掺铥光纤激光器
连续掺铥光纤激光器1900nm2100nm
连续掺铥光纤激光器（1900nm-2100nm）
V-Gen的VCFL-T系列激光器是单模连续、掺铥光纤激光器。
凭借其领先的技术优势，单模（M2<1.1）光束为超精密应用提供了理想光束性能，如非金属材料处理、精密加工、焊接等。
优点：
为OEM服务
免维护节约操作成本
重量轻、体积小易于集成
参数设置简单、可通过PC或笔记本电脑测试
符合工业标准
可大幅度调谐参数
应用范围:
塑料焊接、切割和打标
非金属材料处理
光谱学
医疗
主要特点：
RS232和TTL接口
波长1900-210nm
最大20W输出功率
最大10KHz直接调制
高电光转换效率（＞20%）
单模光束质量（M2<1.1）
强制风冷利于系统有效散热
可选输出准直器用于各种输出光斑直径
光纤长度cm 300(其他可选)
输出光纤准直器mm 6mm直径（其他可选）输出光束质量M2<1.1。
掺铥光纤激光器的研究
摘要掺铥（Tm3+）光纤激光器的研究和应用最近几年来受到了国际科技界的广泛重视。
因为其成本低、易于制作等特点，而且工作波长对目前和将来的某些应用尤其重要，例如在光通信、医学、传感器和光谱学等领域。
本文共分五章：第一章介绍了光纤激光器的结构和工作原理等；第二章和第三章从不同的基质材料分别介绍了两种掺铥光纤激光器；第四章介绍了铥作为敏化剂的铥钬共掺的光纤激光器；第五章综合了近几年来掺铥光纤激光器的发展现状。
关键词：光纤激光器，频率上转换，铥，钬AbstractRecent years, people of worldwide pay attention to the research and application of Tm3+-doped fiber laser. Because of its low cost and easy manufacture, and the working wavelength is much more important in some areas now and in the future, such as optical fiber communication, medical science, the spectrum learns and so on.This paper includes five chapters. The first one introduces the structure and working reason. The second and third ones introduce the two kinds of Tm3+-doped fiber laser from different basic materials. The forth one introduces Tm:Ho-doped fiber laser. And the fifth one introduces the development of Tm3+-doped fiber laser in recent years.Keyword: fiber laser, frequency upconversion, Tm, Ho目录绪论 (4)第一章光纤激光器综述1.1 光纤激光器的基本结构和工作原理 (5)1.2 光纤激光器的优点 (9)第二章掺铥氟化物光纤激光器2.1 掺铥氟化锆光纤激光器 (11)2.2 掺铥氟化物上转换光纤激光器 (12)第三章掺铥石英光纤激光器3.1 掺铥石英单模光纤激光器 (18)3.2 掺铥石英光纤的频率上转换 (21)第四章铥钬共掺光纤激光器4.1 铥钬共掺包层泵浦石英光纤激光器 (28)4.2 高效率铥敏化的掺钬CW氟化物光纤激光器 (33)第五章掺铥光纤激光器的研究现状5.1 掺铥氟化物光纤激光器 (38)5.2掺铥石英光纤激光器 (41)5.3结束语 (42)参考文献 (43)绪论信息技术已成为经济发展、社会进步的关键。
掺铥光纤激光器的理论研究的开题报告
掺铥光纤激光器的理论研究的开题报告研究背景：近年来，掺铥光纤激光器成为了研究的热点之一，主要因为掺铥光纤激光器具有很多优点，比如稳定性好、寿命长、功率大、占用空间小等。
掺铥光纤激光器的应用也非常广泛，在通信、制造、医疗等领域都有着重要的应用。
研究目的：本研究旨在探究掺铥光纤激光器的理论，以提高掺铥光纤激光器的性能和应用。
研究内容：1. 掌握掺铥光纤激光器的基本原理和工作原理。
2. 研究掺铥光纤激光器的发展历史以及现有技术的优缺点。
3. 分析掺铥光纤激光器中掺铥离子的作用机理和与光纤材料的相互作用。
4. 建立数学模型以及对掺铥光纤激光器进行仿真实验。
5. 探究掺铥光纤激光器在不同工况下的性能特点。
6. 分析掺铥光纤激光器的制备工艺以及掺铥光纤激光器的检测方法。
预期成果：通过本研究，预计得到以下成果：1. 深入了解掺铥光纤激光器的基本原理和工作原理。
2. 详细分析掺铥光纤激光器的现有技术，了解其优缺点。
3. 探究掺铥光纤激光器性能特点，建立数学模型以及进行仿真实验。
4. 提高掺铥光纤激光器的性能和应用，为掺铥光纤激光器在制造、医疗等领域的应用提供参考意见。
研究方法：本研究主要采用以下方法：1. 文献综述：对掺铥光纤激光器的相关文献进行阅读和分析，了解其发展历史、现有技术以及优缺点。
2. 数学模型：根据掺铥光纤激光器的基本原理和工作原理，建立数学模型，进行仿真实验分析。
3. 实验研究：对掺铥光纤激光器进行实验研究，验证理论分析的准确性。
研究意义：本研究对于提高掺铥光纤激光器的性能和应用具有重要的意义，不仅有助于推动掺铥光纤激光器技术的发展，还可以为该领域的研究者提供理论、技术和实验方面的参考，为推动掺铥光纤激光器的应用和发展做出贡献。
掺铒脉冲光纤激光器及其泵浦的掺铥光纤激光器研究
掺铒脉冲光纤激光器及其泵浦的掺铥光纤激光器研究摘要：掺铒脉冲光纤激光器和掺铥光纤激光器是目前应用最广泛的激光器之一。
本文将综述掺铒脉冲光纤激光器和掺铥光纤激光器的特点、优点、应用以及泵浦方式的研究进展。
关键词：掺铒激光器、掺铥激光器、波长、光谱宽度、泵浦掺铒脉冲光纤激光器的研究掺铒脉冲光纤激光器是基于掺铒光纤而成，具有很高的光谱宽度、很短的脉冲宽度、很高的功率和能量密度。
掺铒脉冲光纤激光器可以产生各种光谱波长的脉冲，从红外到紫外光谱覆盖范围很广。
它具有以下特点：（1）修正倍频技术通过修正倍频技术，可以在掺铒光纤激光器中产生许多有用的波长，从而增加光谱范围。
同时，还可以实现国际上制定的通讯波长标准。
（2）高峰值功率掺铒脉冲光纤激光器的高峰值功率可以达到数兆瓦或以上，具有很大的应用潜力。
（3）极短脉冲掺铒脉冲光纤激光器的脉冲宽度可以降低到微秒、毫秒乃至纳秒的级别，而且可以产生超短脉冲，频率可以从kHz到GHz。
（4）宽谱输出掺铒脉冲光纤激光器具有宽谱输出的特点，可以实现波长可调性。
掺铒脉冲光纤激光器的应用随着科技的不断发展，掺铒脉冲光纤激光器在医学、制造、通讯、摄影和光学仪器等领域得到广泛的应用。
（1）医学掺铒脉冲光纤激光器的超短脉冲可以用于眼科手术，如白内障手术和近视手术。
（2）制造掺铒脉冲光纤激光器可以用于制造高精度光学元件、雕刻和刻蚀微观结构等。
（3）通讯掺铒脉冲光纤激光器可以用于光纤通信，如光纤传输、光纤传感和光纤通道。
（4）摄影和光学仪器掺铒脉冲光纤激光器可以用于激光闪光灯、数字相机、测距仪、激光投影和光学显微镜等。
掺铥光纤激光器的研究掺铥光纤激光器是基于掺铥光纤而成，具有很窄的光谱宽度和高的功率效率。
掺铥光纤激光器可产生波长在约790-1600nm的激光。
它具有以下特点：（1）急冷敏捷调制技术掺铥光纤激光器具有急冷敏捷调制技术，可以使激光的输出被瞬时开启或关闭，从而提高激光的调制速度。
（2）能量密度高掺铥光纤激光器的能量密度非常高，可以达到100mJ，这是其他激光器无法比拟的。
掺铒光纤激光器原理
掺铒光纤激光器原理一、概述掺铒光纤激光器是一种基于掺铒光纤（Er-doped fiber）的激光装置，具有输出功率高、调制带宽宽、转换效率高等优点，被广泛应用于激光手术刀、激光雷达、激光打标、光通信和能量激光光源等领域。
本文将详细介绍掺铒光纤激光器的原理和构成。
二、原理1. 掺铒光纤的结构与特性掺铒光纤是由玻璃材料制成的，其结构类似于普通光纤，由包层、掺铒核心和侧面反射层组成。
铒元素在光纤中的浓度较高，可以激发激光振荡。
掺铒光纤具有较高的增益系数，适合产生激光。
2. 激光振荡过程当泵浦光照射掺铒光纤时，铒离子受激发射出电磁波，经过谐振腔反射和损耗，最终形成激光振荡。
在这个过程中，泵浦光的强度、波长和掺铒光纤的结构参数都会影响激光的输出功率和波长。
3. 谐振腔谐振腔是掺铒光纤激光器的关键组成部分，由两个反射镜组成。
其中一个反射镜固定在激光器内部，另一个需要通过外部调节来保证激光在特定波长范围内输出。
谐振腔的长度会影响激光的波长和输出功率。
三、构成1. 泵浦源泵浦源是提供能量的设备，通常采用高强度半导体激光器作为泵浦光源。
泵浦光的波长通常在800-900nm范围内，可以根据掺铒光纤的特性进行调整。
2. 掺铒光纤掺铒光纤是激光振荡的核心部件，决定了激光的输出性质。
通常选用具有较高铒离子浓度的光纤，以获得较高的增益系数和激光输出功率。
3. 反射镜反射镜是构成谐振腔的关键部件，通常采用高反射率的光学镜片。
其中一个反射镜固定在激光器内部，另一个需要通过外部调节来保证激光在特定波长范围内输出。
4. 驱动与控制电路驱动与控制电路是掺铒光纤激光器的核心部分，负责控制泵浦光的强度、波长和照射时间等参数，以保证激光的稳定输出。
同时，还需要监测激光的输出功率、波长和稳定性等指标，以便进行调节和控制。
四、应用领域1. 激光手术刀：掺铒光纤激光器具有较短的波长（2μm），可以穿透组织较浅，适用于激光手术刀领域。
通过调节泵浦光的强度和输出功率，可以控制激光的切割深度和宽度。
高功率连续波掺铥光纤激光器研究进展
第38卷，第5期红外1文章编号：1672-8785(2〇17)〇5-0001-〇7高功率连续波掺铥光纤激光器研究进展张伟^张嘉阳^吴闻迪1余婷1叶锡生1(1.中国科学院上海光学精密机械研究所，上海201800 ;2.中国科学院大学，北京1〇〇〇必）摘要：掺铥光纤激光器（Tm-Doped Fiber Laser,TDFL)具有结构装凑、散热性能优良、光束质量好、非钱性效应阈值高等优点，其量子转换效率在理论上可达200% …TDFL产生的1.7〜2.1 nm激光在多个领域具有广泛应用。
