional 单向的unidirectional traveling wave 单向行波unidirectional-information flow 单向信息流unified coarse thread (unc)统一标准粗牙螺纹unified fine thread (unf)统一标准细牙螺纹uniform 均匀uniform acceleration 匀加速度uniform amplitude 等幅uniform chromaticity scale diagram 均匀色品图uniform color space 均匀色空间uniform density 均匀密度uniform diffuse transmission 均匀扩散传输uniform distribution 均匀分布uniform field kerr cell 均[匀]场克尔盒uniform illumination 均匀照明uniform lightness-chromaticness scale (ulcs)均匀亮度–色度标uniform point source 均等点源uniform slope 等斜牵uniform velocity 匀速度uniformity 均匀性uniformity of illumination 照明均匀性uniformity of light 光的均匀性uniformization 均匀化uniformly diffusing surface 均匀散射面uniguide slit 单向狭缝unijunction 单结unijunction transistor 单结[晶体]管unilateral 单边的，单向的unilateral conduction 单向导电unilateral transducer 单向换能器unilaterally adjustable 单向可调的unilayer 单分子层unimodal laser 单模激光器uninsulated 未绝缘的union (1)连接(2)活接头unionized 未电离的uniphase 单相[的]uniphase mode 单相模uniplanar orientation 单面取向unipolar 单极的uniqe (1)唯一的(2)单值的uniqueness of solution 解的唯一性uniqueness theorem 唯一性定理unit (1)单位(2)单元(2)设备，装置，机构(4)组合，组合件，部件unit amplitude 单位振幅unit area 单位面积unit bore system 基孔制unit brightness 单位亮度unit cell 晶胞unit charge 单位电荷unit cube 单位立方体unit error 单位误差unit function 单位函数unit length 单位长度unit load 单位负载unit mass 单位质量unit matrix 单位[矩]阵unit of capacity 容量单位unit of error 误差单位unit of measurement 计量单位unit of time 时间单位unit of weight 重量单位unit plane 单位面，主位面unit pressure 单位压力unit pulse 单位脉冲unit resistance 单位电阻unit shaft system 基轴制unit step function 单位阶跃函数unit strain 单位应变unit stress 单位应力unit system 单位制unit time 单位时间unit vector 单位失量unit-power sighting telescope 一倍瞄准[望远]镜unitarityㄠ正性unitaryㄠ正的unitary matrixㄠ正矩阵unitary operatorㄠ正算符unitary representationㄠ正表示unitary scattering factorㄠ正散射因数unity emissivity 完全发射unity transmittance 单一透射比univalent 单价的universal angel block 万能角规universal apparatus 通用仪器universal bevel protractor 通用斜角规universal dividing head 万能分度头universal finder 万能取景器universal focus lens 固定焦聚焦透镜universal gear tester 万能测齿仪universal gravitation 万有引力universal horizontal metroscope 万能卧式测量仪universal joint mechanism 万向节机构universal joint spider 万向节十字头universal laser 通用激光器universal length measuring machine 万能测长仪universal lens interferometer 通用透镜干涉仪universal level 通用水准仪universal machine tools 通用机床universal measuring head 万能测量头universal measuring microscope 万能测量显微镜universal meter 万用表universal microscope 万能型显微镜universal motor 交流真流两用电动机universal photomicroscope 万能照相显微镜universal refractometer 万能折射计universal scale holder 万能尺架universal sine-rule 万能正弦规尺universal stage 万能[旋转]工具作台universal stand 万能台，多用座universal theodolite 通用经纬仪universal type 万能型，通用型univibrator 单稳态触发器，单稳态多谐振荡器univoltage lens 单电压透镜unknown (1)未知的(2)未知数unlimited exposure 无限曝光unmagnetized 未磁化的unmoderated 未减速的，未慢化的unmodulated 未调制的unoccupied level 未满能级unpacking 拆箱，拆封unperturbed 未扰动的unplugged 非堵塞的，非封开的unpolarized 未偏振的，未极化的unpolarized light 非偏振光unpredictability 不可预知性unquantized 未量子化的unreflected 无反射的，未反射的unrelated colo[u]r 孤立色unreliability 不可靠性unresolved lines 未分离谱线unresonant system 非分振系统unsaturation 未饱和unsealed system 非密封系统unshaded area 无阳影区unsharp 不清晰的unsharp image 不清晰图像unsharp line 模拟线unshielded 无屏蔽的，无防护的unstability 不稳定的unstable 不稳定的unstable optical resonator 非稳定光学共振腔unsteady 不稳定的unsteady state 非稳态unsuppressed sideband 未抑制的旁通带unsurveyed 未测量的unswept pumping 固定频率抽运unsymmetrical 非对称的untitled 无倾斜的unxoned metal lens 未分区金属透镜（天线）unzoned lens 未分区透镜（天线）up-down counter 可逆计数器upconversion (1)上转换(2)升频转换upconverter (1)上转换器(2)升频器，上变频器upconverting laser 升频转换激光器upfloated 浮起的upper film loop 上片环upper hemispherical flux 上半球光通量upper laser level 激光高能极，激光上能级upper limb 上缘upper limit (1)上限尺寸，最大尺寸(2)上限upper margin 上边，顶边upper right 右上方upper side band wave 上边带波upper side frequency 上边频upper state 上态upper state relaxation 高能态弛豫upper-hybrid-resonace absorption 上混合共振吸收upright 真立的upright image 正立像upright post 立柱upright projection 正立投影upscattering 向上散射upside 上部，上面upside down 颠倒，倒转upstage 顶级upstream 上游的，上流的upstream ionization 上游离子化upwash 上洗upwelling 喷出，涌出uranin 荧光素钠uraninite 沥青铀矿uranium (u)铀uranium glass 铀玻璃ureterscope 输尿管镜usability 使用性能usable aperture 有效孔径，可用孔径useful diameter 有效直径useful work 有效功utiliscope 工业电视装置utilization factor 利用系数utrecht solar eclipse expedition 乌得勒支日食考察uv (ultra-violet) detector 紫外[光]检测器uv dye laser 紫外染料激光器uv filter 紫外滤光片uv irradiation 紫外[线]辐照uv lamp 紫外线灯uv laser 紫外缴光器uv light (1)外光线(2)紫外[线]辐射uv photostat 紫外直接影印机(2)\紫外直接影印制品(3)紫外照相复制uv scanner 紫外扫描器uv-nitrogen laser 紫外氮激光器uv-transmitting 紫外透射的uv-visible photoemitter 紫外–可见光光电[子]发射体uv-visible spectral response 紫外–可见光光谱响应uvicon 紫外二次电子导电管uviol 透紫外[线]玻璃uviol glass 透紫外线玻璃uvioresistant 不透紫外线的uxmeter 勒克司计，照度计光电英语词汇(U) 相关内容:。

EPOCH-II高流量输出单元I说明书

EPOCH-II ®High-Current Output UnitI 1000 VA of high current I Rugged, portable test setIUp to 187 Amperes maximum outputEPOCH-IIHigh-Current Output UnitDESCRIPTIONThe EPOCH-II ®is a high-current output unit designed to be controlled by the PULSAR ®in combination with the High-Current Interface Module to produce a rugged,portable high-current, high-volt/ampere test set. The EPOCH-II also is designed to be controlled by the EPOCH-10®Relay T est Set.PULSAR/EPOCH-II or EPOCH-10/EPOCH-II combination uses microprocessor-based, digitally synthesized sine wave generators and solid-state regulated power amplifiers to provide sinusoidal voltage and current outputs with precise control of the phase-angle relationships.These combinations will produce accurate test results even with a fluctuating power source or when testing nonlinear or highly saturable relays.An optional IEEE-488 GPIB interface transforms the EPOCH-10/EPOCH-II combination into a programmable automatic test system when used with an externalcontroller or computer. Amplitude and/or phase angle can be set to desired values, step changed, ramped, or pulsed to new values.APPLICATIONSPULSAR/EPOCH-II or EPOCH-10/EPOCH-II combination is designed to test both complex protective relays which require phase-shifting capability and simpler relays,including all overcurrent relays.The table above lists the different types of relays by device numbers, and the different combinations of a PULSAR or EPOCH-10s and an EPOCH-II required to test them.FEATURES AND BENEFITSI Output current source has a 5-minute duty cycle rating of 1000 volt-amperes.IFour output ranges at 0.01 ampere and two output ranges at 0.1 ampere are provided.IT ough steel, sealed enclosure provides a high shock and vibration resistance.ICompletely compatible with PULSAR via the High-Current Interface Module and the EPOCH-10 units.Device No.Relay TypesSpecifyOne EPOCH-II and PULSAR with High-Current Interface Module or one EPOCH-10One EPOCH-II and PULSAR with Interface Module or two EPOCH-10sInstantaneous Overcurrent up to 187 A at 1000 VADirectional Overcurrent up to 187 A at 1000 VA All of the above plus. . .Differential Distance (open-delta)50678721One EPOCH-II and PULSAR with Interface Modules or three EPOCH-10sDistance (wye)21Ground DirectionalOvercurrent up to 187 A at 1000 VA67NOvercurrent up to 187 A at 1000 VA 51 1981EPOCH-II High-Current Output UnitSPECIFICATIONSInputInput Voltage (specify one)115 V ±10%, 50/60 Hz, 30 A (at full rated output)OR230 V ±10%, 50/60 Hz, 20 AOutputOutput CurrentT o provide a variety of test circuit impedances, six output taps with two ranges are provided.High Range2.00 to 10.00 A at 100 V max3.00 to 15.00 A at 66.6 V max8.00 to 40.00 A at 25 V max10.00 to 50.00 A at 20 V max20.00 to 100.0 A at 10 V max34.00 to 170.0 A at 5.9 V maxOutput Power:1000 VALow Range2.00 to 10.00 A at 50 V max3.00 to 1 5.00 A at 33.3 V max8.00 to 40.00 A at 12.5 V max10.00 to 50.00 A at 10 V max20.00 to 100.0 A at 5 V max34.00 to 170.0 A at 2.95 V maxOutput Power:500 VAAccuracyT ypical:±0.5% of settingMaximum:±1.0% of settingAlarm will indicate when amplitude, phase angle, or waveform is in error.ResolutionFour ranges:0.01 AT wo ranges:0.l ADuty CycleFive minutes at full rated VA output. Fifteen minutes recovery time.Overrange CapabilityThe EPOCH-II has an overrange capability of +10% for each tap with a maximum output current of 187 A on the 170 A tap. DistortionLess than 1% typical, 3% max.Output of EPOCH-10/EPOCH-II CombinationFrequencyI Synchronized to input power sourceI60 Hz crystal-controlledI50 Hz crystal-controlled AccuracyI Synchronized, tracks input frequencyI±0.006 Hz for 60-Hz crystal control (±001%)I±0.005 Hz for 50-Hz crystal control (±0.01%)Output of PULSAR and Interface Module Connected to EPOCH-II The High-Current Interface Module provides a variable frequency signal to the Epoch-II High-Current Output Unit.Output frequency is continuously displayed for each channel with large, high-intensity LEDs with the following ranges:5.000 to 99.999 Hz100.01 to 999.99 HzFrequency Accuracy:±10 ppm at 23°C, ±2°C)Current Phase Angle ControlAngle is adjusted on the EPOCH-10 control unit by 4-digit, pushbutton control with large LED display of setting.Range:0.0 to 359.9°Resolution:0.1°Accuracy:less than ±0.3°typical, ±1.0°maxControl SectionThe control unit for the EPOCH-II high-current section is PULSAR (with the High-Current Interface Module), an EPOCH-I or EPOCH-10. Thus, the excellent operating and control features of PULSAR and the EPOCH-10 are used to control the EPOCH-II.Note:When the EPOCH-II is in use, the current output of the EPOCH-10 control unit is inoperative. All EPOCH-10s can control an EPOCH-II high-current section. When the high-current section of the EPOCH-II is not needed, the EPOCH-10 can be used independently or slaved together with other EPOCH units. ProtectionThe input line circuit is breaker-protected. The dc power supply is overcurrent-protected. In addition, overvoltage protection is provided on the input line circuit.The power amplifiers are forced-air cooled and are protected by thermal-overload sensors.Audio and visual alarms on the PULSAR and EPOCH-10 control units indicate whenever the current or potential outputs are overloaded.TemperatureOperating32 to 122°F (0 to 50°C)Reduced duty cycle above 113°F (45°C)Storage–13 to +158°F (–25°to +70°C)Dimensions7.6 H x 19.75 W x 21.6 D in.(193 H x 502 W x 549 D mm)Weight115 lb (52.3 kg)EPOCH-II with EPOCH-10 control unitEPOCH-II High-Current Output UnitUKArchcliffe Road Dover CT17 9EN EnglandT +44 (0) 1304 502101 F +44 (0) 1304 207342UNITED STATES4271 Bronze Way DallasTX75237-1017 USAT 800 723 2861 (USA only)T +1 214 330 3203F +1 214 337 3038OTHER TECHNICAL SALES OFFICESValley Forge USA, Toronto CANADA,Mumbai INDIA, Trappes FRANCE,Sydney AUSTRALIA, Madrid SPAINand the Kingdom of BAHRAIN.Registered to ISO 9001:2000 Reg no. Q 09290Registered to ISO 14001 Reg no. EMS 61597EPOCH_II_DS_en_V10The word ‘Megger’ is a registeredtrademark。

