High Power Laser Bars for 70W CW(808nm)

PublicationDate :Oct．2011<Silicon RF Power MOS FET (Discrete)>RD70HVF1RoHS Compliance,Silicon MOSFET Power Transistor,175MHz70W 520MHz,50WDESCRIPTIONRD70HVF1is a MOS FET type transistor specifically designed for VHF/UHF High power amplifiers applications.FEATURESHigh power and High Gain:Pout>70W,Gp>10.6dB @Vdd=12.5V,f=175MHz Pout>50W,Gp>7.0dB @Vdd=12.5V,f=520MHz High Efficiency:60%typ.on VHF Band High Efficiency:55%typ.on UHF BandAPPLICATIONFor output stage of high power amplifiers in VHF/UHFBand mobile radio sets.RoHS COMPLIANTRD70HVF1-101is a RoHS compliant products.RoHS compliance is indicate by the letter “G”after the Lot Marking.ABSOLUTE MAXIMUM RATINGS(Tc=25°C UNLESS OTHERWISE NOTED)SYMBOL PARAMETERCONDITIONSRATINGSUNIT V DSS Drain to source voltage Vgs=0V 30V V GSS Gate to source voltage Vds=0V +/-20V Pch Channel dissipation Tc=25°C 150WPin Input power Zg=Zl=5010(Note2)W ID Drain current -20A Tch Channel temperature -175°C Tstg Storage temperature --40to +175°C Rth j-cThermal resistancejunction to case1.0°C/WNote 1:Above parameters are guaranteed independently.Note 2:Over 300MHz use spec is 20WELECTRICAL CHARACTERISTICS(Tc=25°C,UNLESS OTHERWISE NOTED)LIMITS UNIT SYMBOL PARAMETER CONDITIONSMIN TYP MAX.I DSS Zerogate voltage drain current V DS=17V,V GS=0V--300uAI GSS Gate to source leak current V GS=10V,V DS=0V--5uAV TH Gate threshold voltage V DS=12V,I DS=1mA 1.3 1.8 2.3V Pout Output power f=175MHz,V DD=12.5V7075-W ηD Drain efficiency Pin=6W,Idq=2.0A5560-% Pout Output power f=520MHz,V DD=12.5V5055-W ηD Drain efficiency Pin=10W,Idq=2.0A5055-%No destroy-Load VSWR tolerance V DD=15.2V,Po=70W(PinControl)f=175MHz,Idq=2.0A,Zg=50ΩLoadVSWR=20:1(All phase)No destroy-Load VSWR tolerance V DD=15.2V,Po=50W(PinControl)f=520MHz,Idq=2.0A,Zg=50ΩLoad VSWR=20:1(All phase)Note:Above parameters,ratings,limits and conditions are subject to change.TYPICALCHARACTERISTICSTYPICAL CHARACTERISTICSTYPICAL CHARACTERISTICSTEST CIRCUIT(f=175MHz)8pF37pF 138.543100pF2110micro strip line width=4.2mm/50OHM,er:2.7,t=1.6mm Note:Board material PTFE substrateC1:2200pF 10uF in parallel RF-OUTVggVddDimensions:mm56pF165C2:2200pF*2in parallel C3:2200pF,330uF in parallelL2:4Turns,I.D6mm,D1.6mm P=2silver plateted copper L1:5Turns,I.D6mm,D1.6mm P=1silver plateted copper wireTEST CIRCUIT(f=520MHz)100880-10pF5pF15pF0-10pF 5pF 15pF 807045L3:4Turns,I.D6mm,D1.6mm P=1silver plateted 1815pF 5pF401238micro strip line width=4.2mm/50OHM,er:2.7,t=1.6mm Note:Board material PTFE substrateC1:2200pF 10uF in parallel RF-OUTL1:4Turns,I.D6mm,D1.6mm P=1silver plateted copper wire VggVddDimensions:mm8100C2:2200pF*2in parallel C3:2200pF,330uF in parallelL2:2Turns,I.D6mm,D1.6mm P=2silver plateted copper wireINPUT/OUTPUT IMPEDANCE VS.FREQUENCY CHARACTERISTICSZo=10Ωf=135MHz Zoutf=175MHz Zoutf=175MHz Zinf=135MHz ZinZin,Zoutf Zin Zout(MHz)(ohm)(ohm)Conditions1350.43-j3.190.70+j0.25Po=90W,Vdd=12.5V,Pin=6W1750.55-j2.530.72-j0.36Po=80W,Vdd=12.5V,Pin=6Wf=520MHz ZoutZo=10Ωf=520MHz Zinf=440MHz Zoutf=440MHz ZinZin,Zoutf Zin Zout(MHz)(ohm)(ohm)Conditions4400.74-j0.340.71-j0.18Po=60W,Vdd=12.5V,Pin=10W520 1.04+j0.630.93+j1.62Po=55W,Vdd=12.5V,Pin=10WATTENTION:1.High Temperature;This product might have a heat generation while operation,Please take notice that havea possibility to receive a burn to touch the operating product directly or touch the product until cold after switchoff.At the near the product,do not place the combustible material that have possibilities to arise the fire.2.Generation of High Frequency Power;This product generate a high frequency power.Please take noticethat do not leakage the unnecessary electric wave and use this products without cause damage for human and