筒要介绍了 Tm3+离子的吸收谱和能续结构、T D F L三种系捕方式的优缺点以及国内外高功率T D F L的研究进展，并就其未来发展给出了初步看法.关键词：掺铥先纤激光器；泵浦方式；高功率中图分类号：TN248 文献标志码：A D O I:10.3969/j.issn.l672-8785.2017.05.001 Research Progress of High Power Continuous-waveTm-doped Fiber LaserZHANG Wei 1气ZHANG Jia-yang WU Wen-di \YU Ting \YE Xi-sheng 1(1. Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai201800, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China) Abstract: Tm-doped Fiber Lasers (TDFL) have the advantages of compact structure, excellent coolingcapacity, good beam quality and high non-linear effect threshold etc. Theoretically, its quantum conversion efficiency can be up to 200%. The laser generated by TDFLs at the wavelengths from 1.7 \xmto 2.1 ]xm has wide applications in many fields. The absorption spectrum and level structure of Tm3+,the advantages and disadvantages of three different pumping methods and the research progress of highpower TDFLs at home and abroad are presented in brief. Finally, the preliminary view on the futuredevelopment of high power TDFLs is given.Key words: Tm-doped fiber laser; pumping method; high power〇引言辱在t t i l率，satt着1w就提出了将光评应用于激光器的思路。
掺铥光纤激光器市场调研报告
掺铥光纤激光器市场调研报告正文目录1 掺铥光纤激光器市场概述1.1 产品定义及统计范围1.2 按照不同产品类型，掺铥光纤激光器主要可以分为如下几个类别1.2.1 不同产品类型掺铥光纤激光器销售额增长趋势2017 VS 2021 VS 20281.2.2 1900 nm1.2.3 1950 nm1.2.4 2000 nm1.2.5 其他1.3 从不同应用，掺铥光纤激光器主要包括如下几个方面1.3.1 不同应用掺铥光纤激光器销售额增长趋势2017 VS 2021 VS 20281.3.1 工业领域1.3.2 医疗领域1.3.3 实验室1.3.4 其他1.4 掺铥光纤激光器行业背景、发展历史、现状及趋势1.4.1 掺铥光纤激光器行业目前现状分析1.4.2 掺铥光纤激光器发展趋势2 全球掺铥光纤激光器总体规模分析2.1 全球掺铥光纤激光器供需现状及预测（2017-2028）2.1.1 全球掺铥光纤激光器产能、产量、产能利用率及发展趋势（2017-2028）2.1.2 全球掺铥光纤激光器产量、需求量及发展趋势（2017-2028）2.1.3 全球主要地区掺铥光纤激光器产量及发展趋势（2017-2028）2.2 中国掺铥光纤激光器供需现状及预测（2017-2028）2.2.1 中国掺铥光纤激光器产能、产量、产能利用率及发展趋势（2017-2028）2.2.2 中国掺铥光纤激光器产量、市场需求量及发展趋势（2017-2028）2.3 全球掺铥光纤激光器销量及销售额2.3.1 全球市场掺铥光纤激光器销售额（2017-2028）2.3.2 全球市场掺铥光纤激光器销量（2017-2028）2.3.3 全球市场掺铥光纤激光器价格趋势（2017-2028）3 全球与中国主要厂商市场份额分析3.1 全球市场主要厂商掺铥光纤激光器产能市场份额3.2 全球市场主要厂商掺铥光纤激光器销量（2017-2022）3.2.1 全球市场主要厂商掺铥光纤激光器销量（2017-2022）3.2.2 全球市场主要厂商掺铥光纤激光器销售收入（2017-2022）3.2.3 全球市场主要厂商掺铥光纤激光器销售价格（2017-2022）3.2.4 2021年全球主要生产商掺铥光纤激光器收入排名3.3 中国市场主要厂商掺铥光纤激光器销量（2017-2022）3.3.1 中国市场主要厂商掺铥光纤激光器销量（2017-2022）3.3.2 中国市场主要厂商掺铥光纤激光器销售收入（2017-2022）3.3.3 中国市场主要厂商掺铥光纤激光器销售价格（2017-2022）3.3.4 2021年中国主要生产商掺铥光纤激光器收入排名3.4 全球主要厂商掺铥光纤激光器产地分布及商业化日期3.5 全球主要厂商掺铥光纤激光器产品类型列表3.6 掺铥光纤激光器行业集中度、竞争程度分析3.6.1 掺铥光纤激光器行业集中度分析：2021全球Top 5生产商市场份额3.6.2 全球掺铥光纤激光器第一梯队、第二梯队和第三梯队生产商（品牌）及市场份额3.7 新增投资及市场并购活动4 全球掺铥光纤激光器主要地区分析4.1 全球主要地区掺铥光纤激光器市场规模分析：2017 VS 2021VS 20284.1.1 全球主要地区掺铥光纤激光器销售收入及市场份额（2017-2022年）4.1.2 全球主要地区掺铥光纤激光器销售收入预测（2023-2028年）4.2 全球主要地区掺铥光纤激光器销量分析：2017 VS 2021 VS 20284.2.1 全球主要地区掺铥光纤激光器销量及市场份额（2017-2022年）4.2.2 全球主要地区掺铥光纤激光器销量及市场份额预测（2023-2028）4.3 北美市场掺铥光纤激光器销量、收入及增长率（2017-2028）4.4 欧洲市场掺铥光纤激光器销量、收入及增长率（2017-2028）4.5 中国市场掺铥光纤激光器销量、收入及增长率（2017-2028）4.6 日本市场掺铥光纤激光器销量、收入及增长率（2017-2028）4.7 韩国市场掺铥光纤激光器销量、收入及增长率（2017-2028）4.8 中国台湾市场掺铥光纤激光器销量、收入及增长率（2017-2028）5 全球掺铥光纤激光器主要生产商分析5.1 Thorlabs5.1.1 Thorlabs基本信息、掺铥光纤激光器生产基地、销售区域、竞争对手及市场地位5.1.2 Thorlabs掺铥光纤激光器产品规格、参数及市场应用5.1.3 Thorlabs掺铥光纤激光器销量、收入、价格及毛利率（2017-2022）5.1.4 Thorlabs公司简介及主要业务5.1.5 Thorlabs企业最新动态5.2 IPG Photonics5.2.1 IPG Photonics基本信息、掺铥光纤激光器生产基地、销售区域、竞争对手及市场地位5.2.2 IPG Photonics掺铥光纤激光器产品规格、参数及市场应用5.2.3 IPG Photonics掺铥光纤激光器销量、收入、价格及毛利率（2017-2022）5.2.4 IPG Photonics公司简介及主要业务5.2.5 IPG Photonics企业最新动态5.3 Fiberlabs Inc5.3.1 Fiberlabs Inc基本信息、掺铥光纤激光器生产基地、销售区域、竞争对手及市场地位5.3.2 Fiberlabs Inc掺铥光纤激光器产品规格、参数及市场应用5.3.3 Fiberlabs Inc掺铥光纤激光器销量、收入、价格及毛利率（2017-2022）5.3.4 Fiberlabs Inc公司简介及主要业务5.3.5 Fiberlabs Inc企业最新动态5.4 Techwin Industry5.4.1 Techwin Industry基本信息、掺铥光纤激光器生产基地、销售区域、竞争对手及市场地位5.4.2 Techwin Industry掺铥光纤激光器产品规格、参数及市场应用5.4.3 Techwin Industry掺铥光纤激光器销量、收入、价格及毛利率（2017-2022）5.4.4 Techwin Industry公司简介及主要业务5.4.5 Techwin Industry企业最新动态6 不同产品类型掺铥光纤激光器分析6.1 全球不同产品类型掺铥光纤激光器销量（2017-2028）6.1.1 全球不同产品类型掺铥光纤激光器销量及市场份额（2017-2022）6.1.2 全球不同产品类型掺铥光纤激光器销量预测（2023-2028）6.2 全球不同产品类型掺铥光纤激光器收入（2017-2028）6.2.1 全球不同产品类型掺铥光纤激光器收入及市场份额（2017-2022）6.2.2 全球不同产品类型掺铥光纤激光器收入预测（2023-2028）6.3 全球不同产品类型掺铥光纤激光器价格走势（2017-2028）7 不同应用掺铥光纤激光器分析7.1 全球不同应用掺铥光纤激光器销量（2017-2028）7.1.1 全球不同应用掺铥光纤激光器销量及市场份额（2017-2022）7.1.2 全球不同应用掺铥光纤激光器销量预测（2023-2028）7.2 全球不同应用掺铥光纤激光器收入（2017-2028）7.2.1 全球不同应用掺铥光纤激光器收入及市场份额（2017-2022）7.2.2 全球不同应用掺铥光纤激光器收入预测（2023-2028）7.3 全球不同应用掺铥光纤激光器价格走势（2017-2028）8 上游原料及下游市场分析8.1 掺铥光纤激光器产业链分析8.2 掺铥光纤激光器产业上游供应分析8.2.1 上游原料供给状况8.2.2 原料供应商及联系方式8.3 掺铥光纤激光器下游典型客户8.4 掺铥光纤激光器销售渠道分析9 行业发展机遇和风险分析9.1 掺铥光纤激光器行业发展机遇及主要驱动因素9.2 掺铥光纤激光器行业发展面临的风险9.3 掺铥光纤激光器行业政策分析9.4 掺铥光纤激光器中国企业SWOT分析10 研究成果及结论11 附录11.1 研究方法11.2 数据来源11.2.1 二手信息来源11.2.2 一手信息来源11.3 数据交互验证11.4 免责声明。
掺铥光纤激光器的应用
掺铥光纤激光器的应用
光纤激光器具有理想的光束质量、超高的转换效率、免维护、高稳定性以及冷却效率高、体积小等优点，具有许多其他激光器无可比拟的技术优越性。
2μm掺铥光纤激光器由于其高效率、高输出功率、对人眼安全、且位于透过率良好的“大气窗口”等特性在科研领域有着巨大吸引力，它在材料处理、遥感、生物医学和国防领域有着广泛应用前景。
掺铥光纤激光器的应用
随着光纤制作技术的日臻成熟、成本逐渐降低，2μm波段掺铥光纤激光器的应用也越来越广泛，下面介绍几个2μm波段掺铥光纤激光器的典型应用。
一军事上
2μm波段位于透过率良好的“大气窗口”，在激光武器中具有广阔的应用前景。
陆军可将高功率2μm光纤激光器安装在未来战斗系统(FCS)的地面车辆上，然后利用这种激光武器对付空对地导弹、火箭弹、迫击炮等。
空军则可进行地对空导弹打击、导弹防御、反卫星等。
海军利用激光武器系统主要对付反舰导弹、有人机、无人机、小型舰艇等目标。
海军陆战队则可在保证附加破坏效应最小的条件下实现精确打击。
在防空、光电对抗等活动中，光纤激光器更有短期实现的可能。
高功率2μm光纤激光器正成为一种将来安装在运输飞机、地面车辆、甚至可能是便携式系统的有前途的武器级固体激光器系统。
在飞机和导弹导航中，2μm光纤激光器可用做激光雷达。
二生物医学
医学上，可作为一种高精度的眼睛手术刀，由于人眼中的水分子对2μm。
掺镱光纤激光器工作原理
掺镱光纤激光器工作原理掺铒光纤激光器作为一种高效率、高功率、高光质、可调谐性和可重复性良好的激光器，被广泛地应用于各个领域。
而掺镱光纤激光器也是一种常见的激光器，它与掺铒光纤激光器相似，但通过掺入不同的离子来实现不同的工作波长。
下面将为大家介绍掺镱光纤激光器的工作原理。
掺镱光纤激光器的工作原理就是利用掺镱光纤的激活离子镱离子来实现激光的放大和发射。
掺镱光纤激光器的能量转化过程大致可以分为三个阶段：抽运阶段、饱和阶段和发射阶段。
在抽运阶段，由激光二极管提供泵浦能量，使得掺镱光纤中的镱离子激发跃迁到较高的能级，形成了一个高能级的激发态。
这个高能态能够吸收输入光的辐射能量，从而使得掺镱光纤中的镱离子获得一定的能量。
在饱和阶段，当掺镱光纤中的镱离子在高能态时，它们可以通过非辐射跃迁的方式跃迁到一个低能态，当他们从高能态跃迁到低能态时，就释放出了能量，放大输入光。
