二极管泵浦被动调QNd_YAG_KTP绿光激光器_英文_

第31卷第1期 光子学报 V ol.31N o.1 2002年1月 ACT A PHOTONICA SINICA Januar y2002　LD-PUMPED PASSIVELY Q-SWITCHEDNd∶YAG/KTP GREEN LASERZheng Quan1,Zhao Ling21Changchun I nstitute of Op tics,Fine M echanics and Phy sics,CA S,Changcun1300222Shanghai I nstitute of Op tics and Fine M echanics,CA S,Shanghai201800 Abstract　An LD-pumped Nd∶YAG/KT P/Cr∶YAG passively Q-sw itched high r epetition rate green laser w as reported in this paper.With750mW incident pum p laser,Q-sw itched gr een laser w ith av erag e po wer of38mW,pulse w idth o f14.7ns,repetitio n rate of20.4kHz and peak pow er of126.6W w as o btained.Keywords　LD-pumped;Nd∶YAG;Passive Q-sw itching;Gr een laser0　Introduction In recent y ears,g reat attention has been paid to Q-sw itched all-solid-state blue-g reen laser for som e applicatio ns,such as spec-tr oscopy,display,optical data sto rage,undersea co mmunicatio ns and so on.Generally,active Q-sw itch requires hig h-v oltage or RF driv er,so it is co mplicated and ex pensive.On the contr ary,pas-sive Q-sw itch is less ex pensive,smaller,mo re ro-bust,r eliable and doesn′t r equire electronics.Recently,a novel saturable abso rber Cr∶YAG used as passive Q-sw itch has received much attentio n1.Cr∶YAG,w hich demonstrates saturable absorptio n property at the w avelength range of0.9～1.2 m,has the advantages of large absorption cro ss sectio n,moder ate ex cited-state lifetim e,hig h doped-ion concentration,goo d therm al conductivity,high damag e threshold, low saturatio n intensity,no degradation w ith time,dur ability,stable physical and chem ical pr operties.So it is considered to be an ideal sat-ur able absorber as passive Q-switch for all so lid-state m iniature Nd-doped lasers to o btain high peak pow er and high repetition rate pulse.Lamp and LD pumped Q-sw itched infrared lasers with Cr∶YAG have been successfully demo nstr ated fo r Nd∶YAG,Nd∶YVO4and N d ∶YLF2～4.But the intracavity frequency dou-bling of a CW laser-diode-pum ped Cr∶YAG Q q-sw itched Nd∶YAG,Nd∶YVO4or Nd∶YLF gr een laser hasn′t been repor ted yet as far as w e kno w5,6.In this paper,by using a CW laser dio de as pump source,Cr∶YAG as passiv e Q-sw itch and KTP as intracav ity frequency-do ubling cry stal, w e have realized the Q-sw itching operation of Nd∶YAG gr een laser.1　Experimental setupFig.1sho ws the ex perimental setup of Q-sw itched g reen laser.A QW-1000laser diode made by Institute of Sem iconductor,CAS,is used as pump source;Nd∶YAG and KTP gro wn by Shandong U niversity used as lasing and fre-quency doubling cr ystals respectively;A piece of Cr∶YAG g row n by SIOM is used as passive Q-sw itch;A hig h-stability driver made by CIOM is used to offer current fo r LD and the tem perature co ntroller.T herefore,all the laser devices are made of homemade com po nents.The QW-1000LD is a continuous GaAlAsF ig.1　T he ex per imental setupSuppo rted by863plan(N o.863-307-13-02)　Receiv ed date:2001-06-11quantum-w ell laser diode w ith m ax imum pow er of1W,em issio n lig ht cross section of100×1 m2and divergent ang le o f7.8×28.6deg2.By T EC, the LD′s emitting w aveleng th is tuned to the N d ∶YAG′s absor ption peak at808.5nm to m ake Nd∶YAG fully utilize the pump light.In the ex perim ent,because laser dio de′s e-mission cross section is very small,no optical co upling system is used,nam ely,pump light is directly injected into N d∶YAG nex t closely to it.Results w ould show that even w ithout pump light shaping and fo cusing,w e can also obtain only the TEM00m ode oper ation due to the“dy-nam ic apertur e effect”o f Cr∶YAG1,w hich re-strains high-order m odes fr om oscillating.Left facet of Nd∶YAG(1.0mm thick, 1.1at%doped)is co ated w ith808nm AR and 1064nm H R as a reflectiv e mirro r o f the res-onator,and right facet with1064nm AR.Both sides of Cr∶YAG(7×7×1.4mm3,T0=87% fo r small sig nal)are coated with1064nm AR. Bo th sides of KT P(2×2×9mm3,II-ty ped phase matching)coated w ith1064/532nm AR.Left co ncave side of M( =50mm)co ated w ith 1064nm HR and532nm AR,and rig ht plane side w ith532nm AR.In o rder to obtain narrow pulse w idth,all the