property per normal operation.3.Before use;Before use the product,Please design the equipment in consideration of the risk for human andelectric wave obstacle for equipment.PRECAUTIONS FOR THE USE OF MITSUBISHI SILICON RF POWER DEVICES:1.The specifications of mention are not guarantee values in this data sheet.Please confirm additional detailsregarding operation of these products from the formal specification sheet.For copies of the formal specification sheets,please contact one of our sales offices.2.RA series products(RF power amplifier modules)and RD series products(RF power transistors)are designedfor consumer mobile communication terminals and were not specifically designed for use in other applications.In particular,while these products are highly reliable for their designed purpose,they are not manufactured under a quality assurance testing protocol that is sufficient to guarantee the level of reliability typically deemed necessary for critical communications elements and In the application,which is base station applications and fixed station applications that operate with long term continuous transmission and a higher on-off frequency during transmitting,please consider the derating,the redundancy system,appropriate setting of the maintain period and others as needed.For the reliability report which is described about predicted operating life time of Mitsubishi Silicon RF Products,please contact Mitsubishi Electric Corporation or an authorized Mitsubishi Semiconductor product distributor.3.RD series products use MOSFET semiconductor technology.They are sensitive to ESD voltage thereforeappropriate ESD precautions are required.4.In the case of use in below than recommended frequency,there is possibility to occur that the device isdeteriorated or destroyed due to the RF-swing exceed the breakdown voltage.5.In order to maximize reliability of the equipment,it is better to keep the devices temperature low.It isrecommended to utilize a sufficient sized heat-sink in conjunction with other cooling methods as needed(fan, etc.)to keep the channel temperature for RD series products lower than120deg/C(in case of Tchmax=150deg/C),140deg/C(in case of Tchmax=175deg/C)under standard conditions.6.Do not use the device at the exceeded the maximum rating condition.In case of plastic molded devices,theexceeded maximum rating condition may cause blowout,smoldering or catch fire of the molding resin due to extreme short current flow between the drain and the source of the device.These results causes in fire or injury.7.For specific precautions regarding assembly of these products into the equipment,please refer to thesupplementary items in the specification sheet.8.Warranty for the product is void if the products protective cap(lid)is removed or if the product is modified inany way from it’s original form.9.For additional“Safety first”in your circuit design and notes regarding the materials,please refer the last pageof this data sheet.10.Please refer to the additional precautions in the formal specification sheet.©2011MITSUBISHI ELECTRIC CORPORATION.ALL RIGHTS RESERVED.。

s Automatic leveling of output voltage as frequency is scanned or swept.
output terminals to provide up to 2 KV into 20,000 ohm load, 3 KHz to 30 KHz.
or sweeping mode for four frequency bands
this arrangement, the unit maintains a constant injection level (up to a maximum of 7.5 volts r.m.s.) as frequency is scanned or swept.
Maximum power output of the unit into a 1.5 ohm resistive load is over 300 watts and 200 watts into 2.5 ohms. The output voltage into a 0.5 ohm load connected to the secondary of the associated Type 6220-1A Transformer can be adjusted to a level in excess of ten volts at 1.0 KHz.