在发射阶段，当掺镱光纤中的镱离子从高能态跃迁到低能态时，会释放出能量，激发产生的能量会与输入的光线叠加在一起，使得输出光能够以较高的能量进行发射。
这里的掺镱光纤激光器利用了激活离子镱离子的特性，实现了激光器的抽运、激化和能量输出。
在掺镱光纤激光器的应用中，其主要优点就是能够满足高功率、高效率、高光质、可调谐性等特殊需求。
同时，在生物医学、材料加工等领域中也有着广泛的应用。
例如，在材料加工方面，掺镱光纤激光器可用于切割、钻孔、雕刻和焊接各种材料。
在生物医学方面，掺镱光纤激光器可用于激光治疗和医学成像等领域。
总之，掺镱光纤激光器是一种非常有用的激光器，它可以产生高质量的激光输出，并可满足各种复杂的工业和医学应用。
其工作原理简单清晰，但是需要注意的是，较高的泵浦功率和较长的光纤长度会导致离子之间过多相互作用，因而降低激发和放大效率，导致激光器性能下降。
因此，在实际应用过程中，需要科学合理地制定掺杂浓度、泵浦功率与光纤长度等参数以达到最佳效果。
掺铥光纤激光器
16High-Power Pulsed 2-μm Tm3+-DopedFiber LaserYulong Tang and Jianqiu Xu Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics,Shanghai Jiao Tong University, Shanghai,China1. Introduction1.1 Research backgroundLaser beam in the 2~3μm spectral range has wide applications. It is a good candidate in laser microsurgery due to high absorption of water in this spectral region. It can also be used in environment monitoring, LIDAR, as optical-parametric-oscillation (OPO) pump sources, and so on [1-4].Tm3+-doped fiber is very suitable for producing ~2-μm laser emission due to its several unique advantages. First, Tm3+-doped fiber has a strong absorption spectrum that has good overlap with the emission spectrum of commercially available AlGaAs laser diodes. Second, the specific energy-level structure of Tm3+ ions provides the Tm3+-doped fiber laser (TDFL) quantum efficiency close to two through the cross relaxation (CR) process. Thirdly, the Tm3+-doped fiber has a very broad emission band (~400 nm), offering great wavelength tunability for the fiber laser.For achieving high-power output, Tm3+ ions are often doped into silica glass fiber to construct 2-μm fiber lasers. The silicate glass fiber has maximum phonon energy as large as 1100 cm-1 (compared to 550 cm-1 for fluorides) [5], which limits its infrared transparency wavelength less than 2.2 μm.In the past, the fiber laser was usually core pumped. Small fiber core area (<100 μm2) requires high brightness of the pump beam, greatly limiting the pump power than can be launched into the fiber core. With the advent of double-clad fiber configuration, the pumping area was changed to the cladding area (>10000 μm2), significantly facilitating pump-power launching. From then on, the output power of fiber lasers has been greatly enhanced.For fiber laser oscillation, the simplest (commonly adopted) laser resonator is defined as Fabry-Perot resonator, which is shown in Fig. 1. The pump light is launched into the fiber through a dichroic mirror, high transmissive for pump beam but high reflective for laser light. Laser oscillation forms between this dichroic mirror and the distal-end fiber facet (~4% Fresnel reflection).288Semiconductor Laser Diode Technology and ApplicationsFig. 1. The Fabry-Perot Tm3+-doped fiber laser resonator.The simplified energy-level diagram of Tm3+ ions is shown in Fig. 2. The pump light at ~790 nm excites Tm3+ ions from 3H6 to 3H4, which then nonradiatively decay to the upper laser level of 3F4 with a fluorescence lifetime of 0.55 ms [6]. The transition from 3F4→3H6 will radiate photons at wavelength of ~2 μm. Due to large Stark splitting of the energy levels, the TDFL is a quasi-four-level system.Fig. 2. The simplified energy-level diagram of Tm3+ ions.The Tm3+ ion has fluent energy levels, providing complex energy-transfer processes. The CR process (3H4+3H6→3F4+3F4), as shown in Fig 3, is very beneficial for improving slope efficiency of the TDFL. With the help of this process, high quantum-efficiency TDFLs have been realized [7-8], and the slope efficiency has surpassed 60% [9-10].For high-power ~2μm TDFLs, 790-nm AlGaAs diode lasers are preferred pump sources. This pump wavelength is the only appropriate wavelength to stimulate the beneficial CR process for TDFLs. Aside from 790 nm, laser sources at other wavelengths can also be used as the pump source, including Nd:YAG lasers (1.064 and 1.319 μm), Yb-doped fiber lasers (1.09 μm), Er3+-doped fiber lasers (1.57μm), and so on.High-Power Pulsed 2-μm Tm3+-Doped Fiber Laser 289Fig. 3. Cross relaxation between Tm3+ ions.1.2 Recent development of Tm3+-doped fiber laserThe first ~2μm TDFL was achieved by Hanna et al. in 1988 with a 797-nm dye laser as the pump source [11]. With the advent of AlGaAs diode lasers as the pump source, the all-solid-state Tm3+-doped silica [12] and fluoride [13] fiber lasers were both realized in 1990.High-power TDFLs had not been achieved until the invention of double-clad pumping configuration by Snitzer et al. in 1989. The first high-power TDFL was reported by Jackson in 1998, with maximum output of 5.4 W and slope efficiency of 31% [14]. In 2000, Hanna et al. [15] improved the output power of the TDFL to 14 W with a slope efficiency of 46%. In 2002, the 2-μm TDFL has achieved an output power of 85 W by Jackson et al. [16], the slope efficiency being 56%. At nearly the same time, 75 W 2-μm laser output was also realized in an Yb-Tm codoped fiber laser [17], where Yb3+ ions were used as sensitizers to facilitate pumping