HOLOEYE - LCOS空间光调制器技术

Simulation of the dynamic response for optimized design
Driving schemes: PCM
Example of pixel voltage using PCM (field inversion omitted)
— ASIC or FPGA-driven — High bandwidth (140-266MHz) — Microdisplay data bus 32-128
—Pixel arrays up to 4160x2464 (10Mpix)
Image courtesy Fraunhofer IZM/Gollhardt
RCWA 2D simulation, light wave (Hx) reflected from the backplane, two different interpixel gaps
— Phase shift > 1 wavelength (>2pi)
Simulation of director distribution (2D) and electrostatic field for 4 pixel blazed grating
Simulation of director distribution (2D) for 8 pixel binary grating
Courtesy University of Potsdam
Driving schemes for LCOS SLMs
— Analogue modulation is theoretically ideal — Pulse-width modulation is poor for phase applications — Pulse code modulation with high-bandwidth and custom sequences was adapted

与激光有关的英文文献

与激光有关的英文文献Revised at 16:25 am on June 10, 2019L a s e r t e c h n o l o g y R. E. Slusher Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974 Laser technology during the 20th century is reviewed emphasizing the laser’s evolution from science to technology and subsequent contributions of laser technology to science. As the century draws to a close, lasers are making strong contributions to communications, materials processing, data storage, image recording, medicine, and defense. Examples from these areas demonstrate the stunning impact of laser light on our society. Laser advances are helping to generate new science as illustrated by several examples in physics and biology. Free-electron lasers used for materials processing and laser accelerators are described as developing laser technologies for the next century.S0034-68619902802-01. INTRODUCTIONLight has always played a central role in the study of physics, chemistry, and biology. Light is key to both the evolution of the universe and to the evolution of life on earth. This century a new form of light, laser light, has been discovered on our small planet and is already facilitating a global information transformation as well as providing important contributions to medicine, industrial material processing, data storage, printing, and defense. This review will trace the developments in science and technology that led to the invention of the laser and give a few examples of how lasers are contributing to both technological applications and progress in basic science. There are many other excellent sources that cover various aspects of the lasers and laser technology including articles from the 25th anniversary of the laser Ausubell and Langford, 1987 and textbooks ., Siegman, 1986; Agrawal and Dutta, 1993; and Ready, 1997.Light amplification by stimulated emission of radiation LASER is achieved by exciting the electronic, vibrational, rotational, or cooperative modes of a material into a nonequilibrium state so that photons propagating through the system are amplified coherently by stimulated emission. Excitation of this optical gain medium can be accomplished by using optical radiation, electrical current and discharges, or chemical reactions. The amplifying medium is placed in an optical resonator structure, for example between two high reflectivity mirrors in a Fabry-Perot interferometer configuration. When the gain in photon number for an optical mode of the cavity resonator exceeds the cavity loss, as well as loss from nonradiative and absorption processes, the coherent state amplitude of the mode increases to a levelwhere the mean photon number in the mode is larger than one. At pump levels above this threshold condition,the system is lasing and stimulated emission dominates spontaneous emission. A laser beam is typically coupled out of the resonator by a partially transmitting mirror. The wonderfully useful properties of laser radiation include spatial coherence, narrow spectral emission, high power, and well-defined spatial modes so that the beam can be focused to a diffraction-limited spot size in order to achieve very high intensity. The high efficiency of laser light generation is important in many applications that require low power input and a minimum of heat generation.When a coherent state laser beam is detected using photon-counting techniques, the photon count distribution in time is Poissonian. For example, an audio output from a high efficiency photomultiplier detecting a laser field sounds like rain in a steady downpour. This laser noise can be modified in special cases, ., by constant current pumping of a diode laser toobtain a squeezed number state where the detected photons sound more like a machine gun than rain. An optical amplifier is achieved if the gain medium is not in a resonant cavity. Optical amplifiers can achievevery high gain and low noise. In fact they presently have noise figures within a few dB of the 3 dB quantum noise limit for a phase-insensitive linear amplifier, ., they add little more than a factor of two to the noise power of an input signal. Optical parametric amplifiers OPAs, where signal gain is achieved by nonlinear coupling of a pump field with signal modes, can be configured to add less than 3 dB of noise to an input signal. In an OPA the noise added to the input signal can be dominated by pump noise and the noise contributed by a laser pump beam can be negligibly small compared to the large amplitude of the pump field.2. HISTORYEinstein 1917 provided the first essential idea for the laser, stimulated emission. Why wasn’t the laser invented earlier in the century Much of the early work on stimulated emission concentrates on systems near equilibrium, and the laser is a highly nonequilibrium system. In retrospect the laser could easily have been conceived and demonstrated using a gas discharge during the period of intense spectroscopic studies from 1925 to 1940. However, it took the microwave technology developed during World War II to create the atmosphere for thelaser concept. Charles Townes and his group at Columbia conceived the maser microwave amplification by stimulated emission of radiation idea, based on their background in microwave technology and their interest in high-resolution microwave spectroscopy. Similar maser ideas evolved in Moscow Basov and Prokhorov, 1954 and at the University of Maryland Weber, 1953. The first experimentally demonstrated maser at Columbia University Gordon et al., 1954, 1955 was based on an ammonia molecular beam. Bloembergen’s ideas for gain in three level systems resulted in the first practical maser amplifiers in the ruby system. These devices have noise figures very close to the quantum limit and were used by Penzias and Wilson in the discovery of the cosmic background radiation.Townes was confident that the maser concept could be extended to the optical region Townes, 1995. The laser idea was born Schawlow and Townes, 1958 when he discussed the idea with Arthur Schawlow, who understood that the resonator modes of a Fabry-Perot interferometer could reduce the number of modes interacting with the gain material in order to achieve high gain for an individual mode. The first laser was demonstrated in a flash lamp pumped ruby crystal by Ted Maiman at Hughes Research Laboratories Maiman, 1960. Shortly after the demonstration of pulsed crystal lasers, a continuouswave CW He:Ne gas discharge laser was demonstrated at Bell Laboratories Javan et al., 1961, first at mm and later at the red nm wavelength lasing transition. An excellent article on the birth of the laser is published in a special issue of Physics Today Bromberg, 1988.The maser and laser initiated the field of quantum electronics that spans the disciplines of physics and electrical engineering. For physicists who thought primarilyin terms of photons, some laser concepts were difficult to understand without the coherent wave concepts familiar in the electrical engineering community. For example, the laser linewidth can be much narrower than the limit that one might think to be imposed by the laser transition spontaneous lifetime. Charles Townes won a bottle of scotch over this point from a colleague at Columbia. The laser and maser also beautifully demonstrate the interchange of ideas and impetus between industry, government, and university research.Initially, during the period from 1961 to 1975 there were few applications for the laser. It was a solution looking for a problem. Since the mid-1970s there has been an explosive growth of laser technology for industrial applications. As a result of this technology growth, a new generation of lasers including semiconductor diode lasers, dye lasers, ultrafast mode-locked Ti:sapphire lasers, optical parameter oscillators, and parametric amplifiers is presently facilitating new research breakthroughs in physics, chemistry, and biology.3. LASERS AT THE TURN OF THE CENTURYSchawlow’s ‘‘law’’ states that everything lases if pumped hard enough. Indeed thousands of materials have been demonstrated as lasers and optical amplifiers resulting in a large range of laser sizes, wavelengths, pulse lengths, and powers. Laser wavelengths range from the far infrared to the x-ray region. Laser light pulses as short as a few femtoseconds are available for research on materials dynamics. Peak powers in the petawatt range are now being achieved by amplification of femtosecond pulses. When these power levels are focused into a diffraction-limited spot, the intensities approach 1023 W/cm2. Electrons in these intense fields are accelerated into the relativistic range during a single optical cycle, and interesting quantum electrodynamic effects can be studied. The physics of ultrashort laser pulses is reviewed is this centennial series Bloembergen, 1999.A recent example of a large, powerful laser is the chemical laser based on an iodine transition at a wavelength of mm that is envisioned as a defensive weapon Forden, 1997. It could be mounted in a Boeing 747 aircraft and would produce average powers of 3 megawatts, equivalent to 30 acetylene torches. New advances in high quality dielectric mirrors and deformable mirrors allow this intense beam to be focused reliably on a small missile carrying biological or chemical agents and destroy it from distances of up to 100 km. This ‘‘star wars’’ attack can be accomplished during the launch phase of the target missile so that portions of the destroyed missile would fall back on its launcher, quite a good deterrent for these evil weapons. Captain Kirk and the starship Enterprise may be using this one on the Klingons At the opposite end of the laser size range are microlasers so small that only a few optical modes are contained in a resonator with a volume in the femtoliter range. These resonators can take the form of rings or disks only a few microns in diameter that use total internal reflection instead of conventional dielectric stack mirrors in order to obtain high reflectivity. Fabry-Perot cavities only a fraction of a micron in length are used for VCSELs vertical cavity surface emitting lasers that generate high quality optical beams that can be efficiently coupled to optical fibers Choquette and Hou, 1997. VCSELs may find widespread application in optical data links.4. MATERIALS PROCESSING AND LITHOGRAPHYHigh power CO2 and Nd:YAG lasers are used for a wide variety of engraving, cutting, welding, soldering, and 3D prototyping applications. rf-excited, sealed off CO2 lasers are commercially available that have output powers in the 10 to 600 W range and have lifetimes of over 10 000 hours. Laser cutting applications include sailclothes, parachutes, textiles, airbags, and lace. The cutting is very quick, accurate, there is no edge discoloration, and a clean fused edge is obtained that eliminatesfraying of the material. Complex designs are engraved in wood, glass, acrylic, rubber stamps, printing plates, plexiglass, signs, gaskets, and paper. Threedimensional models are quickly made from plastic or wood using a CAD computer-aided design computer file.Fiber lasers Rossi, 1997 are a recent addition to the materials processing field. The first fiber lasers were demonstrated at Bell Laboratories using crystal fibers in an effort to develop lasers for undersea lightwave communications. Doped fused silica fiber lasers were soon developed. During the late 1980s researchers at Polaroid Corp. and at the University of Southampton invented cladding-pumped fiber lasers. The glass surrounding the guiding core in these lasers serves both to guide the light in the single mode core and as a multimode conduit for pump light whose propagation is confined to the inner cladding by a low-refractive index outer polymer cladding. Typical operation schemes at present use a multimode 20 W diode laser bar that couples efficiently into the large diameter inner cladding region and is absorbed by the doped core region over its entire length typically 50 m. The dopants in the core of the fiber that provide the gain can be erbium for the mm wavelength region or ytterbium for the mm region. High quality cavity mirrors are deposited directly on the ends of the fiber. These fiber lasers are extremely efficient, with overall efficiencies as high as 60%. The beam quality and delivery efficiency is excellent since the output is formed as the single mode output of the fiber. These lasers now have output powers in the 10 to 40 W range and lifetimes of nearly 5000 hours. Current applications of these lasers include annealing micromechanical components, cutting of 25 to 50 mm thick stainless steel parts, selective soldering and welding of intricate mechanical parts, marking plastic and metal components, and printing applications.Excimer lasers are beginning to play a key role in photolithography used to fabricate VLSI very large scale integrated circuit chips. As the IC integrated circuit design rules decrease from mm 1995 to mm 2002, the wavelength of the light source used for photolithographic patterning must correspondingly decrease from 400 nm to below 200 nm. During the early 1990s mercury arc radiation produced enough power at sufficiently short wavelengths of 436 nm and 365 nm for high production rates of IC devices patterned to mm and mm design rules respectively. As the century closes excimer laser sources with average output powers in the 200 W range are replacing the mercury arcs. The excimer laser linewidths are broad enough to prevent speckle pattern formation, yet narrow enough, less than 2 nm wavelength width, to avoid major problems with dispersion in optical imaging. The krypton fluoride KF excimer laser radiation at 248 nm wavelength supports mm design rules and the ArF laser transition at 193nm will probably be used beginning with mm design rules. At even smaller design rules, down to mm by 2008, the F2 excimer laser wavelength at 157 nm is a possible candidate, although there are no photoresists developed for this wavelength at present. Higher harmonics of solid-state lasers are also possibilities as high power UV sources. At even shorter wavelengths it is very difficult for optical elements and photoresists to meet the requirementsin the lithographic systems. Electron beams, x-rays and synchrotron radiation are still being considered for the 70 nm design rules anticipated for 2010 and beyond.5. LASERS IN PHYSICSLaser technology has stimulated a renaissance in spectroscopies throughout the electromagnetic spectrum. The narrow laser linewidth, large powers, short pulses, and broad range of wavelengths has allowed new dynamic and spectral studies of gases, plasmas, glasses, crystals, and liquids. For example, Raman scattering studies of phonons, magnons, plasmons, rotons, and excitations in 2D electron gases have flourished since the invention of the laser. Nonlinear laser spectroscopies have resulted in great increases in precision measurement as described in an article in this volume Ha¨nsch and Walther 1999.Frequency-stabilized dye lasers and diode lasers precisely tuned to atomic transitions have resulted in ultracold atoms and Bose-Einstein condensates, also described in this volume Wieman et al., 1999. Atomicstate control and measurements of atomic parity nonconservation have reached a precision that allows tests of the standard model in particle physics as well as crucial searches for new physics beyond the standard model. In recent parity nonconservation experiments Wood et al., 1997 Ce atoms are prepared in specific electronic states as they pass through two red diode laser beams. These prepared atoms then enter an optical cavity resonator where the atoms are excited to a higher energy level by high-intensity green light injected into the cavity from a frequency-stabilized dye laser. Applied electric and magnetic fields in this excitation region can be reversed to create a mirrored environment for the atoms. After the atom exits the excitation region, the atom excitation rate is measured by a third red diode laser. Very small changes in this excitation rate with a mirroring of the applied electric and magnetic fields indicate parity nonconservation. The accuracy of the parity nonconservation measurement has evolved over several decades to a level of %. This measurement accuracy corresponds to the first definitive isolation of nuclear-spin-dependent atomic parity violation.。