When used in conjunction with the Type 7021-1 Phase Shift Network and the Type 6220-1A Transformer, provision is made for sensing the audio voltage being injected into the EUT and displaying it on the digital panel meter. In

第50卷第4期2021年4月人㊀工㊀晶㊀体㊀学㊀报JOURNAL OF SYNTHETIC CRYSTALS Vol.50㊀No.4April,2021高可靠性无铝有源层808nm 半导体激光器泵浦源刘㊀鹏1,2,3,朱㊀振2,陈㊀康2,王荣堃1,夏㊀伟2,3,徐现刚1,2(1.山东大学,新一代半导体材料研究院,晶体材料国家重点实验室,济南㊀250100;2.山东华光光电子股份有限公司,济南㊀250101;3.济南大学物理科学与技术学院,济南㊀250022)摘要:针对高功率808nm 激光器泵浦源的应用需求,设计并制备了InGaAsP /GaInP 材料体系的无铝有源区半导体激光器㊂使用双非对称的限制层及波导层结构,降低了P 侧材料的热阻及光吸收㊂优化了金属有机化学气相沉积(MOCVD)中As 和P 混合材料的生长条件,制备出界面陡峭的四元InGaAsP 单晶外延薄膜㊂制作的激光器室温测试阈值电流为1.5A,斜率效率为1.26W /A,10A 下的功率达到10.5W,功率转换效率为58%㊂连续电流测试最大功率为23W@24.5A,准连续电流测试最大功率为54W@50A,没有产生灾变性光学损伤(COD)㊂在15A 电流加速老化下,激光器工作4200h 未出现功率衰减及COD 现象,说明制备的无铝有源区808nm 激光器具有高可靠性的输出性能㊂关键词:无铝材料;高可靠性;InGaAsP;808nm;非对称;泵浦源;半导体激光器中图分类号:TN248.4㊀㊀文献标志码:A ㊀㊀文章编号:1000-985X (2021)04-0757-05High Reliable Al-Free 808nm Semiconductor Laser Diode Pump SourceLIU Peng 1,2,3,ZHU Zhen 2,CHEN Kang 2,WANG Rongkun 1,XIA Wei 2,3,XU Xiangang 1,2(1.Institute of Novel Semiconductors,State Key Laboratory of Crystal Material,Shandong University,Jinan 250100,China;2.Shandong Huaguang Optoelectronics Co.,Ltd.,Jinan 250101,China;3.School of Physics and Technology,University of Jinan,Jinan 250022,China)Abstract :For 808nm high power laser used as pump source,Al-free active-region laser diode was designed and fabricated,consisting of InGaAsP /GaInP.In this work,a double asymmetric structure of cladding and waveguide layers to reduce the thermal resistance and optical loss of P-side layers were proposed.By optimizing the MOCVD growth of As and P hybrid material,InGaAsP single-crystal epitaxial film with steep interface was fabricated.The threshold current is 1.5A at room temperature and the slope efficiency is 1.26W /A.The output power is 10.5W at 10A and the power efficiency is 58%.Under continuous wave (CW)operation,the maximum output power is 23W@24.5A,while it can reach 54W@50A under quasi continuous wave (QCW)mode without catastrophic optical damage (COD).No power degradation or COD occurred for accelerated aging over 4200h at 15A,showing high long-term reliability of Al-free active-region 808nm laser diode.Key words :Al-free material;high reliabile;InGaAsP;808nm;asymmetric;pump source;semiconductor laser diode㊀㊀收稿日期:2021-03-01㊀㊀基金项目:山东省激光装备创新创业共同体项目㊀㊀作者简介:刘㊀鹏(1994 ),男,山东省人,硕士研究生㊂E-mail:seekersliupeng@㊀㊀通信作者:朱㊀振,博士,高工㊂E-mail:zhuzhen@ 徐现刚,博士,教授㊂E-mail:xxu@ 0㊀引㊀㊀言半导体激光器具有体积小㊁质量轻㊁效率高及易于集成等优点,在工业加工㊁智能传感㊁医养健康及固体和光纤激光器泵浦源等方面有着重要应用㊂其中808nm 半导体激光器是Nd 掺杂YAG 固体激光器的理想泵浦源,被广泛用于精细加工㊁雷达测距等领域[1-2]㊂除了激光器的功率和效率,可靠性是实际应用中最为关注的性能㊂随着激光器输出功率越来越高,灾变性光学损伤(COD)成为影响半导体激光器可靠性及寿命的关键因素㊂这和激光器的材料生长和腔面处理有直接关系㊂由于AlGaAs 材料生长工艺比较成熟,目前758㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第50卷808nm激光器大部分使用AlGaInAs/AlGaAs作为有源层㊂但是含铝材料不稳定,极易氧化形成缺陷并在材料内部延伸造成器件失效㊂国际上,大功率808nm激光器一般都在腔面做特殊处理来控制缺陷的产生或延伸,如美国II VI公司的E2工艺[3],德国FBH研究所的H离子清洗工艺[4]㊂但特殊处理会带来复杂的工艺问题,降低良率,给808nm激光器的批量化生产增加难度㊂本文通过量产型金属有机化学气相沉积(MOCVD)设备生长了InGaAsP/GaInP结构的808nm半导体激光器㊂由于有源区不含活泼性的铝元素,材料生长及腔面处理的工艺窗口较大,激光器的性能更加稳定和可靠㊂在15A电流加速老化下,激光器工作4200h未出现功率衰减及COD现象,10W工作寿命推测在40000h以上㊂本文是继承和发扬了蒋民华院士 为晶体提供泵源 的指导思想,不忘初心,通过各单位多年持久的产学研紧密结合,坚持创新,在山东华光光电子股份有限公司实现了规模化量产,满足了市场需求㊂同时开发了630~1100nm波段的多种半导体激光器泵浦源,其中808nm激光器由于具有优异的性能,是产业化较为成功的泵源之一㊂1㊀实㊀㊀验1.1㊀激光器结构如上所述,无铝结构的激光器在抑制体材料缺陷及提高腔面光学损伤方面有很多优势,但和传统的AlGaAs材料相比,InGaAsP/GaInP材料也有一些短板㊂根据JDSU的研究[5],GaInP材料的热导率是0.08W/(cm㊃K),为Al0.25Ga0.75As材料的一半,而其相同掺杂浓度下的电导率也要低于AlGaAs材料,这会影响激光器的高功率和高转换效率输出㊂在激光器外延结构设计上采用双非对称结构,如表1所示,P侧GaInP波导层的厚度要小于N侧GaInP波导层的厚度,P型AlGaInP限制层的Al组分要高于N型AlGaInP 限制层的Al组分㊂这不仅使光场偏向N区,降低空穴对光子的吸收,同时还能缩减P侧的外延层厚度,降低P区外延层的热阻及电阻㊂GaInP波导层中间为一层8nm厚度的InGaAsP单量子阱㊂InGaAsP材料可以通过调节III族及V族原子的组分实现量子阱的压缩和伸张应变,进而得到不同的激光偏振模式㊂为获得更低的阈值电流密度,可以使用压应变的InGaAsP量子阱㊂表1㊀808nm激光器的外延结构Table1㊀Epitaxial structure of808nm laser diodeLayer Material Thickness/nm Doping/cm-3Contact GaAs200>1ˑ1019P-cladding Al x Ga0.5-x In0.5P9001ˑ1018P-waveguide Ga0.5In0.5P400Quantum well InGaAsP8N-waveguide Ga0.5In0.5P800N-cladding Al y Ga0.5-y In0.5P15001ˑ1010Buffer GaAs2002ˑ1018为满足激光器耦合进入400μm芯径的光纤的需求,激光器发光区的宽度设计为390μm,周期为750μm,腔长为2mm㊂1.2㊀激光器制备外延材料生长使用量产型MOCVD系统㊂衬底为偏向<111>A方向15ʎ的GaAs(100)晶面,可以有效抑制GaInP材料的有序结构,增加材料生长窗口㊂III族有机源采用三甲基镓(TMGa)㊁三甲基铝(TMAl)和三甲基铟(TMIn),V族源材料为砷烷(AsH3)和磷烷(PH3),N型掺杂为Si,P型掺杂为Mg㊂外延层生长过程的温度控制在600~700ħ,反应室压力为104Pa㊂量子阱是整个激光器结构的核心,其生长质量决定了激光器的性能㊂InGaAsP为四元材料,且AsH3和PH3在不同生长条件下的分配系数差别较大,需要对量子阱的生长方式进行特殊设计㊂如图1所示,通过优化量子阱及两侧界面的生长温度及气流切换方式,得到界面陡峭的InGaAsP量子阱㊂外延层的结晶质量和表面状态也会影响激光器的性能参数㊂图2是经过优化后㊀第4期刘㊀鹏等:高可靠性无铝有源层808nm半导体激光器泵浦源759㊀的单层GaInP的原子力显微镜(AFM)照片,可以看到外延层的表面非常平整,粗糙度Ra仅为0.13nm,很接近外延生长前的GaAs衬底表面㊂图1㊀GaInP/InGaAsP量子阱的TEM照片Fig.1㊀TEM image of GaInP/InGaAsP quantum well图2㊀GaInP外延层的AFM照片Fig.2㊀AFM image of GaInP epitaxial layer 