高脉冲重复频率调QTHoGdVO4激光器_英文_

I第17卷增刊强激光与粒子束Vol.17,No.S0 2005年4月H IGH POWER LASER AND PARTICLE BEAM S A pr.,2005

Article ID:1001-4322(2005)S0-0029-04

Q-switched Tm,Ho:GdVO4laser with

high pulse repetition frequency*

YA O Bao-quan,JU You-lun,WAN G Yue-zhu,H E Wan-jun

(N ational K e y L aborator y of Tuna ble L ase r Te chnolog y,H ar bin In stitute of Te chnolog y,H ar bin150001,China)

Abstract:CW and Q-sw itched operat ion o f T m,Ho:G dV O4laser is r epo rted in this paper.T he T m,H o: GdV O4cry stal is coo led by liquid nitro gen and end-pumped by a laser diode of793nm.O utput pow er of4.0W

and optica-l to-o ptica l efficiency of26%is achiev ed at CW mo de.With aco usto-optically Q-sw itched operatio n,

an av erag e po wer3.9W o f at a pulse-r epetit ion rate of10kHz with pulse dur atio n of50ns is o bt ained.T he

pulse w idth is t unable f rom23ns to50ns by chang ing r f(r adio fr equency)o ff-time of AO Q-sw itch.At a pulse-

repetition rate of10kH z,0.39mJ o f pulse energ y,and7.8kW o f peak pow er w ere measur ed

Key words:Dio de laser;End-pum p;AO Q-swit ch;T m,H o:GdV O4

C LC number:T N248Document code:A

T he int erest in al-l solid-state laser operat ing in the ey e-safe spectral r egion near2L m is well acknow ledg ed for medica l and r e-mo te-sensing applications[1,2].Since the first demonstrat ion o f rar e-earth laser o per ation in YA G obtained at cry og enic temper a-tur e,co nsider able pro gr ess has been made.A t present,ro om-temperature,diode-pumped2L m laser(co nt inuous and Q-sw itched)[3]is integr ated in systems fo r g round-based or airbor ne lidar measurements.A dditio nal applications for w hich shor t du-r atio n o ptica l pulses at2L m ar e r equired include altimetr y,topog raphical,and nonlinea r o pt ical studies.T m,Ho codoped lasers are co nducive to operatio n in Q-sw itched mode due to their10ms fluorescence lifet ime com par ed to230L s in neo dy mium doped Y AG. Ho wever,in many ho sts studied to date upco nv ersio n there is a deleter ious influence,manifest ing as an effect ive lifet ime r educ-t ion,w ith concomitant r eduction of the energ y stor age capacity and loss of co nv ersion efficiency[4].

T he abso rption cro ss sectio n of thulium in GdV O4is co nsider ably stro ng er and br oader(770~820nm)than that in YA G and YL F,and the spectrum shifts closer to the emissio n wav elength of co mmercially av ailable A lG aA s laser diodes.In this exper-i ment,a794nm laser dio de was used as the pumping so ur ce.P rev ious r esults w ith Y L F cr ystals in prev ious ex periments have show n fracture w hen subjected t o pump densities gr eater than5kW/cm2.GdV O4host has g ood therma-l mechanical pro per ty and can ex per ience pum p densit y g reater than12kW/cm2,w hich is co nfirmed by o ur experiment,allow ing to scale up holmium laser averag e pow er by end-pum ping fabr ication without the requirement o f diffusion bo nded composit e r od.T he Boltzmann co upling l-i fetime of thulium3F4and ho lmium5I7in GdVO4host is3ms,that is shor ter than9ms fo r T m:H o:YA G and15ms f or T m:Ho: YL F.Sho rt lifetime and larg e emissio n cross sectio n are ver y favor able fo r the Q-swit ched short pulse g ener ation operated at repe-t itio n r ate up to10kH z.

Wo rk by M o rr is et al[5]demonst rated the generation o f co ntinuous w ave4.6mW o utput at2.048L m w ith135mW abso rbed pump po wer in T m:Ho:GdV O4.T he slope efficiency of10%in T m:GdVO4laser pumped by a laser dio de w as achiev ed by M ikhailo v et al[6].W yss also demo nstr ated1.4W r adiat ion at1.95L m w ith32W laser dio de pumping[7].Higher peak pow er pulse w ith sho rter pulse w idth and stable pulse t rain was o btained fro m T m,H o:GdV O4laser in our ex periment.

1Experimental setup

The T m,H o:GdVO4cr ystal is end-pumped by fiber-coupled laser diode arrays w hich deliver m ax imum 14.8W content w ithin fiber co re of0.4m m and numerical value of0.3.The pumping lig ht is temperatur e tuned to794nm for o ptimal absor ption and uniform therm al distr ibution in T m,H o:GdVO4cry stal,and refocused into crystalw ith beam diam eter of approx im ately0.6mm for optim um ov er lap betw een the pump beam and the laser beam.T he input mirr or w as a plane m ir ror w ith an antireflection coating at794nm on the incident

*Received date:2004-11-22;Revised date:2005-03-30

Fou ndation item:Su pported by th e Scientific Res earch Foundation of H arbin In stitute of T ech nolog(HIT200214)

Biography:Yao Baoquan(1970)),male,Ph.D,as sociate profes sor,en gaged in solid state laser and n on linear frequency conversion;E-mail:bqyao@。