(完整版)超快光学第01章入门

Mode-locking and mode-locking techniispersion (GVD)
Compensating GVD with a pulse compressor
Continuum generation
Measuring ultrashort pulses
Second-harmonic-generation of infrared light yields this beautiful
display of intense green light.
Continuum generation
Continuum Generation: focusing a femtosecond pulse into a clear medium turns the pulse white.
Laser power
A generic ultrashort-pulse laser
A generic ultrafast laser has a broadband gain medium, a pulseshortening device, and two or more mirrors:
Pulse-shortening devices include: Saturable absorbers Phase modulators Dispersion compensators Optical-Kerr media
Irradiance vs. time
Spectrum
Long pulse
time Short pulse
frequency
time
frequency
Ultrafast laser media

FemtosecondZ-scanMeasurement：飞秒激光Z扫描测量

Off-Resonant Third-Order Optical Nonlinearity of Au Nanoparticle Array byFemtosecond Z-scan Measurement*WANG Kai(王凯)1,LONG Hua(龙华)1,FU Ming(付明)1,YANG Guang(杨光)1**,LU Pei-Xiang(陆培祥)1,2** 1Wuhan National Laboratory for Optoelectronics,Huazhong University of Science and Technology,Wuhan430074 2School of Science,Wuhan Institute of Technology,Wuhan430073(Received21January2010)A periodic triangular-shaped Au nanoparticle array is fabricated on a quartz substrate using nanosphere lithogra-phy and pulsed laser deposition,and the linear and nonlinear optical properties of metal particles are studied.The morphology of the polystyrene nanosphere mask(D=820nm)and the Au nanoparticle array are investigated by scanning electron microscopy.The surface plasmon resonance absorption peak is observed at606nm,which is in good agreement with the calculated result using the discrete dipole approximation method.By performing the Z-scan method with femtosecond laser(800nm,50fs),the optical nonlinearities of Au nanoparticle array are determined.The results show that the Au particles exhibit negative nonlinear absorption and positive nonlinearrefractive index with the effective third-order optical nonlinear susceptibilityχ(3)eff can be up to(8.8±1.0)×10−10esu under non-resonant femtosecond laser excitation.PACS:42.70.Mp,81.16.Nd DOI:10.1088/0256-307X/27/12/124204Noble metal nanoparticles such as Au,Ag and Cu have been of particular interest for a long time because of their unique optical properties called sur-face plasmon resonance(SPR),which is caused by the collective resonance of the conductive electrons in re-sponse to incident light and is widely used in applica-tions such as catalysis,biological sensors and molecu-lar rulers.[1−3]Recently,many studies have focused on the nonlinear properties of noble metal nanoparticles due to their large nonlinear optical effects and fast re-sponse time,which have great potential applications for all-optical switching and computing.[4−7] It is well known that the optical nonlinearities of noble metal nanoparticles can be greatly enhanced at the SPR position and strongly dependent on the nanoparticles’size,shape and distribution.However, among most of the previous works,the metal particles are comprised of spheres of various sizes or random distributed,which leads to broad SPR spectra and weak optical enhancement.The nanosphere lithogra-phy(NSL)has been proved to be a powerful tool de-veloped from natural lithography by Van Duyne[8,9]in 1995,to fabricate periodic particle array(PPA)with tunable shape,size and height,which make it possi-ble to quantitatively study the optical properties of nanoparticles.Recently,several studies on the nonlinear opti-cal properties of metal nanoparticle array have been reported.Both theoretical[10,11]and experimental studies[12,13]indicate that anisotropy of the shape and geometric distribution of the metal nanoparticles could enhance greatly the optical nonlinearityχ(3). However,up to now,the measurement of the nonlin-ear optical properties of the Au periodic nanoparticle array excited by ultrafast laser(50fs)at a wavelength of800nm has seldom been reported.In this Letter,we study the optical nonlinearities of an Au nanoparticle array determined by femtosecond laser.The morphology of the Au nanoparticle array is observed by scanning electron microscopy(SEM). The third-order nonlinear property is measured by Z-scan method,which is a useful tool to measure the nonlinear optical properties such as nonlinear absorp-tion and refraction.[14]The real and imaginary parts of the third-order nonlinear susceptibility,Reχ(3)and Imχ(3),are determined by performing open-aperture (OA)and closed-aperture(CA)Z-scan measurements, respectively.In the NSL processing step,the monodisperse polystyrene(PS)nanosphere suspensions were pur-chased from Duke Scientific Corp.,and the diame-ter of the spheres used in the experiment was820±5nm.The details of the NSL have been described elsewhere.[15]For the PLD processing step,a KrF (Lambda Physik,248nm)laser beam was used as the laser source with the laser energy density of about 2J/cm2focused on the target and the laser repetition frequency was6Hz.The deposition time was set to be 30min.The surface morphology of the NSL mask and the Au PPAs was observed by SEM(FEI QUANTA 200).The SPR spectra were measured by UV-visible absorption spectroscopy(U-3310UV Solutions)in a wavelength range from340nm to900nm.The inci-dent light was perpendicular to the samples through a small aperture with diameter of2mm to measure the absorption properties of small area.In order to*Supported by the National Natural Science Foundation of China under Grant No10974062,the National Science Fund for Distinguished Young Scholars under Grant No60925021,and the National Basic Research Program of China under Grant No 2010CB923203.**Email:***************;********************c○2010Chinese Physical Society and IOP Publishing Ltdcompare with the experimental result,the theoretical calculations based on the discrete dipole approxima-tion (DDA)method were also performed.The third-order nonlinear optical properties of the sample were determined by the Z-scan method.In our experiments,a femtosecond laser system,which consisted of a mode-locked Ti:sapphire oscil-lator and a regenerative amplifier (Spitfire,Spectra-Physics,800nm,50fs,1kHz),was used as the light source.The sample was scanned along the optical axis (z -direction)and focused by a lens with a focal length of 200mm.When there is no aperture in front of the detector,OA Z-scan curves are obtained and the nonlinear absorption coefficient βcan be deter-mined,while the nonlinear refractive index γis deter-mined by CA Z-scan curves using a small aperture.The radius of the beam waist ω0was 33µm,which iscalculated from the equation ω(z )2=ω02(1+z 2/z 20),where z 0=πω20/λis the Rayleigh length.The value of z 0was calculated to be 4.2mm,much larger than the thickness of either the 0.2-mm substrate or the sam-ple.The transmitted beam energy through OA or CA is received by silicon diodes (PC20-6,Silicon Sensor GmbH)and double-phase lock-in amplifier (SR830,Stanford ResearchSystem).nmFig.1.SEM image of large area (20×15µm 2)of a well-packed nanosphere mask with diameter D =820nm.The inset shows the SEM image of the details of the nanosphere mask.a =190 nm5 m m Fig.2.The SEM image of large area (25×20µm 2)of anAu nanoparticle array.The inset shows the cell of trian-gular Au nanoparticle array.Figure 1shows the SEM image (20×15µm 2)of the polystyrene nanosphere mask.It can be seen that most of the area is occupied by well-packednanospheres.The inset in Fig.1shows the details of the mask that the triangular-shaped gaps between nanospheres can only allow the deposited source to go through.Figure 2shows the SEM image of the Au nanoparticles at a scale of 25×20µm 2and the Au PPAs can be observed clearly.The inset in Fig.2shows clearly the shape and the size of the Au triangu-lar prism.The size of the nanoparticle can be defined with two parameters:the in-plane perpendicular bi-sector a and the out-of-plane particle height b .By a geometrical calculation,D =0.233a ,the value of a is calculated to be 190nm,which is in good agreement with the experimental results shown in the inset in Fig.2.Fig.3.Absorption spectrum of Au nanoparticle array with SPR peak at 606nm.The dotted line shows the DDA calculation result of absorption properties for a sin-gle Au particle with the same cross section,and a particle height of 16nm.The dashed line shows the average DDA results of three Au particles with the same cross section and different height:14nm,16nm and 18nm.The linear absorption of the Au PPAs was mea-sured in the wavelength range from 340nm to 900nm and the black line shows the absorption spectrum in Fig.3.It can be seen that the absorption peak due to SPR of Au particles is found to be located at 606nm.With the Mie theory,when εr (λ)+2εd =0and εi (λ)is small,the SPR condition occurs.Here εd is the dielectric constant of the medium surround-ing the metal nanoparticle,εr (λ)and εi (λ)are the real and the imaginary parts of dielectric function of the metal particles.The optical enhancement un-der laser excitation near the SPR position is much stronger than that in the off-resonant position such as λ=800nm.In comparison,the optical proper-ties of Au particles with the same cross section and particle height of 14nm,16nm and 18nm were calcu-lated using the DDA method.[16,17]The dotted line shows the absorption spectrum for a single 16-nm-height particle.It can be seen that the position of the SPR peak is located at 606nm,which is the same as the experimental results.The dashed line shows the average DDA results of three Au particles with differ-ent heights 14nm,16nm and 18nm.The deviationof the Au particles shape and height from theoretical values leads to the SPR peaks shifting and a broader SPR spectrum.Thus it is reasonable that the particle height is estimated to be16±2nm.Fig.4.Z-scan measurements at I0=59.5GW/cm2.(a) Open-aperture Z-scan results of Au nanoparticle array,the solid line indicates the theoretical fit.(b)Closed-aperture Z-scan result of Au nanoparticle array,the solid line indi-cates the theoretical fit.Figure4shows the typical OA and CA Z-scan results for the Au PPAs.The black dots indicate the experimental data and the solid curve represents the theoretical fit.The laser pulse energy at the fo-cal spot,E0,was100nJ and the laser intensity at the focal point,I0=E0/πω2τ,was calculated to be 59.5GW/cm2.Under the repetition rate of1kHz,the accumulative thermal effects can be neglected.The transmitted energy at each position was measured16 times to obtain a reliable average value.One can see that the curve in Fig.4(a)comprises a normalized peak,indicating the presence of saturation of absorp-tion(SA)in the Au PPAs.Under these conditions, as the shape of the Z-scan results for the substrate is flat,the substrates have a very small nonlinear opti-cal effect that can be neglected and the large nonlinear absorption observed here results from the Au PPAs.Figure4(b)shows the CA Z-scan data for Au PPAs.In order to obtain nonlinear refraction infor-mation,an approximate method was used where the closed-aperture transmittance was divided by the cor-responding open-aperture data.It can be seen that the shape of the curve exhibits a positive value for the nonlinear refractive index.From Fig.4(b),one can find that the distance between the peak and the val-ley(∆Z p−v)is about7.6mm as compared to1.71z0, which indicates that the observed nonlinear effect is the third-order response.The difference between nor-malized transmittances at peak and valley∆T p−v is 0.04,and S=0.18is the transmittance of the small aperture.The nonlinear absorption coefficientβ(m/W)and the nonlinear optical refractive index(m2/W)can be calculated using the method described in detail elsewhere.[14]The values ofβandγof Au PPAs were calculated to be(−1.3±0.1)×10−8m/W and (1.3±0.2)×10−15m2/W,respectively.The real and imaginary parts ofχ(3)of the Au PPAs can be ob-tained by the equations Reχ(3)(esu)=cn20γ/120π2 and Imχ(3)(esu)=cn20β/240π2k,where k=2π/λis the wave vector.The values of Reχ(3)and Imχ(3)were calculated to be(7.4±1.0)×10−10esu and(−4.7±0.4)×10−10esu,respectively.The absolute value of χ(3)was obtained to be about(8.8±1.0)×10−10esu, indicating the large third-order nonlinear optical prop-erties in Au PPAs using the femtosecond laser excita-tion.Fig.5.(a)Open-aperture Z-scan results of Au nanoparti-cle array in different exciting energy.(b)Intensity depen-dence of the nonlinear absorption coefficientβ(m/W).Figure5(a)shows the OA Z-scan results for Au PPAs at different excitation energies.With the increasing laser intensity at the focal point I0=29.5GW/cm2,46.4GW/cm2,59.5GW/cm2, 89.3GW/cm2and178GW/cm2,the normalized transmittance peak becomes progressively larger and exhibits SA process.The excited intensity induces ground-state plasmon to be bleached,which leads to the increasing OA transmittance with the increasing excited intensity.Figure5(b)shows the laser inten-sity dependence of values ofβthat are independent of the laser intensity when the intensity is relatively low (<60GW/cm2)and starts to decrease when the laser energy is higher.The high(>60GW/cm2)inten-sity results in the free carrier absorption dominating the region and the transmittance decreases with the increasing intensity and the reverse saturation of ab-sorption(RSA)process becomes considerable.In the ultrashort pulse temporal regime(smaller than a few picoseconds),the contribution of the hot electron phenomenon toχ(3)m is expected to be significant.[15]Hereχ(3)m and the corresponding sus-ceptibility response to the local field E loc,χ(3)eff,are related by[18]χ(3)eff=pf2|f|2χ(3)m,(1) where p is the metal volume fraction and f the ratio between the local field E loc and the applied field E0.E loc=3εdεm+2εdE0.(2) In the large particle limit,it is appropriate to calcu-late theεm value from the data for bulk Au.[19]Here εd=1is the dielectric constant of the host material for air matrices.The value of local-field factor|f|is estimated to be0.15at the wavelength of800nm for spherical particles using Eq.(2).However,in the case of triangular-shaped nanoparticle arrays,the local-field factor f cannot be calculated using Eq.(2).Using the following equation,the value of local-field factor can be estimated,[20]α=pωn0c|f|2ε′′m,(3)whereα0=8.5×103cm−1is the linear absorption coefficient at the wavelength of800nm,ωis the an-gular frequency of the incident light,c is the velocity of light.For the nanoparticle array in this experi-ment,p=0.08,which is a very low value of volume fraction of metal nanoparticles.The value of local-field factor|f|is estimated to be1.6,which is about 11times larger than that for the spherical particles. Thus the enhancement observed in Au PPA is prob-ably due to the stronger local field in the triangular-shaped nanoparticles.For comparison,the nonlinear coefficients of sev-eral thin films in the near infrared region under the ex-citation of femtosecond laser pulses are listed in Table 1.It is suggested that the Au nanoparticle array ex-hibits large optical nonlinear coefficients and has great potential applications in nonlinear photonics devices.Table1.Femtosecond optical nonlinearities of several films/particles in the near infrared region.Films/Particlesλ(nm)I0(GW/cm2)Pulse width(fs)β(m/W)γ(m2/W) Au PPAs80059.550−1.3×10−81.3×10−15DWNT a[21]800 1.5501.4×10−10−2.6×10−15BiFeO3[22]7801563501.6×10−101.5×10−17LGF b[23]8000.51503×10−82×10−17VO2[24]80016.91202.7×10−9−7.1×10−16a Double walled carbon nanotubes(DWNT).b lead-germanium based films(LGF).In summary,a triangular-shaped Au nanoparticle array has been fabricated by NSL and the PLD tech-nique.The nonlinear optical properties of the sample are investigated by the Z-scan method at a wavelength of800nm with pulse duration of50fs.The third-order nonlinear optical susceptibility is determined to be(8.8±1.0)×10−10esu.The large third-order non-linearity shows that Au nanoparticle arrays have great potential applications in ultrafast nonlinear photonic devices such as all-optical switching and computing. References[1]Haes J,Hall W P,Chang L,Klein W L and Van Duyne RP2004Nano Lett.41029[2]Park S J,Taton T A and Mirkin C A2002Science2951503[3]Narayanan R and El-Sayed M A2004Nano Lett.41343[4]Okada N,Hamanaka Y,Nakamura A,Pastoriza-Santos Iand Liz-Marzán L M2004J.Phys.Chem.B1088751 [5]Hamanaka Y,Nakamura A,Hayashi N and Omi S2003J.Opt.Soc.Am.B201227[6]Jayabalan J,Singh A,Chari R and Oak S M2007Nan-otechnology18315704[7]Tran P1997J.Opt.Soc.Am.B142589[8]Hulteen J C and Van Duyne R P1995J.Vac.Sci.Technol.A131553[9]Haynes C L and Van Duyne R P2001J.Phys.Chem.B1055599[10]Yuen K P,Law M F and Sheng P1997Phys.Rev.E56R1322[11]Huang J P and Yu K W2005J.Opt.Soc.Am.B221640[12]Shen H,Cheng B,Lu G W,Ning T Y,Guan D Y,Zhou YL and Chen Z G2006Nanotechnology174274[13]Nahata A,Linke R A and Ohashi K2003Opt.Lett.28423[14]Sheik-Bahae M,Said A A,Wei T H,Hagan D J and VanStryland E W1990IEEE J.Quantum Electron.26760 [15]Huang W Y,Qian W and El-Sayed M A2005J.Phys.Chem.B10918881[16]Draine B T and Flatau P J1994J.Opt.Soc.Am.A1114919[17]Draine B T and Flatau P J2008User Guide to theDiscrete Dipole Approximation Code DDSCAT7.0 arXiv:0809.0337v5[18]Ricard D,Roussignol P and Flytzanis C1985Opt.Lett.10511[19]Lide D R2001Handbook of Chemistry and Physics(Florida:CRC)[20]Uchida O K,Kaneko S,Omi S,Hata C,Tanji H,AsaharaY,Ikushima A J,Tokizaki T and Nakamura A1994J.Opt.Soc.Am.B111236[21]Kamaraju N,Kumar S,.Karthikeyan B,Moravsky A,Loutfy R O and Sood A K2008Appl.Phys.Lett.93 091903[22]Gu B,Wang Y,Wang J and Ji W2009Opt.Express1710970[23]Rativa D,Araujo R E,Araújo C B,Gomes A S L andKassab L R P2007Appl.Phys.Lett.90231906[24]Lopez R,Haglund R F,Feldman L C,Boatner L A andHaynes T E2004Appl.Phys.Lett.855191。