with 976-nm diodes. However, the slope efficiency was just 32% due to the lack of the “cross relaxation” process. In 2007, G. Frith reported a TDFL with output power of 263 W and slope efficiency of 59% [18]. In 2009, the 2 μm output power from the TDFL was significantly enhanced to 885W with a slope efficiency of 49.2% [19], and exceeded one kilowatt [20] just one year later. At present, single frequency output has also been over 600 watts [21]. These significant developments in 2-μm TDFLs have made them a much attractive tool in many application areas.Along with the power scaling of continuous-wave (CW) TDFLs, many works have also been carried out to realize high-peak-power or short-pulse-duration TDFLs. The first 2-μm Q-switched TDFL was carried out in 1993 with an acousto-optic (AO) modulator [22]. The pulse width was 130 ns, and the peak power was only 4 W. In 1995, 2-μm femtosecond (500 fs) laser pulse was first achieved in Tm fiber [23]. By also using AO modulator, a peak power of 4 kW (with pulse width of 150ns) TDFL was realized in 2003 [24], but the average power was just 60 mW. In 2005, by adopting an amplification configuration, the peak power of 2μm Tm fiber laser has reached 230 kW (108 fs) with improved average power to 3.1 W [25]. For achieving high pulse energy from TDFLs, the gain-switching technique is usually employed. In 2000, 2-μm TDFL has achieved 10.1-mJ pulse energy [26], which was further improved to 14.7 mJ in 2005 [27]. These gain-switching TDFLs were often accompanied by290Semiconductor Laser Diode Technology and Applications relaxation spikes, showing comparatively low system stability. Recently, special measures (such as employing high pump ratio or combined gain-switching and amplification) have been applied to scale the averaged 2-μm pulsed laser power to tens of and even hundred watt levels [28–32].2. High power acousto-optic Q-switching Tm3+-doped fiber laserNowadays, high-average-power 2-μm pulsed laser are eagerly required in pumping 3~4-μm mid-infrared lasers [33], environmental detecting [34], and medical surgery. For 2-μm TDFLs, pulsed operation can be realized through either Q-switching or mode-locking. Q-switching can usually provide a somewhat higher average power, but mode-locking operation can often provide much narrower pulse width thus higher pulse peak power. In this section, we mainly introduce AO Q-switching operation of TDFLs for achieving high-power 2-μm laser pulses in our laboratory.2.1 Power scalability of pulsed Tm3+-doped fiber laserIn our experiment, the double-clad Tm3+ silica fibers have a Tm3+ concentration of ~2wt.%. The fiber core has a diameter of ~30-µm and a numerical aperture (NA) of 0.09. The pure-silica inner cladding is D-shape, and has a 400-µm diameter and a NA of 0.46. The absorption coefficient of the fiber at the pump wavelength (~793 nm) is about 3 dB/m.The experimental setup for the AO Q-switched TDFL is shown in Fig. 4. The pump source was a pig-tailed high-power laser diode (LD) operated at 793 nm with a total output power of ~110 W. The pig-tail fiber has a diameter of 200 µm and an NA of 0.22. Two aspheric lenses were used to couple the pump light into the fiber, with a coupling efficiency of ~90%. A dichroic mirror (T=97%@793nm&R=99.5%@2µm at 45° coating) was employed to transmit the pump light and extract the 2-µm laser beam. A high-reflection mirror (R=99.5%@2000nm) at the far end is used to provide the laser light feedback, which together with the perpendicularly cleaved pump-end fiber facet (~3.55% Fresnel reflection for laser oscillation) complete the laser cavity. The Tm3+-doped gain fiber is wrapped on a copper drum or immerged in water for cooling. At both fiber ends, a short piece of gain fiber (with the polymer coating removed) is placed between a copper heat sink for efficient heat cooling. At the output end of the fiber, another dichroic (T=98%@2µm&R=99.8%@793nm) is used to filter the residual 793-nm pump power. The AO Q switch is inserted between the far fiber end and the high-reflection mirror. The far end fiber is angle-cleaved (~8°) to avoid the parasitic oscillation due to fiber-facet reflection. The laser output power was measured with a thermal power meter and the laser spectrum was tested with a spectrometer.Figure 5 shows the average output power of the Q-switched TDFL with respect to the 793-nm launched pump power at the repetition rate (RR) of 50 kHz. The maximum laser power was ~32 W with a slope efficiency of 36%. At high power level, the AO switch could not switch off completely, leading to decreased signal-to-noise ratios. This is an important issue that should be addressed in high-power pulsed fiber lasers. The inset of the figure shows the laser spectrum that measured at the output power of 30 W. The emission wavelength was centered at 2017 nm with a FWHM (full width at half maximum) width of ~11 nm. This spectrum includes many peaks, showing that many longitudinal modes have oscillated in the