外延片生长完成以后进行芯片工艺的制作㊂使用湿法腐蚀工艺形成390μm的宽条,并在宽条两侧覆盖SiO2绝缘膜,形成电流注入区㊂P面金属电极为Ti/Pt/Au,N面金属电极为Ge/Ni/Au㊂解理成2mm腔长的巴条,使用电子束蒸发设备在前后腔面分别蒸镀5%的增透膜及98%的高反膜㊂解离成管芯,P面朝下烧结于AlN陶瓷材料的AuSn热沉上㊂2㊀结果与讨论为验证设计的外延结构及生长的材料质量,测试并计算了芯片的内量子效率和腔内损耗㊂将工艺晶片分别解理成1.0mm㊁1.5mm㊁2.0mm㊁2.5mm四种腔长的巴条,在未镀膜的条件下,利用脉冲电流分别测试它们的斜率效率和阈值电流,然后通过数值拟合,得到图3和4的曲线㊂通过计算得到芯片的内量子效率ηi 为97%,光吸收损耗系数αi为1.1cm-1,透明电流密度J tr为96A㊃cm-2,模式增益系数ΓG0为15cm-1㊂这个结果同德国Jenoptik公司及FBH研究所报道的808nm激光器结果是接近的[6-7]㊂图3㊀外微分量子效率和腔长的拟合曲线Fig.3㊀Curve of external differential efficiency and cavity length图4㊀阈值电流密度和腔长的拟合曲线Fig.4㊀Curve of threshold current density and cavity length图5为封装后的808nm激光器在25ħ条件下的功率-电流-电压曲线㊂从图中可以看出,激光器的阈值电流为1.5A,对应的阈值电流密度为192A㊃cm-2㊂激光器的斜率效率为1.26W/A,对应的外量子效率为82%㊂在10A电流下,激光器的输出功率达到了10.5W,电压1.82V,转换效率为58%㊂图6为热沉温度分别是25ħ㊁35ħ㊁45ħ及55ħ下的功率及电压曲线㊂随着温度增加,激光器的载流子溢出变得严重,阈值电流会增加,斜率效率会下降㊂由于P型限制层使用了高带隙的AlGaInP材料,高温下可以很好地将载流子限制在有源区内,激光器在55ħ及10A电流下的输出功率仍达到了9.3W,具有较好的温度特性㊂图7是激光器在10A电流下测试的光谱曲线㊂其峰值波长为807.9nm,光谱的半高宽(FWHM)为1.7nm㊂图8是激光器的远场特性测试㊂激光器工作时的水平发散角为9ʎ,垂直发散角为31ʎ㊂760㊀研究论文人工晶体学报㊀㊀㊀㊀㊀㊀第50卷图5㊀808nm LD的功率-电流-电压曲线Fig.5㊀Power-current-voltage curves of808nm LD图6㊀不同温度下的808nm LD功率曲线Fig.6㊀Power curves of808nm LD at different temperatures图7㊀808nm LD的光谱曲线Fig.7㊀Optical spectrum of808nm LD图8㊀808nm LD的远场发散角Fig.8㊀Far field angle of808nm LD图9㊀CW及QCW大电流测试下的功率曲线Fig.9㊀Power curves at high current CW and QCW testing图10㊀激光器加速老化曲线Fig.10㊀Accelerated aging curves of the laser 808nm的大功率激光器一般在工业及特种行业中作为泵浦源使用,需要具有高的可靠性㊂由于大功率激光器的主要失效模式为COD造成的突然失效,其COD功率是影响激光器可靠性的重要因素㊂在实验中,可以通过大电流测试考评激光器的COD水平㊂图9为连续电流(CW)及准连续电流(QCW,脉宽1ms,周期100ms)模式测试下的激光器功率曲线图㊂受限于测试电源的最大电流,激光器在CW24.5A下功率达到了23W,在QCW50A下的功率达到了54W,并且两种测试方式均没有COD产生,说明制作的808nm激光器的腔面COD功率在54W以上,具有高的抗腔面光学损伤特性㊂激光器的寿命和稳定性可以通过提高电流或温度的加速老化方式进行快速考评㊂由于808nm激光器的主要失效原因是腔面COD,提高电流(功率)的加速方式更能反映808nm激光器的可靠性水平㊂国内外同行大部分使用12A以内的加速电流进行老化[6,8-9],鉴于无铝结构激光器在抗腔面光学损伤方面的优势,使用更高的15A加速电流㊂图10是10只㊀第4期刘㊀鹏等:高可靠性无铝有源层808nm半导体激光器泵浦源761㊀808nm激光器在15A电流㊁水冷温度25ħ下的在线监控老化曲线㊂经过4200h的老化,激光器没有出现功率衰减及突然失效现象㊂通过文献所用的加速因子计算方法[10],推算808nm激光器在10W下的寿命为40000h以上,12W下的寿命也在20000h以上㊂3㊀结㊀㊀论本文使用MOCVD方法生长了高质量的InGaAsP/GaInP材料体系的激光器外延片,并制作了390μm条宽及2mm腔长的器件㊂室温测试阈值电流为1.5A,斜率效率1.26W/A,10A下的功率达到10.5W,转换效率为58%㊂CW电流测试最大功率为23W@24.5A,QCW电流测试最大功率为54W@50A㊂在15A电流加速老化下,激光器工作4200h未出现功率衰减及COD现象,推算808nm激光器在10W下的寿命为40000h以上,12W下的寿命在20000h以上㊂参考文献[1]㊀陈良惠,杨国文,刘育衔.半导体激光器研究进展[J].中国激光,2020,47(5):13-31.CHEN L H,YANG G W,LIU Y X.Development of semiconductor lasers[J].Chinese Journal of Lasers,2020,47(5):13-31(in Chinese).[2]㊀宁永强,陈泳屹,张㊀俊,等.大功率半导体激光器发展及相关技术概述[J].