OPTICS EXPRESS

Long lifetime plasma channel in air generated by multiple femtosecond laser pulses and anexternal electrical fieldJiabin Zhu, Zhonggang Ji, Yunpei Deng, Jiansheng Liu, Ruxin Li, and Zhizhan Xu State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics (SIOM), ChineseAcademy of Sciences, Shanghai 201800, Chinajiabinzhu@Abstract: The lifetime of a plasma channel produced by self-guidingintense femtosecond laser pulses in air is largely prolonged by adding a highvoltage electrical field in the plasma and by introducing a series offemtosecond laser pulses. An optimal lifetime value is realized throughadjusting the delay among these laser pulses. The lifetime of a plasmachannel is greatly enhanced to 350 ns by using four sequential intense100fs(FWHM) laser pulses with an external electrical field of about350kV/m, which proves the feasibility of prolonging the lifetime of plasmaby adding an external electrical field and employing multiple laser pulses.© 2006 Optical Society of AmericaOCIS codes: (320.7120) ultrafast phenomena; (350.5400) plasmasReferences and links1. A. Braun, G. Korn, X. Liu, D. Du, J. Squier, and G. Mourou, “Self-channeling of high-peak-powerfemtosecond laser pulses in air,” Opt. Lett. 20, 73-75 (1995).2. E. T. J. Nibbering, P. F. Curley, G. Grillon, B. S. Prade, M. A. Franco, F. Salin, and A. Mysyrowicz,“Conical emission from self-guided femtosecond pulses in air,” Opt. Lett. 21, 62-64 (1996).3.Miguel Rodriguez, Riad Bourayou, Guillaume Méjean, Jérôme Kasparian, Jin Yu, Estelle Salmon,Alexander Scholz, Bringfried Stecklum, Jochen Eislöffel, Uwe Laux, Artie P. Hatzes, RolandSauerbrey, Ludger Wöste, and Jean-Pierre Wolf.“Kilometer-range nonlinear propagation offemtosecond laser pulses,” Phy. Rev. E 69, 036607 (2004).4.S. A. Hosseini, Q. Luo, B. Ferland, W. Liu, N. Akozbek, G. Roy, S.L. Chin, “Effective length of filamentsmeasurement using backscattered fluorescence from nitrogen molecules,” Appl. Phys. B 77, 697-702(2003).5.R. Ackermann, K. Stelmaszcyk, P. Rohwetter, G. Mejean, E. Salmon, J. Yu, J. Kasparian, G. Mechain,V.Bergmann, S. Schaper, B. Weise, T. Kumm, K.Rethmeier, W. Kalkner, L. Wöste, and J. P. Wolf,“Triggering and guiding of megavolt discharges by laser-induced filaments under rain conditions,”Appl.Phys. Lett. 85, 5781-5783 (2004).6. F. Vidal, D. Comtois, C.-Y. Chien, A. Desparois, B. La Fontaine, T. W. Johnston, J.-C. Kieffer, H. P.Mercure, and F. A. Rizk, “Modeling the triggering of streamers in air by ultrashort laser pulses,” IEEETrans. Plasma Sci. 28, 418–433 (2000).7.J. Kasparian, M. Rodriguez, G. Méjean, J. Yu, E. Salmon, H. Wille, R. Bourayou, S. Frey, Y.-B. André,A. Mysyrowicz, R. Sauerbrey, J.-P. Wolf, and L. Wöste, “White-Light Filaments for AtmosphericAnalysis,” Science 301, 61-64 (2003).8.H. Yang, J. Zhang, W. Yu, Y. J. Li, and Z. Y. Wei,“Long plasma channels generated by femtosecondlaser pulses,” Phys. Rev. E 65, 016406(2001).9.X. Lu, Xi Ting Ting, Li Ying-Jun, and Zhang Jie, “Lifetime of the plasma channel produced by ultra-shortand ultra-high power laser pulse in the air,” Acta Physica Sinica 53, 3404-3408 (2004).10.Hui Yang, Jie Zhang, Yingjun Li, Jun Zhang, Yutong Li, Zhenglin Chen, Hao Teng, Zhiyi Wei, andZhengming Sheng, “Characteristics of self-guided laser plasma channels generated by femtosecond laserpulses in air,” Phys. Rev. E 66, 016406(2002).11.X .M .Zhao, Jean-Claude Diels, Cai Yi Wang, and Juan M. Elizondo, “Femtosecond Ultraviolet LaserPulse Induced Lightning Discharges in Gases,” IEEE J. Quantum Electron. 31. 599-612(1995).12.M.A. Biondi, “Recombination,” in Principles of Laser Plasmas, G. Bekefi, ed. pp.125-157 (New York,Wiley, 1976)#68045 - $15.00 USD Received 17 February 2006; revised 9 May 2006; accepted 10 May 2006 (C) 2006 OSA29 May 2006 / Vol. 14, No. 11 / OPTICS EXPRESS 491513. Quanli Dong, Fei Yan, Jie Zhang, Zhan Jin, Hui Yang, Zuoqiang Hao, Zhenglin Chen, Yutong Li, ZhiyiWei, and Zhengming Sheng, “The measurement and analysis of the prolonged lifetime of the plasmachannel formed by short pulse laser in air,” Acta Physica Sinica 54, 3247-3250 (2005).14. Jiansheng Liu, Zuoliang Duan, Zhinan Zeng, Xinhua Xie, Yunpei Deng, Ruxin Li, and Zhizhan Xu,“Time-resolved investigation of low-density plasma channels produced by a kilohertz femtosecond laser inair,” Phys. Rev. E 72, 026412 (2005).The generation of light filaments in air has attracted broad interest [1-4] due to their applications for lightning protection [5-6] and atmospheric remote sensing [7]. The filaments remain stable over tens of meters or more, which is much longer than the beam’s Rayleigh distance [1-3]. This self-guiding effect has been attributed to a dynamic balance between beam self-focusing (owing to the optical Kerr effect) and defocusing (owing to medium ionization). A high degree of ionization as well as a long lifetime of light filaments is preferred in practical application. Recent research on the lifetime of light filaments reported that the lifetime of a light filament could be enhanced by bringing in a second long-pulse laser after a femtosecond laser pulse mainly due to the optical detachment effect [8-10]. The electron density owing to the optical detachment effect maintains itself at about 12313310~10cm cm −− [9]. We hope to further increase the degree of ionization during the total lifetime of a plasma channel.In our experiment, we applied a high voltage electrical field in the plasma channel induced by a femtosecond laser pulse in air. Results show that the lifetime of the plasma channel had been prolonged and also the degree of ionization increased. The lifetime of the plasma channel reaches about 60 ns with a field of about 350kV/m. We investigated the variation of the lifetime of the plasma channel with the increase in electric field. In addition, we brought in a second femtosecond laser pulse and found that the lifetime of the filament can reach 200 ns with a delay of 60 ns between the first and second pulse. Finally, the lifetime of plasma channel was enhanced to 350 ns by using four sequential laser pulses, which proves the feasibility of prolonging the lifetime of plasma by employing multiple laser pulses.The experiments were performed with a 10-Hz chirped-pulse amplification Ti-sapphire laser system. A plasma channel was produced by a 2-mJ, 100-fs chirped laser pulse at 790 nm with a focusing lens of f=50 cm. An electrical field which can be adjusted in a range of 0-350kV/m was applied along the plasma channel. The experimental arrangement is shown in Fig. 1. The configuration of the electrodes here for the high voltage is sharp-point. The distance between two electrodes is about 3 cm. The variation of the electrical signals in the channel indicates the decay of electron density. And Electron decay rate is directly related to the length of plasma’s life. Therefore, we measure the lifetime of the plasma channel by detecting voltage from probe c in the channel.Fig. 1. Experimental setup; Electrodes a, b, and probe c are set close to the path of the plasmachannel induced by femtosecond laser pulse.#68045 - $15.00 USD Received 17 February 2006; revised 9 May 2006; accepted 10 May 2006(C) 2006 OSA 29 May 2006 / Vol. 14, No. 11 / OPTICS EXPRESS 4916We have measured the electrical signals when the fields are 0, 250, and 350kV/m respectively. Meanwhile, through a longitudinal diffraction detection method [14], the initial electron density was estimated at about 17310cm −and the diameter of the plasma channel was about 100m μ. The visible length of the plasma channel was over 4 cm.As shown in Fig. 2(a), the decay time of the electrical signal (defined as the duration lasting from the maximum value to 5% of the maximum value), increased by about 3 folds when the electrical field increased to 350 kV/m (dash-dotted line c). As we expected, the variation of the electrical signals in the channel showed that the lifetime of the plasma channel was prolonged when the electrical field increased. On the other hand, the solid line in Fig. 2(b), resulting from a theoretical model, which will be discussed later based on Eq. (1)-(3), depicts the evolution of electron density in the absence of an electrical field. We calculated that within 20 ns the electron density would be expected to fall to 31410−cm . Here, the initial electron density in our calculation was of the same order magnitude as the measurement in our experiment (17310cm −). Therefore, we expected that within the same 20 ns the electron density in the plasma would remain above 31410−cm . We regard this level as an indication of the lifetime of a plasma channel. In Fig. 2(a), compared to line a, line b and c indicate increased lifetimes of 40 and 60 ns respectively. Our experiment results show that an electrical field added in the plasma channel can affect the characteristics of the plasma and prolong the lifetime of the plasma channel.#68045 - $15.00 USD Received 17 February 2006; revised 9 May 2006; accepted 10 May 2006(C) 2006 OSA 29 May 2006 / Vol. 14, No. 11 / OPTICS EXPRESS 4917Fig. 2. (a) Measured electrical signals (solid line a, dashed line b, and dash-dotted line ccorrespond to electrical fields of 0V/m, 250kV/m, 350kV/m respectively); (b) Theoreticalcalculation with initial condition that 173210e n cm −=×.In order to further extend the lifetime of the plasma channel, we added a second femtosecond laser pulse with the external electrical field still in place. The delay between the two laser pulses was adjusted and the corresponding lifetime of the plasma channel is measured as shown in Fig. 3 and Fig. 4. As we can see in Fig. 3, the lifetime is prolonged to about 150 ns when the delay between two pulses is 40 ns. With a delay of 60 ns, the lifetime increases to 200 ns. As shown in Fig. 4, further increase in delay (100 ns) no longer leads to further extension of the lifetime. This is because the distance between the two laser pulses is so long that the interaction between them is less pronounced than in situations with shorter delay time.#68045 - $15.00 USD Received 17 February 2006; revised 9 May 2006; accepted 10 May 2006(C) 2006 OSA 29 May 2006 / Vol. 14, No. 11 / OPTICS EXPRESS 4918A multi-pulse scheme is employed here to reach a longer lifetime. In our experiment, we added three more laser pulses to the original laser pulse with a delay between two consecutive pulses at about 70 ns. This was done to obtain an optimal effect on the lifetime. These multiple laser pulses were generated by passing a main laser pulse through beam splitters and setting long-range fixed delays. The electrical field remained at about 350kV/m. The energy of the original pulse was 0.4 mJ and those of the later three laser pulses are all about 0.1 mJ ±0.1 mJ due to long-range propagation. The measured electrical signal is shown in Fig. 5 with a total lifetime of about 350 ns. As we can see, the signal caused by subsequent pulses is not as intense as in the double-pulse experiments conducted. This is due to the relatively low energy of later pulses. According to our double-pulse experimental results, we can expect that with relatively high energy of each later pulse at about 0.4 mJ, the lifetime of the plasma channel can be increased longer than what we acquired in Fig. 5. Therefore, we can conclude that a multi-pulse scheme with an electrical field added is efficacious for the extension of the lifetime of the plasma channel.-0.010.000.010.020.030.040.050.06e l e c t r i c a l s i g n a l (a .u .)t(ns)Fig. 3. Electrical signals in double-pulse scheme. The energies of two pulses with the delay of20 ns are 0.5 mJ and 0.4 mJ respectively. The energies of two pulses with the delay of 40 ns arealso 0.5 mJ and 0.4 mJ respectively. #68045 - $15.00 USD Received 17 February 2006; revised 9 May 2006; accepted 10 May 2006(C) 2006 OSA 29 May 2006 / Vol. 14, No. 11 / OPTICS EXPRESS 4919Fig. 4. Electrical signals in double-pulse scheme. The energies of two pulses with the delay of60 ns are 0.5 mJ respectively. The energies of two pulses with the delay of 100 ns are 0.3 mJrespectively.Fig. 5. Electrical signal in four-pulse scheme. The energy of the first pulse is 0.4 mJ, and theenergies of later pulses are all about 0.1 mJ. The delay between two contiguous pulses is 70 ns.The main mechanisms involved in the decay process of the plasma channel in a highelectrical field include the photo-ionization, impact ionization, dissociative attachments of electrons to oxygen molecules, charged particle recombination, detachments of electrons byion-ion collision, and electron diffusion. Among these effects, the attachment of electrons to oxygen molecules is detrimental to the lifetime of the plasma channel. The effect of#68045 - $15.00 USD Received 17 February 2006; revised 9 May 2006; accepted 10 May 2006 (C) 2006 OSA29 May 2006 / Vol. 14, No. 11 / OPTICS EXPRESS 4920detachments of electrons caused by ion-ion collision is relatively weak compared with the others and thus is omitted in our analysis. And the electron diffusion is a slow process, on the time scale of tens of s μ[11]. And electron generation and plasma formation are on the time scale of ns to s μ. At this time scale, effects from electron diffusion can be neglected. Therefore, we can estimate the lifetime of the plasma channel following the equation of continuity as follows [10，11] p e ep e e e n n n n tn βηα−−=∂∂ (1) p n np p e ep e pn n n n n tn ββα−−=∂∂ (2) p n np e n n n n tn βη−=∂∂ (3) where e n , p n , n n are electron density, positive ion density, and negative ion density in air respectively. α is the impact ionization coefficient. ηis the attachment rate. Initial conditions for theoretical analysis is that 173210e n cm −=×, 173210p n cm −=×, 0n n =.Through our simulation, αand ηin different electric fields did not exert a noticeable effect on the lifetime of a plasma channel. Therefore, we expect that ep βand np βmay play a role in extending the lifetime when an external electrical field is added.Without considering the effect of external electric field, a general expression of electron-ion recombination coefficient ep βas a function of electron temperature Te is [11, 12]:3120.39123110.702212(/) 2.03510,()(/) 1.13810,()0.790.21ep m s Te e N m s Te e O βββββ−−−+−−−+=×−=×−=+ (4)We take np ep ββ= in our calculation since the ion-ion recombination coefficient np β is of the same order of magnitude as the electron-ion recombination coefficient ep β.The theoretical simulation of the lifetime of the plasma channel is shown in Fig. 6. As line a, b and c shown, the lifetime of the plasma channel is prolonged from 20 ns to 60 ns as the dissociative recombination coefficient ep βand np β decrease.Potential energy curves play a role in dissociative recombination. In a favorable potential curve crossing case, a sharper falloff in this coefficient than 0.39Te −and 0.70Te −will occur with increasing incident electron energy [12]. When the external electrical field is added along the plasma channel, the incident energy of electrons will be increased. Meanwhile, Te can be assumed to thermalize at the same ambient air temperature as the gas molecules [11]. Because potential energy curves will change due to the external electrical field, we expect that a favorable potential curve crossing may exist in this case. And this can lead to a quicker falloff in ep βand np β, and corresponding extension in the lifetime as electron energy increases, as we can see from the comparison of line a, b and c shown in Fig. 6.#68045 - $15.00 USDReceived 17 February 2006; revised 9 May 2006; accepted 10 May 2006(C) 2006 OSA 29 May 2006 / Vol. 14, No. 11 / OPTICS EXPRESS 4921Fig. 6. Theoretical simulation with 417.410s α−=× and 712.510s η−=× [11]; Solid line a,dashed line b and dash-dotted line c correspond to different dissociative recombinationrates 1332.210/m s −×, 1330.810/m s −× and 1330.310/m s −× respectively.Similarly, in double-pulse and multi-pulse case, the dissociative recombination rate can decline more intensively than the case without an external electrical field and this will thus lead to an extension of the lifetime of the plasma channel. Moreover, the addition of the second and later pulses will again cause a large number of electrons due to photo-ionization [13]. With these extra electrons, the lifetime of the plasma channel will further extend.As a conclusion, characteristics of the lifetime of the plasma channel are investigated by adding an external electrical field and also extra laser pulses. The lifetime increases by 3 folds when the external electrical field is about 350kV/m in our experiment. We expect that a favorable crossing case may exist when an external electrical field is in place, and this can lead to a corresponding growth in the lifetime of the plasma channel. In addition, the lifetime of plasma channel is greatly enhanced to 350 ns by using four sequential intense 100fs (FWHM) laser pulses with the external electrical field (350kV/m). Therefore, we conclude that a multi-pulse scheme with an external electrical field added is feasible for greatly prolonging the lifetime of a plasma channel. This research is supported by a Major Basic Research project of the Shanghai Commission of Science and Technology, the Chinese Academy of Sciences, the Chinese Ministry of Science and Technology, and the Natural Science Foundation of China. #68045 - $15.00 USD Received 17 February 2006; revised 9 May 2006; accepted 10 May 2006(C) 2006 OSA 29 May 2006 / Vol. 14, No. 11 / OPTICS EXPRESS 4922。