cavity.High-Power Pulsed 2-μm Tm3+-Doped Fiber Laser 291Fig. 4. Experimental setup for the AO Q-switched TDFL.As shown in Fig. 5, the output power shows a linear dependence on the pump power at the high RR (50 kHz). However, at lower RRs, such as 10 kHz, the output power curve shows a severe deviation from linearity (not shown here), i.e., there is a rollover of the output power curve. This rollover indicates that strong ASE was generated in the fiber and was emitted from both fiber ends. In order to achieve linear power dependence at lower RRs, such as 10 kHz, high diffraction-efficiency AO modulators are required. The appearance of ASE also put a limit on the maximum pulse energy that can be obtained in Q-switched fiber lasers. Further increasing the pump power just improves the ASE, and the Q-switched operation will become less effective.Fig. 5. Average output of the 6-m AO Q-switched TDFL.Inset is the laser spectrum measured at the 30-W output level.In pulsed fiber lasers, the RR usually has influence on the average output power when pump power is fixed. We measured the average power of the 6-m TDFL at a constant pump lever (50 W pump power) under different modulation frequencies, and the results are292Semiconductor Laser Diode Technology and Applications shown in Fig. 6. The maximum output power only shows little decrease when the RR decreases from 50 kHz to 20 kHz. However, when the RR further decreases to less than 20 kHz, the average power indicates a significant drop (over 20%). Therefore, the AO modulation frequency only has significant impact on the Q-switched TDFL when it is operated at low RRs. The pulse train recorded under the RR of 10 kHz is shown in Fig. 7, indicating somewhat low inter-pulse instability.Fig. 6. Average output of the 6-m AO Q-switched TDFL under constant pump power but different RRs.Fig. 7. Pulse train of the 6-m AO Q-switched TDFL at the RR of 10 kHz.Operated under the RR of 10 kHz, the recorded pulse shape under different pump levels are shown in Fig. 8, where Pt denotes the threshold pump power. Just at the threshold, the laser pulse has a smooth shape with a pulse FWHM width of 240 ns. With increasing pump power, the pulse width narrows, and multiple peaks appears in the pulse. In a review description, Wang et al. proposed that the multi-peak pulse was initiated from the injectionHigh-Power Pulsed 2-μm Tm 3+-Doped Fiber Laser 293 of ASE by quick switching of the AO modulator and the subsequent evolution of the switching-induced perturbation [35].Fig. 8. Pulse evolution of the fiber laser at 10 kHz under different pump levels.2.2 Pulse narrowing of Tm 3+-doped fiber lasersFor Q switched fiber lasers, the laser pulse width can be expressed as [36] 0()21ln p r r L r r c ητδ=×−−, (1) where, δ0 is the single-pass cavity loss, η(r ) is the energy extraction efficiency, r is the pump ratio (the ratio of the pump power to the threshold power), and L is the cavity optical length. Equation (1) implies that we can narrow the pulse duration through either increasing the pump strength r or shortening the fiber length. Simple calculations of the influence of the pump ratio on pulse narrowing are shown in Figs. 9 and 10, where 1ln r A r r=−− corresponding to the pulse width parameter. As shown in Fig. 9, the pulse width can be narrowed by a factor of ~6.3/1.5=4.2 when the pump ratio is increased from 2 to 10. When the pump ratio is over 10, further increasing the pump strength, such as from 10 to 100 (Fig.10), can hardly shorten the pulse width to a appreciate level.Based on the above analysis, we made an effort to obtain 2-μm laser pulse as narrow as possible from an AO Q-switched TDFL. For this aim, we shortened the fiber length to 0.4 m and increased the pump ratio as high as possible to carry out the Q-switching operation of the TDFL. With this fiber length, the maximum average output power was less than 2 W due to the fiber-length induced limited pump absorption. At a constant RR of 10 kHz, the pulse width narrowing characteristic with absorbed pump power is shown in Fig. 11. With increasing pump power, the pulse width reduces significantly. However, when the pump power was larger than 14 W, further increasing pump cannot lead to pulse narrowing. The shortest pulse width achieved with this 0.4-m TDFL was ~48 ns, as shown in the inset of Fig. 11.Semiconductor Laser Diode Technology and Applications 294Fig. 9. Simulated evolution of the pulse width narrowing factor as a function of pump ratio from 2 to 10.Fig. 10. Simulated evolution of the pulse width narrowing factor as a function of pump ratio from 10 to 100.Pump ratio rA Pump ratio r AHigh-Power Pulsed 2-μm Tm3+-Doped Fiber Laser 295Fig. 11. Pulse width of the 0.4-m TDFL as a function of the absorbed pump.Inset is the pulse shape with a width of ~48 ns.Compared with bulk pulsed lasers, pulsed fiber lasers can provide higher average power due to their intrinsic high gain. However, it is still difficult to construct high-power 2-μm pulsed