com po nents should be placed clo sely to r educe the resonator′s leng th.Here, the resonato r′s length is about15mm.2　ResultsBefore measuring the par am eters of532nm pulse,808nm and1064nm are filtered out by the “Filter”.A pow erm eter and a dig ital stor age o s-cillosco pe(500M Hz bandw idth)are used to measure the aver ag e pow er,peak po wer,pulse w idth and period of Q-sw itched green laser.A f-ter that,the repetition rate and sing le pulse ener-gy also could be g ot.The threshold of Q-sw itched g reen laser is abo ut270mW.W hen the incident pump laser is 750mW,the Q-sw itched green laser w ith averge po w er of38mW,pulse w idth of14.7ns,r epeti-tio n rate of20.4kHz and peak pow er of126.6W is obtained,optical to optical co nv ersion efficien-cy mo re than5%.M easurements sho w that the average pow-er,peak pow er,repetition rate and single pulse energy all g reatly increase,w hile pulse w idth slig htly decr eases w ith pump pow er increasing.These results ar e similar to Ref.6.Fig.2is the relatio nship curve o f av er ag e output pow er o f Q-sw icthed green laser as a function of incident pump pow er. F ig.2　T he relatio nship o f aver agepo wer vs.pump po werFig.3and Fig.4are the w avefo rms w itho ut and w ith KT P in the cavity,namely,the wave-fo rms of Q-sw itched1064nm and532nm respec-tiv ely.They sho w that the w avefo rm o f Q-sw itched green laser is smoother than that o f Q-sw itched IR laser due to fr equency doubling effi-ciency pro portional to the intensity o f fundamen-tal frequency w ave.T he fig ur es also show that the pulse w idth of Q-sw itched g reen laser is larg er than that of Q-sw itched IR laser because the ex istence of KT P has incr eased the pho to n′s lifetime in the cavity.F ig.3　Wav efor m of106nm pulse(20nw/div)Fig.4　W avefo rm o f532nm pulse(20ns/div)3　ConclusionBy using a CW laser diode as pump sour ce, Cr∶YAG as passive Q-sw itch,KT P as intracav-ity frequency do ubling crystal,w e have realized Q-sw itching operation of Nd∶YAG green laser. T he all-solid-state Q-sw itched green laser has611期 Zheng Q uan,et al.L D-pumped passiv ely Q-sw itched Nd∶Y AG/K T P gr een laserco mpact structure and can generate hig h r epeti-tio n rate and high peak pow er g reen pulse.In addition,the average pow er,repetition rate and peak pow er of the pulse g reen laser in-crease sharply as the pum p pow er increase. Now,w e are preparing to use a2W laser diode and a“V-shaped”folded cavity to achieve better Q-sw itched pulse gr een laser.References1　L eng Y ux in,L in Lihuang,Ou Yang bin,W an X iaoke.A bsor ption of ex cit ed st ate o f Cr∶YA G cr ystal.A cta O ptica Sinca,2001,21(2):225～227(in Chinese)2　Shimony Y,Burshtein Z,Ben-A mar Bar anga.Repetitive Q-sw itching of a CW N d∶Y A G laser using Cr∶Y A G sa t-ur able absor ber.IEEE J Q uant Elect ro n,1996,32(2):305～3103　Bai Y,W u N,Z ha ng J,L i J,Deng P.P assiv ely Q-sw itched Nd∶Y VO4laser w ith a Cr∶Y A G cr ystal sat ur able ab-sor ber.Appl O pt,1997,36(24):2468～24724　Shen H Y,Wu R F,Zeng Z D,et a l.L aser dio de pumping high-stabilit y1047nm T EM00mo de CW N d∶Y L F laser.Chinese Jour nal o f L aser s,2000,B9(2):103～1065　Bar tscgke J,Bo ller K J,K limov I V,et al.Diode-pum ped passiv ely Q-switched self-frequency-do ubling N d∶Y A G laser.J Opt So c Am,1997,B14(17):3452～34566　Zhao S,Zhang X,W ang Q.Dio de-la ser-pumped passively Q-sw itched Nd∶S-FA P gr een laser.SP IE,2000,3929:261～265二极管泵浦被动调Q N d∶YAG/KT P绿光激光器郑　权1　赵　岭2(1中国科学院长春光学精密机械与物理研究所,长春130022)(2中国科学院上海光学精密机械研究所,上海201800)收稿日期:2001-06-11摘　要　报道了LD泵浦的Nd∶YAG/KTP/Cr∶YAG结构被动调Q绿光激光器.当注入泵浦功率为750mW时,获得了平均功率38mW,脉冲宽度14.7ns,重复频率20.4kHz,峰值功率126.6W的调Q绿激光输出.关键词　LD泵浦;Nd∶YAG;被动调Q;绿激光Zheng Quan　w as born in Heilongjiang,China,o n July2,1973.He re-ceived the B.S.deg ree in1996and the M.S.degree in1999,fro mChang chun Institute of Optics and Fine Mechanics,China.He is presentlypursuing the Ph.D.degr ee in o ptics at Chang chun Institute of Optics,FineM echanics and Phy sics,CAS.He is interested in hig h performance so lid-state laser,high pow er gas laser,no nlinear optics,optical com municationand so on.62光子学报 31卷。