ultrafast system瞬态吸收光谱-概述说明以及解释

ultrafast system瞬态吸收光谱-概述说明以及解释1.引言1.1 概述ultrafast system瞬态吸收光谱是一种先进的光谱分析技术，其能够实时监测物质在极短时间尺度内的光学响应过程。

通过该技术，我们可以实现对物质在纳秒至飞秒时间范围内的光谱特性进行高精度的测量和分析。

随着科学技术的不断进步，ultrafast system瞬态吸收光谱已经成为研究生物、材料科学、纳米技术等领域中不可或缺的工具。

通过对物质在极短时间尺度内的光学响应过程进行研究，我们可以更深入地了解物质的结构、性质和动态变化规律，为解决相关科学难题提供了重要的支持。

本文将深入探讨ultrafast system瞬态吸收光谱的概念、原理及其在不同应用领域中的重要性和应用价值，希望能够为读者提供全面的了解和认识。

文章结构部分的内容应包括对整篇文章的章节划分和各个章节的主要内容描述。

具体来说，可以按照以下方式进行描述："1.2 文章结构: 本文主要分为引言、正文和结论三个部分。

在引言部分中，将介绍ultrafast system瞬态吸收光谱的概念、本文的目的以及整体的文章结构。

在正文部分中，将详细阐述ultrafast system的概念、瞬态吸收光谱的原理以及其在应用领域中的具体应用。

最后，在结论部分中，将总结全文的主要内容，展望ultrafast system瞬态吸收光谱的未来发展方向，并给出本文的结束语。

"1.3 目的目的部分的内容应该明确指出本文旨在探讨ultrafast system瞬态吸收光谱的相关概念、原理和应用领域，深入探讨其在光谱分析中的重要性和价值。

通过对该主题的详细介绍和分析，旨在帮助读者更好地理解ultrafast system瞬态吸收光谱的特点、作用机制以及其在各个领域的应用情况。

最终的目的是为读者提供一份全面且清晰的指南，以便更好地了解和应用这一技术在科研和实践中的作用，为相关领域的研究和应用提供参考和帮助。

Phase and amplitude light pulse shaping using a on

专利名称：Phase and amplitude light pulse shapingusing a one-dimensional phase mask发明人：Randy A. Bartels,Jesse W. Wilson,PhilipSchlup申请号：US12119443申请日：20080512公开号：US07576907B1公开日：20090818专利内容由知识产权出版社提供专利附图：摘要：Simultaneous amplitude and phase control of ultrafast laser pulses using a single, linear (one-dimensional) liquid crystal spatial light modulator is described.Amplitude shaping is accomplished by writing a high-frequency phase grating having a spatial period much smaller than the spectral focus (over-sampling), onto the modulator, and diffracting away selected frequencies in a controllable manner, while spectral phase control is imparted by adding an appropriate slow phase bias to the modulator. The close pixel spacing, large number of pixels, and small footprint of the reflective spatial light modulator employed with an angular wavelength dispersive element in a folded Martinez stretcher, enables a simple and compact apparatus to be achieved. The high reflectivity of the spatial light modulator results in a highly efficient pulse shaper when either a prism or diffractive grating is used for the angular dispersive element. The use of a transmissive spatial light modulator in an unfolded Martinez stretcher configuration is also described.申请人：Randy A. Bartels,Jesse W. Wilson,Philip Schlup地址：Fort Collins CO US,Fort Collins CO US,Fort Collins CO US国籍：US,US,US代理机构：Cochran Freund & Young LLC代理人：Samuel M. Freund更多信息请下载全文后查看。

线性啁啾脉冲频谱干涉特性的模拟研究

线性啁啾脉冲频谱干涉特性的模拟研究董军;彭翰生;魏晓峰;胡东霞;周维;赵军普;程文雍;刘兰琴【摘要】为了研究宽带脉冲因受外界瞬态扰动而引起的相移随频谱变化的规律,利用啁啾脉冲与扰动在频域上的卷积特性,采取将频谱干涉技术和线性啁啾脉冲相结合,当两束线性啁啾脉冲在频率域相遇时,相同的频谱成分产生干涉,从其干涉图中得到随脉冲频谱变化的相对相移.根据傅里叶变换的频谱干涉技术,对从两束线性啁啾脉冲的频谱干涉图中提取相移进行了数值模拟.结果表明,对假设具有不同类型的相移进行重构,还原出随频谱变化的相位扰动.这一结果对超快光学中的瞬态测量是有帮助的.【期刊名称】《激光技术》【年(卷),期】2009(033)003【总页数】4页(P232-235)【关键词】超快光学;频域相移;频谱干涉;啁啾脉冲;滤波;时间延迟【作者】董军;彭翰生;魏晓峰;胡东霞;周维;赵军普;程文雍;刘兰琴【作者单位】中国工程物理研究院,激光聚变研究中心,绵阳,621900;中国工程物理研究院,激光聚变研究中心,绵阳,621900;中国工程物理研究院,激光聚变研究中心,绵阳,621900;中国工程物理研究院,激光聚变研究中心,绵阳,621900;中国工程物理研究院,激光聚变研究中心,绵阳,621900;中国工程物理研究院,激光聚变研究中心,绵阳,621900;中国工程物理研究院,激光聚变研究中心,绵阳,621900;中国工程物理研究院,激光聚变研究中心,绵阳,621900【正文语种】中文【中图分类】O436引言随着飞秒激光脉冲技术的飞速发展,超强超短脉冲激光与等离子体的相互作用提供了崭新的研究课题[1-3]，而频域干涉技术(Fourier-domain interferometry，FDI)在各种瞬态物理量的测量中也得到了越来越广泛的应用。

例如基于频域干涉技术探测激光诱导的等离子体[4]，光纤自相位调制的测量[5]，光纤中飞秒脉冲群延迟的测量[6]，对高功率超短脉冲激光诱导产生的等离子体波(尾场)的测量[7-9]等。