TDFLs at present. The difficulties mainly lie in the low damage threshold of the facets of fiber ends or other optical elements, and the onset of ASE. Therefore, how to improve the damage threshold of related optical components and efficiently suppress ASE will be the key problems for achieving high-power pulsed 2-μm TDFLs.3. Gain-switching operation of Tm3+-doped fiber laser3.1 High-power gain-switching 2-µm fiber laserWith active Q-switching crystal lasers, stably controlled pulsed laser output can be achieved. With fiber amplifying systems, high gain can be easily obtained. Therefore, combining these two techniques is a potential way to scale 2-µm pulsed laser power to a new level. Besides, the advantages of high-doping concentration, efficient pump absorption, and long exited-state lifetime of Tm3+ fibers provide excellent prerequisites to achieve high-power pulsed 2-µm laser output.In conventional fiber amplifiers, the seed source power is usually low. With such kind of seed source, a multi-stage fiber amplifier system must be constructed to achieve high average output power. The whole system is thus complicated and expensive. When the seed source has a narrow linewidth, the amplified output power of the fiber amplifier will be limited by the onset of stimulated Brillouin scattering (SBS). Ch. Ye et al. proposed using self-phase modulation (SPM) induced linewidth broadening to suppress SBS, and have obtained 50-W average power from a fiber amplifier [37]. For amplification of broad band ~2-µm laser pulses in Tm3+ fibers (~20 nm), SBS suppression is not a serious issue.296Semiconductor Laser Diode Technology and Applications For obtaining 2-μm laser pulse, gain-switched fiber lasers can be excellent candidates owing to the well controlled pump pulse width and various available pump wavelengths. Gain-switched operation of TDFLs has achieved pulse energy of more than 10 mJ [38-40] and pulse width as narrow as 10 ns [41]. Compared with fiber amplifier systems, gain-switched devices can provide a more compact system configuration.At present, actively Q-switched crystal lasers can provide moderate-power (several watts) 2-μm laser pulse with stably controlled characteristics. At the same time, TDFLs can provide high operation efficiency by taking advantage of the CR process [42-44]. Here, we will investigate how to improve the output from the pulsed TDFL through combining a high-power seed source with large-mode-area Tm3+ fiber amplification.In experiment, we used a high-power Tm:YLF laser to gain switch the TDFL, which in turn was pumped by 793-nm LDs. This gain-switched system is different from conventional fiber amplifiers in that the high-power ‘seed’ laser acts just as a pulse switch, while the spectral characteristics are decided by the gain fiber. It is also different from conventional gain-switched lasers in that the gain and the switch are separated. We defined this laser system a combined gain-switched fiber laser (CGSFL) system. With this system, we will show how to achieve high-power 2-μm pulsed laser output through the combination of high-power switch laser, damage-threshold improvement of the fiber-end facts, and appropriate system configurations.The experiment setup for the CGSFL system is shown in Fig. 12 [32]. The switch laser was an AO Q-switched Tm:YLF slab laser (pumped by a 793-nm LD) with the laser wavelength at 1914 nm. The Tm:YLF laser can provide a maximum average output power of ~4.4 W and RR from 500 Hz to 50 kHz. The pulse width can be varied between ~80 ns and ~1.2 μs by tuning the RR together with pump power. The 1914-nm laser pulse from the Tm:YLF laser was launched into the Tm fiber to switch the TDFL. The Tm3+-doped silica fibers (both in the first-stage and the second-stage) had a ~25-µm diameter, 0.1-NA core doped with ~2wt.% Tm3+. The octagonal pure-silica inner cladding had a 400-µm diameter and a NA of 0.46.In the first-stage CGSFL, the pump source was a 120-W LD module at 793 nm. Two aspheric lenses (L1) were used to couple the 793-nm pump light into the gain fiber, with a coupling efficiency of ~80%. In this stage, a 6-m Tm3+ fiber was adopted with total pump absorption of ~18 dB. The amplified laser beam from the first stage was then launched into the second-stage Tm3+ gain fiber for further power scaling. In the second stage, the pump source was a ~230-W 793-nm LD module. The Tm3+ fibers were wrapped on 10-cm-diameter copper drums, which in turn were cooled by 18-°C circulating water.In the first-stage CGSFL system, we launched ~1-W switch laser beam (with a pulse width of ~400 ns) into the fiber and kept the RR at 10 kHz. Under maximum pump power, this amplification stage can provide a maximum 2-μm pulsed laser of ~40 W with a slope efficiency of 50%. The maximum pulse energy was about 4 mJ, corresponding to a peak power of ~10 kW. At this level, no fiber facet damage was observed.For amplification in the second stage (4-m Tm3+ fiber), the output of the first stage was kept at 15 W and the pulse RR was kept at 50 kHz. The laser output characteristics from thesecond stage Tm3+ fiber are shown in Fig. 13 [32]. The maximum output is ~105 W (pulse energy of 2.1 mJ) with a slope efficiency of 52.8%. When we decreased the RR to 40 kHz, the output power dropped down to ~100 W (corresponding to pulse energy of 2.5 mJ), and the fiber end facet was damaged. At this time, the pulse width was measured to be ~600 ns, leading to pulse peak power of ~4.2 kW.Fig. 12. Experimental setup of the combined gain-switched Tm3+-fiber laser.LD: laser diode; AR: anti-reflection; HR: high reflection; AO: acousto-optic;L1: aspheric lens with f=11 mm; L2: convex lens with f=40 mm; M1& M2: dichroic mirrors.In order to obtain higher output laser pulse energy, we fusion spliced a short piece (~2 mm) of passive silica fiber (1-mm diameter) to both ends of the active Tm fiber. At this time, only the first-stage CGSFL system (6-m fiber) was employed. We decreased the pulse RR to 500 Hz and kept the seed power at 200 mW. The maximum amplified ~2-μm output power was ~5.2 W, corresponding to a pulse energy of 10.4 mJ. The 1-mm-diameter endcaps greatly decreased the optical fluence at the output facet (<5 J/cm2), which is less than the measured surface-damage fluence for nanosecond pulses in silica [45]. According to the empirical damage threshold for fused silica [46] of >22t P0.4 J/cm2 (t P is the pulse width in ns), the damage threshold of the 1-mm endcap facet would be hundreds of mJ. Therefore, this CGSFL system has the potential to scale the ~2-μm pulse energy even higher.Fig. 13. Amplified output power from the two-stage CGSFL system at 50 kHz.Under different RRs, the maximum average power and pulse energy achieved with this CGSFL system are shown in Fig. 14 [32]. The maximum output power increases near linearly with RR. Over 40 kHz, the roll-over of the average output was owing to the limited pump. On the other hand, the maximum pulse energy first decreases sharply with RR and then almost saturates due to limited stored energy. The inset is the pulse shape measured at the pulse energy of ~10 mJ with a FWHM width of 75 ns, corresponding to a peak power of ~138 kW.M a x i m u m p u l s e e n e r g y (m J )M a x i m u m o u t p u t p o w e r (W )Repetition rate (kHz)Fig. 14. Maximum average output power and pulse energy of the CGSFL system as a function of RR.With the two-stage CGSFL system, the evolution of the 2-μm pulse shape (50 kHz) is shown in Fig. 15 [32]. The switch laser was kept at 1 W and had a pulse width of 900 ns. Withincrease of output power, the pulse width increased first and then narrowed, accompanied by steepening of the pulse leading edge. At 100-W power level, the pulse width was reduced to 750 ns, corresponding to pulse narrowing of ~17%. The pulse broadening at low power levels was probably originated from coexistence of the switch pulse and the ~2020-nm laser pulse (see Fig. 16). The pulse width narrowing and pulse steepening at high power levels was attributed to gain saturation and self-phase modulation [47-49].Fig. 15. Characteristics of the switch pulse and the fiber laser pulse at different power levels.(a)-(d) were measured after the first-stage CGSFL and (e) was measured after the second-stage CGSFL.Under the same operating conditions (50-kHz RR and 1-W seed power), the spectrum of the seed and the output pulse at various power levels are indicated in Fig. 16 [32]. The fluorescence spectrum of the Tm3+-doped fiber is also shown in Fig. 16(a). It is clear that the 1914-nm seed laser was amplified at comparatively low power levels. When the 1914-nm laser was near 5 W, the ~2-µm laser pulse was stimulated, and thereafter more and more stored energy was extracted by the 2020-nm laser pulse. Finally, all energy was included in the 2020-nm laser beam. This is a unique characteristic of the CGSFL system, significantly different from fiber amplifiers and singly gain-switched devices. The detailed process can be described as follows. Owing to the broad fluorescence spectrum of our Tm fiber (1920-2040 nm), the switch pulse (1914 nm) lies in the wing of the gain spectrum. When the switch laser was launched into the fiber core, more than 90% of the laser was absorbed. At the same time, the Tm fiber accumulated population inversion through 793-nm pumping. The unabsorbed 1914-nm laser pulse will be amplified, while the absorbed 1914-nm laser pulse will modulate the gain of the system and act as a switch for the ~2-µm laser. Gain competition between the 1914-nm amplification and the stimulation of the ~2-µm laser emission leads to the evolution of the spectrum. Eventually, the 1914-nm laser was consumed completely and all stored energy was extracted by the ~2-µm laser emission. At 100-W level, the spectral width of the ~2-µm laser pulse was ~25 nm. We also observed the spectral evolution of a 2-m Tm3+ fiber laser with one-stage CGSFL configuration, and found that shorter fibers need stronger