脉冲激光频域干涉技术在泵浦探测实验中的应用

脉冲激光频域干涉技术在泵浦探测实验中的应用翁继东;刘仓理;李剑峰;蔡灵仓;谭华;钟杰;王翔;马云【摘要】通过对频域干涉原理的深入研究,本文提出了一种超快时间分辨力的脉冲激光频域干涉技术.采用该技术方法可精确同步泵浦-探测实验中泵浦脉冲和探测脉冲的传输时间,其同步精度与脉冲激光器脉宽相当.本文详细论述了频域干涉技术的系统构成和工作原理,数值模拟了飞秒脉冲激光频域干涉仪的输出信号,指出当频域干涉仪输出的条纹数最少时,两脉冲之间的传输时间差即达到最小,最后通过动态实验验证了理论推导结果.【期刊名称】《光电工程》【年(卷),期】2010(037)004【总页数】5页(P34-38)【关键词】飞秒脉冲激光;频域干涉;时间分辨力;泵浦探测实验【作者】翁继东;刘仓理;李剑峰;蔡灵仓;谭华;钟杰;王翔;马云【作者单位】中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室,四川,绵阳,621900;中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室,四川,绵阳,621900;中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室,四川,绵阳,621900;中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室,四川,绵阳,621900;中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室,四川,绵阳,621900;中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室,四川,绵阳,621900;中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室,四川,绵阳,621900;中国工程物理研究院流体物理研究所冲击波物理与爆轰物理实验室,四川,绵阳,621900【正文语种】中文【中图分类】TH7440 引言研究材料在飞秒脉冲激光作用下的冲击动力学性质，需要精确测量材料在飞秒脉冲激光作用下的冲击波速度和波后粒子速度[1]，以获取材料在高压、高应变率冲击加载状态下的状态方程、熔化规律等[2]。

振动力学专业英语及词汇

振动力学专业英语及词汇振动方面的专业英语及词汇振动方面的专业英语及词汇参见《工程振动名词术语》1 振动信号的时域、频域描述振动过程 (Vibration Process)简谐振动 (Harmonic Vibration)周期振动 (Periodic Vibration)准周期振动 (Ouasi-periodic Vibration)瞬态过程 (Transient Process)随机振动过程 (Random Vibration Process)各态历经过程 (Ergodic Process)确定性过程 (Deterministic Process)振幅 (Amplitude)相位 (Phase)初相位 (Initial Phase)频率 (Frequency)角频率 (Angular Frequency)周期 (Period)复数振动 (Complex Vibration)复数振幅 (Complex Amplitude)峰值 (Peak-value)平均绝对值 (Average Absolute Value)有效值 (Effective Value，RMS Value)均值 (Mean Value，Average Value)傅里叶级数 (FS，Fourier Series)傅里叶变换 (FT，Fourier Transform)傅里叶逆变换 (IFT，Inverse Fourier Transform)离散谱 (Discrete Spectrum)连续谱 (Continuous Spectrum)傅里叶谱 (Fourier Spectrum)线性谱 (Linear Spectrum)幅值谱 (Amplitude Spectrum)相位谱 (Phase Spectrum)均方值 (Mean Square Value)方差 (Variance)协方差 (Covariance)自协方差函数 (Auto-covariance Function)互协方差函数 (Cross-covariance Function)自相关函数 (Auto-correlation Function)互相关函数 (Cross-correlation Function)标准偏差 (Standard Deviation)相对标准偏差 (Relative Standard Deviation)概率 (Probability)概率分布 (Probability Distribution)高斯概率分布(Gaussian Probability Distribution) 概率密度(Probability Density)集合平均 (Ensemble Average)时间平均 (Time Average)功率谱密度 (PSD，Power Spectrum Density)自功率谱密度 (Auto-spectral Density)互功率谱密度 (Cross-spectral Density)均方根谱密度 (RMS Spectral Density)能量谱密度 (ESD，Energy Spectrum Density)相干函数 (Coherence Function)帕斯瓦尔定理 (Parseval''''s Theorem)维纳，辛钦公式 (Wiener-Khinchin Formula2 振动系统的固有特性、激励与响应振动系统 (Vibration System)激励 (Excitation)响应 (Response)单自由度系统 (Single Degree-Of-Freedom System) 多自由度系统(Multi-Degree-Of- Freedom System) 离散化系统(Discrete System)连续体系统 (Continuous System)刚度系数 (Stiffness Coefficient)自由振动 (Free Vibration)自由响应 (Free Response)强迫振动 (Forced Vibration)强迫响应 (Forced Response)初始条件 (Initial Condition)固有频率 (Natural Frequency)阻尼比 (Damping Ratio)衰减指数 (Damping Exponent)阻尼固有频率 (Damped Natural Frequency)对数减幅系数 (Logarithmic Decrement)主频率 (Principal Frequency)无阻尼模态频率 (Undamped Modal Frequency)模态 (Mode)主振动 (Principal Vibration)振型 (Mode Shape)振型矢量 (Vector Of Mode Shape)模态矢量 (Modal Vector)正交性 (Orthogonality)展开定理 (Expansion Theorem)主质量 (Principal Mass)模态质量 (Modal Mass)主刚度 (Principal Stiffness)模态刚度 (Modal Stiffness)正则化 (Normalization)振型矩阵 (Matrix Of Modal Shape)模态矩阵 (Modal Matrix)主坐标 (Principal Coordinates)模态坐标 (Modal Coordinates)模态分析 (Modal Analysis)模态阻尼比 (Modal Damping Ratio)频响函数 (Frequency Response Function)幅频特性 (Amplitude-frequency Characteristics)相频特性 (Phase frequency Characteristics)共振 (Resonance)半功率点 (Half power Points)波德图(Bodé Plot)动力放大系数 (Dynamical Magnification Factor)单位脉冲 (Unit Impulse)冲激响应函数 (Impulse Response Function)杜哈美积分(Duhamel’s Integral)卷积积分 (Convolution Integral)卷积定理 (Convolution Theorem)特征矩阵 (Characteristic Matrix)阻抗矩阵 (Impedance Matrix)频响函数矩阵 (Matrix Of Frequency Response Function) 导纳矩阵 (Mobility Matrix)冲击响应谱 (Shock Response Spectrum)冲击激励 (Shock Excitation)冲击响应 (Shock Response)冲击初始响应谱 (Initial Shock Response Spectrum) 冲击剩余响应谱(Residual Shock Response Spectrum) 冲击最大响应谱(Maximum Shock Response Spectrum) 冲击响应谱分析(Shock Response Spectrum Analysis 3 模态试验分析模态试验 (Modal Testing)机械阻抗 (Mechanical Impedance)位移阻抗 (Displacement Impedance)速度阻抗 (Velocity Impedance)加速度阻抗 (Acceleration Impedance)机械导纳 (Mechanical Mobility)位移导纳 (Displacement Mobility)速度导纳 (Velocity Mobility)加速度导纳 (Acceleration Mobility)驱动点导纳 (Driving Point Mobility)跨点导纳 (Cross Mobility)传递函数 (Transfer Function)拉普拉斯变换 (Laplace Transform)传递函数矩阵 (Matrix Of Transfer Function)频响函数 (FRF，Frequency Response Function)频响函数矩阵 (Matrix Of FRF)实模态 (Normal Mode)复模态 (Complex Mode)模态参数 (Modal Parameter)模态频率 (Modal Frequency)模态阻尼比 (Modal Damping Ratio)模态振型 (Modal Shape)模态质量 (Modal Mass)模态刚度 (Modal Stiffness)模态阻力系数 (Modal Damping Coefficient)模态阻抗 (Modal Impedance)模态导纳 (Modal Mobility)模态损耗因子 (Modal Loss Factor)比例粘性阻尼 (Proportional Viscous Damping)非比例粘性阻尼 (Non-proportional Viscous Damping) 结构阻尼(Structural Damping，Hysteretic Damping) 复频率(ComplexFrequency)复振型 (Complex Modal Shape)留数 (Residue)极点 (Pole)零点 (Zero)复留数 (Complex Residue)随机激励 (Random Excitation)伪随机激励 (Pseudo Random Excitation)猝发随机激励 (Burst Random Excitation)稳态正弦激励 (Steady State Sine Excitation)正弦扫描激励 (Sweeping Sine Excitation)锤击激励 (Impact Excitation)频响函数的H1 估计 (FRF Estimate by H1)频响函数的H2 估计 (FRF Estimate by H2)频响函数的H3 估计 (FRF Estimate by H3)单模态曲线拟合法 (Single-mode Curve Fitting Method)多模态曲线拟合法 (Multi-mode Curve Fitting Method)模态圆 (Mode Circle)剩余模态 (Residual Mode)幅频峰值法 (Peak Value Method)实频-虚频峰值法 (Peak Real／Imaginary Method)圆拟合法 (Circle Fitting Method)加权最小二乘拟合法 (Weighting Least Squares Fitting method) 复指数拟合法 (Complex Exponential Fitting method)1.2 振动测试的名词术语1 传感器测量系统传感器测量系统 (Transducer Measuring System)传感器 (Transducer)振动传感器 (Vibration Transducer)机械接收 (Mechanical Reception)机电变换 (Electro-mechanical Conversion)测量电路 (Measuring Circuit)惯性式传感器 (Inertial Transducer，Seismic Transducer) 相对式传感器 (Relative Transducer)电感式传感器 (Inductive Transducer)应变式传感器 (Strain Gauge Transducer)电动力传感器 (Electro-dynamic Transducer)压电式传感器 (Piezoelectric Transducer)压阻式传感器 (Piezoresistive Transducer)电涡流式传感器 (Eddy Current Transducer)伺服式传感器 (Servo Transducer)灵敏度 (Sensitivity)复数灵敏度 (Complex Sensitivity)分辨率 (Resolution)频率范围 (Frequency Range)线性范围 (Linear Range)频率上限 (Upper Limit Frequency)频率下限 (Lower Limit Frequency)静态响应 (Static Response)零频率响应 (Zero Frequency Response)动态范围 (Dynamic Range)幅值上限 Upper Limit Amplitude)幅值下限 (Lower Limit Amplitude)最大可测振级 (Max．Detectable Vibration Level)最小可测振级 (Min．Detectable Vibration Level)信噪比 (S/N Ratio)振动诺模图 (Vibration Nomogram)相移 (Phase Shift)波形畸变 (Wave-shape Distortion)比例相移 (Proportional Phase Shift)惯性传感器的稳态响应(Steady Response Of Inertial Transducer)惯性传感器的稳击响应 (Shock Response Of Inertial Transducer) 位移计型的频响特性(Frequency Response Characteristics Vibrometer)加速度计型的频响特性(Frequency Response Characteristics Accelerometer) 幅频特性曲线 (Amplitude-frequency Curve) 相频特性曲线 (Phase-frequency Curve)固定安装共振频率 (Mounted Resonance Frequency)安装刚度 (Mounted Stiffness)有限高频效应 (Effect Of Limited High Frequency)有限低频效应 (Effect Of Limited Low Frequency)电动式变换 (Electro-dynamic Conversion)磁感应强度 (Magnetic Induction， Magnetic Flux Density)磁通 (Magnetic Flux)磁隙 (Magnetic Gap)电磁力 (Electro-magnetic Force)相对式速度传 (Relative Velocity Transducer)惯性式速度传感器 (Inertial Velocity Transducer)速度灵敏度 (Velocity Sensitivity)电涡流阻尼 (Eddy-current Damping)无源微(积)分电路 (Passive Differential (Integrate) Circuit) 有源微(积)分电路(Active Differential (Integrate) Circuit) 运算放大器(Operational Amplifier)时间常数 (Time Constant)比例运算 (Scaling)积分运算 (Integration)微分运算 (Differentiation)高通滤波电路 (High-pass Filter Circuit)低通滤波电路 (Low-pass Filter Circuit)截止频率 (Cut-off Frequency)压电效应 (Piezoelectric Effect)压电陶瓷 (Piezoelectric Ceramic)压电常数 (Piezoelectric Constant)极化 (Polarization)压电式加速度传感器 (Piezoelectric Acceleration Transducer) 中心压缩式 (Center Compression Accelerometer)三角剪切式 (Delta Shear Accelerometer)压电方程 (Piezoelectric Equation)压电石英 (Piezoelectric Quartz)电荷等效电路 (Charge Equivalent Circuit)电压等效电路 (Voltage Equivalent Circuit)电荷灵敏度 (Charge Sensitivity)电压灵敏度 (Voltage Sensitivity)电荷放大器 (Charge Amplifier)适调放大环节 (Conditional Amplifier Section)归一化 (Uniformization)电荷放大器增益 (Gain Of Charge Amplifier)测量系统灵敏度 (Sensitivity Of Measuring System)底部应变灵敏度 (Base Strain Sensitivity)横向灵敏度 (Transverse Sensitivity)地回路 (Ground Loop)力传感器 (Force Transducer)力传感器灵敏度 (Sensitivity Of Force Transducer)电涡流 (Eddy Current)前置器 (Proximitor)间隙-电压曲线 (Voltage vs Gap Curve)间隙-电压灵敏度 (Voltage vs Gap Sensitivity)压阻效应 (Piezoresistive Effect)轴向压阻系数 (Axial Piezoresistive Coefficient)横向压阻系数 (Transverse Piezoresistive Coefficient)压阻常数 (Piezoresistive Constant)单晶硅 (Monocrystalline Silicon)应变灵敏度 (Strain Sensitivity)固态压阻式加速度传感器(Solid State Piezoresistive Accelerometer) 体型压阻式加速度传感器 (Bulk Type Piezoresistive Accelerometer) 力平衡式传感器 (Force Balance Transducer) 电动力常数 (Electro-dynamic Constant)机电耦合系统 (Electro-mechanical Coupling System)2 检测仪表、激励设备及校准装置时间基准信号 (Time Base Signal)李萨茹图 (Lissojous Curve)数字频率计 (Digital Frequency Meter)便携式测振表 (Portable Vibrometer)有效值电压表 (RMS Value Voltmeter)峰值电压表 (Peak-value Voltmeter)平均绝对值检波电路 (Average Absolute Value Detector)峰值检波电路 (Peak-value Detector)准有效值检波电路 (Quasi RMS Value Detector)真有效值检波电路 (True RMS Value Detector)直流数字电压表 (DVM，DC Digital Voltmeter)数字式测振表 (Digital Vibrometer)A/D 转换器 (A/D Converter)D/A 转换器 (D/A Converter)相位计 (Phase Meter)电子记录仪 (Lever Recorder)光线示波器 (Oscillograph)振子 (Galvonometer)磁带记录仪 (Magnetic Tape Recorder)DR 方式(直接记录式) (Direct Recorder)FM 方式(频率调制式) (Frequency Modulation)失真度 (Distortion)机械式激振器 (Mechanical Exciter)机械式振动台 (Mechanical Shaker)离心式激振器 (Centrifugal Exciter)电动力式振动台 (Electro-dynamic Shaker)电动力式激振器 (Electro-dynamic Exciter)液压式振动台 (Hydraulic Shaker)液压式激振器 (Hydraulic Exciter)电液放大器 (Electro-hydraulic Amplifier)磁吸式激振器 (Magnetic Pulling Exciter)涡流式激振器 (Eddy Current Exciter)压电激振片 (Piezoelectric Exciting Elements)冲击力锤 (Impact Hammer)冲击试验台 (Shock Testing Machine)激振控制技术 (Excitation Control Technique)波形再现 (Wave Reproduction)压缩技术 (Compression Technique)均衡技术 (Equalization Technique)交越频率 (Crossover Frequency)综合技术 (Synthesis Technique)校准 (Calibration)分部校准 (Calibration for Components in system) 系统校准 (Calibration for Over-all System)模拟传感器 (Simulated Transducer)静态校准 (Static Calibration)简谐激励校准 (Harmonic Excitation Calibration) 绝对校准 (Absolute Calibration)相对校准 (Relative Calibration)比较校准 (Comparison Calibration)标准振动台 (Standard Vibration Exciter)读数显微镜法 (Microscope-streak Method)光栅板法 (Ronchi Ruling Method)光学干涉条纹计数法 (Optical Interferometer Fringe Counting Method)光学干涉条纹消失法(Optical Interferometer Fringe Disappearance Method) 背靠背安装 (Back-to-back Mounting) 互易校准法 (Reciprocity Calibration)共振梁 (Resonant Bar)冲击校准 (Impact Exciting Calibration)摆锤冲击校准 (Ballistic Pendulum Calibration)落锤冲击校准 (Drop Test Calibration)振动和冲击标准 (Vibration and Shock Standard)迈克尔逊干涉仪 (Michelson Interferometer)摩尔干涉图象 (Moire Fringe)参考传感器 (Reference Transducer)3 频率分析及数字信号处理带通滤波器 (Band-pass Filter)半功率带宽 (Half-power Bandwidth)3 dB 带宽 (3 dB Bandwidth)等效噪声带宽 (Effective Noise Bandwidth)恒带宽 (Constant Bandwidth)恒百分比带宽 (Constant Percentage Bandwidth)1/N 倍频程滤波器 (1/N Octave Filter)形状因子 (Shape Factor)截止频率 (Cut-off Frequency)中心频率 (Centre Frequency)模拟滤波器 (Analog Filter)数字滤波器 (Digital Filter)跟踪滤波器 (Tracking Filter)外差式频率分析仪 (Heterodyne Frequency Analyzer) 逐级式频率分析仪 (Stepped Frequency Analyzer)扫描式频率分析仪 (Sweeping Filter Analyzer)混频器 (Mixer)RC 平均 (RC Averaging)平均时间 (Averaging Time)扫描速度 (Sweeping Speed)滤波器响应时间 (Filter Response Time)离散傅里叶变换 (DFT，Discrete Fourier Transform) 快速傅里叶变换 (FFT，Fast Fourier Transform)抽样频率 (Sampling Frequency)抽样间隔 (Sampling Interval)抽样定理 (Sampling Theorem)抗混滤波 (Anti-aliasing Filter)泄漏 (Leakage)加窗 (Windowing)窗函数 (Window Function)截断 (Truncation)频率混淆 (Frequency Aliasing)乃奎斯特频率 (Nyquist Frequency)矩形窗 (Rectangular Window)汉宁窗 (Hanning Window)凯塞-贝塞尔窗 (Kaiser-Bessel Window)平顶窗 (Flat-top Window)平均 (Averaging)线性平均 (Linear Averaging)指数平均 (Exponential Averaging)峰值保持平均 (Peak-hold Averaging)时域平均 (Time-domain Averaging)谱平均 (Spectrum Averaging)重叠平均 (Overlap Averaging)栅栏效应 (Picket Fence Effect)吉卜斯效应 (Gibbs Effect)基带频谱分析 (Base-band Spectral Analysis)选带频谱分析 (Band Selectable Sp4ctralAnalysis)细化 (Zoom)数字移频 (Digital Frequency Shift)抽样率缩减 (Sampling Rate Reduction)功率谱估计 (Power Spectrum Estimate)相关函数估计 (Correlation Estimate)频响函数估计 (Frequency Response Function Estimate) 相干函数估计 (Coherence Function Estimate)冲激响应函数估计 (Impulse Response Function Estimate) 倒频谱 (Cepstrum)功率倒频谱 (Power Cepstrum)幅值倒频谱 (Amplitude Cepstrum)倒频率 (Quefrency)4 旋转机械的振动测试及状态监测状态监测 (Condition Monitoring)故障诊断 (Fault Diagnosis)转子 (Rotor)转手支承系统 (Rotor-Support System)振动故障 (Vibration Fault)轴振动 (Shaft Vibration)径向振动 (Radial Vibration)基频振动 (Fundamental Frequency Vibration)基频检测 (Fundamental Frequency Component Detecting) 键相信号 (Key-phase Signal)正峰相位 (+Peak Phase)高点 (High Spot)光电传感器 (Optical Transducer)同相分量 (In-phase Component)正交分量 (Quadrature Component)跟踪滤波 (Tracking Filter)波德图 (Bode Plot)极坐标图 (Polar Plot)临界转速 (Critical Speed)不平衡响应 (Unbalance Response)残余振幅 (Residual Amplitude)方位角 (Attitude Angle)轴心轨迹 (Shaft Centerline Orbit)正进动 (Forward Precession)同步正进动 (Synchronous Forward Precession)反进动 (Backward Precession)正向涡动 (Forward Whirl)反向涡动 (Backward Whirl)油膜涡动 (Oil Whirl)油膜振荡 (Oil Whip)轴心平均位置(Average Shaft Centerline Position) 复合探头(Dual Probe)振摆信号 (Runout Signal)电学振摆 (Electrical Runout)机械振摆 (Mechanical Runout)慢滚动向量 (Slow Roll Vector)振摆补偿 (Runout Compensation)故障频率特征(Frequency Characteristics Of Fault) 重力临界(Gravity Critical)对中 (Alignment)双刚度转子 (Dual Stiffness Rotor)啮合频率 (Gear-mesh Frequency)间入简谐分量 (Interharmonic Component)边带振动 (Side-band Vibration)三维频谱图 (Three Dimensional Spectral Plot)瀑布图 (Waterfall Plot)级联图 (Cascade Plot)阶次跟踪 (Order Tracking)阶次跟踪倍乘器 (Order Tracking Multiplier)监测系统 (Monitoring System)适调放大器 (Conditional Amplifier)趋势分析 (Trend Analysis)倒频谱分析 (Cepstrum Analysis) 直方图 (Histogram)确认矩阵 (Confirmation Matrix) 通频幅值 (Over-all Amplitude) 幅值谱 (Amplitude Spectrum)相位谱 (Phase Spectrum)报警限 (Alarm Level)。