pump to switch on the CGSFL system.Fig. 16. Laser spectra (blue line) of the switch pulse (a), and that of the fiber laser pulse (b-f) at different power levels of the CGSFL system. (a) also shows the fluorescence spectrum of the Tm fiber.3.2 Resonant-pumping 2-µm fiber laserIn high-power ~2-μm fiber lasers, the pump source is usually 790-nm LDs. Great difference between the pump wavelength and the laser wavelength causes a high quantum defect. This makes the optical-optical transfer efficiency of TDFLs be generally lower than that of high-power Yb fiber lasers. In order to improve the quantum efficiency thus the slope efficiency of high-power TDFLs, the pump wavelength must be elongated toward the laser wavelength. Such a pumping scheme with the pump wavelength approaching the laser wavelength is defined as resonant pumping. Resonant pumping TDFLs with ~1.6-µm wavelength has achieved slope efficiencies of ~80% with tens of miliwatts output [50].In the pulsed 2-µm TDFLs achieved either by Q-switching [24] or by mode-locking [51], the laser power and pulse energy were usually limited. We have shown in the previous section that gain-switched TDFLs can produce high pulse energies, but their slope efficiencies were still low. Besides, the output pulses of these gain-switched TDFLs consist of a series of relaxation spikes, showing great chaotic temporal characteristics. In order to eliminate the chaotic spiking in gain-switched fiber laser, we must adopt highly-resonant pulsed pumping scheme, which is named as fast gain switching [52].The experimental setup for the fast gain-switched TDFL is shown in Fig. 17 [53]. The pump source was an AO Q-switched Tm:YLF laser with 8.5-W maximum output at 1.914 µm. The M2 beam quality of the pump beam was ~2. The double-clad Tm3+-doped silica fiber had a ~30-µm diameter, 0.09 NA (numerical aperture) core doped with Tm3+ of ~2wt.% concentration. The pure-silica D-shape inner cladding had an average diameter of 400 µmand a NA of 0.46. One aspheric lens (f = 11 mm) was used to couple the pump light into the fiber core, with a coupling efficiency of ~90%. The absorption coefficient of the Tm3+ fiber at the pump wavelength (1914 nm) was measured with the cut-back method to be ~3 dB/m. At the output fiber end, a dichroic mirror (R=90%@1914nm & T=75%@1940nm, 45° coated) was used to filter the un-absorbed 1914-nm pump light. The 1940-nm laser output was calibrated by subtracting the un-filtered pump light and incorporating the filter-mirror-rejected laser light.Fig. 17. Experimental setup of the resonantly gain-switched TDFL. HT: high transmission; HR: high reflection.In experiment, three fiber lengths of 2, 4, and 6 m were used. Pumping at 1914 nm directly excites the Tm3+ ions from the ground state 3H6 to the upper laser level 3F4, which has a lifetime of ~340 µs [10]. The comparatively long lifetime of the upper laser level and the quasi-three-level nature of the laser transition guarantee efficient operation of the system through resonant pumping.Fig. 18. CW Output performance of the resonantly-pumped TDFL.Inset shows the laser spectra of the output laser beam and the pump light.。
掺铒光纤激光器(EDFL)的原理与应用简介
掺铒光纤激光器（ＥＤＦＬ）的原理与应用简介 光信０３０４班 杨鹤猛 指导教师 王英 摘要： 本文从增益介质，谐振腔结构和泵浦源三个构成激光器的必要条件出发，重点介绍了掺铒光纤激光器—ＥＤＦＬ的原理，接着简要介绍了光纤激光器的特点及分类，最后结合掺铒光纤激光器的特点阐明其应用并做了总结。
关键字：光通信 光纤激光器 掺铒光纤激光器 环形腔 １．引言 掺铒光纤激光器简称ＥＤＦＬ（Ｅｒｂｉｕｍ Ｄｏｐｅｄ Ｆｉｂｅｒ Ｌａｓｅｒ），光纤激光器的一种，是在掺铒光纤放大器（ＥＤＦＡ）技术基础上发展起来的。
早在１９６１年，美国光学公司的Ｅ．Ｓｎｉｔｚｅｒ等就在光纤激光器领域进行了开创性的工作，但由于相关条件的限制，其实验进展相对缓慢。
而８０年代英国Ｓｏｕｔｈｈａｍｐｔｏｎ大学的Ｓ．Ｂ．Ｐｏｏｌｅ等用ＭＣＶＤ法制成了低损耗的掺铒光纤，从而为光纤激光器带来了新的前景。
近期，随着光纤通信系统的广泛应用和发展，超快速光电子学、非线性光学、光传感等各种领域应用的研究已得到日益重视。
其中，以光纤作基质的光纤激光器，在降低阈值、振荡波长范围、波长可调谐性能等方面，已明显取得进步，是目前光通信领域的新兴技术，它可以用于现有的通信系统，使之支持更高的传输速度，是未来高码率密集波分复用系统和未来相干光通信的基础。
目前光纤激光器技术是研究的热点技术之一。
ＥＤＦＬ利用光纤成栅技术把掺铒光纤相隔一定长度的两处写入光栅，两光栅之间相当于谐振腔，用９８０ｎｍ或１４８０ｎｍ泵浦激光激发，铒离子就会产生增益放大。
由于光栅的选频作用，谐振腔只能反馈某一特定波长的光，输出单频激光，再经过光隔离器即能输出线宽窄、功率高和噪声低的激光。
２．ＥＤＦＬ的工作原理 （１） ＥＤＦＬ的增益介质—ＥＤＦ ＥＤＦ作为ＥＤＦＬ的增益介质，其基本原理是在光纤的纤芯中能产生激光的稀有元素（如铒、钕、镨等），通过激光器提供的直流光激励，使通过的光信号得到放大。
利用掺铒光纤的非线性效应，把泵浦光输入到掺铒光纤中，使光线中的铒原子的电子能级升高。
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掺铥光纤激光器
1、掺铥光纤激光器
掺铥光纤激光器的光谱可调谐范围更宽（~1600 nm-2200 nm），该波段处于人眼安全波段且包含了1940 nm附近的水吸收峰，对组织的穿透深度浅，且还包含几个大气窗口及特殊气体的吸收峰。
与同时处于人眼安全波段掺铒或铒镱共掺1550 nm激光器相比，掺铥光纤激光器的光光转换效率可达60%以上；且位于铥离子吸收带的790 nm半导体激光器技术成熟，可提供高功率泵浦源；此外，此波段泵浦时，量子转换效率为200%。
掺铥基质为石英光纤，也容易实现高功率输出。
对于掺铥光纤激光器的研究，连续输出已达千瓦量级，如：飞秒150 W的功率输出，皮秒也达到百瓦的输出功率水平，相比之下，单脉冲能量较高的纳秒量级脉冲输出平均功率较低，且多数为空间泵浦结构，最高仅为110 W。
793 nm 半导体泵浦激光器的输出功率已达数百瓦，所以掺铥光纤激光器的输出功率可更高。
且与掺镱光纤激光器相比，掺铥光纤激光的受激布里渊散射和受激拉曼散射的产生阈值要高4倍以上，光纤端面的损伤阈值也高出近10倍，在高功率输出方面优势更加明显。
目前高功率、可调谐掺铥光纤激光器正处于研究的热点。
2、研究进展
(1)、纳秒脉冲掺铥光纤激光器研究进展（主动调Q）：
输出参数
（脉冲能量/功率、斜率效率/重频、脉宽）
是否
全光纤结构
研究单位
4 W，4 kHz，130 ns 否加拿大信息技术研究12.3 W，100 kHz，4
5 ns 否法德研究所
33 W，13.9 kHz，15 ns 否耶拿大学应用物理研究所52 W，50 kHz，822 ns 是新加坡南洋理工大学
(2)、皮秒/飞秒脉冲掺铥光纤激光器研究进展（锁模）：
平均功率，重复频率，脉宽，实现方式
是否
全光纤结构
研究单位
3.1 W，100 MHz，108 fs，CPA 否美国IMRA公司5.4 W，100 kHz，300 fs，SESAM/CPA 是美国PolarOnyx公司
7 W，2 MHz，33 ps，电流调制否英国南安普顿大学
152 W，49.1MHz，~700 fs，CPA 否德国耶拿大学。