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Abstract: An ultrafast pulse shaper, capable of both phase and amplitude shaping, is constructed using a single high-resolution liquid crystal phase mask. The shaper is calibrated with an inline spectral interferometry technique. Amplitude shaping is accomplished by writing to the mask a phase grating, whose period is smaller than the spectral focus, diffracting away selected frequencies in a controllable manner.
References and links
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#84226 - $15.00 USD
Received 20 Jun 2007; revised 28 Jun 2007; accepted 29 Jun 2007; published 5 Jul 2007
(C) 2007 OSA
9 July 2007 / Vol. 15, No. 14 / OPTICS EXPRESS 8979
Electrical and Computer Engineering Department, Colorado State University, 1320 Campus Delivery, Fort Collins, CO 80523, USA *Corresponding author: bartels@
© 2007 Optical Society of America
OCIS codes: (230.3720) Liquid-crystal devices; (230.6120) Spatial light modulators; (320.5540) Ultrafast Pulse shaping
Ultrafast phase and amplitude pulse shaping with a single, one-dimensional, high-resolution phase mask.
Jesse W. Wilson, Philip Schlup, and Randy A. Bartels*
1.
Introductiቤተ መጻሕፍቲ ባይዱn
Programmable ultrafast optical pulse shapers are ubiquitous, with applications ranging from simple dispersion control to carefully shaped laser pulses used for coherent control of quantum dynamics [1, 2, 3]. While many applications utilize spectral phase-only shaping for simplicity, one also needs control over amplitude to access a complete range of temporal shapes, e.g. square and sinc pulses. Such control in the standard zero-dispersion Martinez stretcher has been implemented with pairs of liquid crystal spatial light modulators (LC-SLMs) [4], volume Bragg gratings written with an acousto-optic modulator (AOM) crystal [5], and recently by a two-dimensional (2D) LC-SLM with a blazed phase grating in the direction lacking spectral dispersion [6]. A complementary technology, acoust