光学学报,2021,41(1):0114001.NING Y Q,CHEN Y Y,ZHANG J,et al.Brief review of development and techniques for high power semiconductor lasers[J].Acta Optica Sinica,2021,41(1):0114001(in Chinese).[3]㊀EPPERLEIN P W.Semiconductor laser engineering,reliability and diagnostics[M].John Wiley&Sons Ltd:Wiley,2013.[4]㊀CRUMP P,WENZEL H,ERBERT G,et al.Passively cooled TM polarized808nm laser bars with70%power conversion at80W and55Wpeak power per100μm stripe width[J].IEEE Photonics Technology Letters,2008,20(16):1378-1380.[5]㊀PETERS M,ROSSIN V,ACKLIN B.High-efficiency high-reliability laser diodes at JDS Uniphase[C]//Lasers and Applications in Science andEngineering.Proc SPIE5711,High-Power Diode Laser Technology and Applications III,San Jose,California,USA.2005,5711:142-151.[6]㊀PIETRZAK A,HüLSEWEDE R,ZORN M,et al.High-power single emitters and low fill factor bars emitting at808nm[C]//SPIE LASE.ProcSPIE9733,High-Power Diode Laser Technology and Applications XIV,San Francisco,California,USA.2016,9733:97330R. [7]㊀KNAUER A,ERBERT G,STASKE R,et al.High-power808nm lasers with a super-large optical cavity[J].Semiconductor Science andTechnology,2005,20(6):621-624.[8]㊀REN Z Q,LI Q M,LI B,et al.High wall-plug efficiency808-nm laser diodes with a power up to30.1W[J].Journal of Semiconductors,2020,41(3):61-63.[9]㊀MARTIN HU H,QIU B C,WANG W M,et al.High performance808nm GaAsP/InGaP quantum well lasers[C]//SPIE/COS Photonics Asia.Proc SPIE10017,Semiconductor Lasers and Applications VII,Beijing,China.2016,1001:100170M.[10]㊀BAO L,KANSKAR M,DEVITO M,et al.High reliability demonstrated on high-power and high-brightness diode lasers[C]//SPIE LASE.ProcSPIE9348,High-Power Diode Laser Technology and Applications XIII,San Francisco,California,USA.2015,9348:93480C.。

Compact dual-wavelength Nd:GdVO4 laserworking at 1063 and 1065 nmBo Wu, Peipei Jiang, Dingzhong Yang, Tao Chen, Jian Kong, and Yonghang Shen* State Key Laboratory of Modern Optical Instrumentation, Zhejiang University,Hangzhou 310027, China*Correspondance: e-mail: physyh@, tel: +86 571 87952392Abstract: We report a compact diode-laser pumped Nd:GdVO4 laser withstable dual-wavelength output at 1063 nm and 1065 nm simultaneously.Two types of resonant cavity configurations were presented to support thestable dual-wavelength operation of the laser. Using a polarization beamsplitter(PBS) included T-shaped cavity, we obtained a total power outputover 5W in two orthogonal polarized beam directions with 4 W in σpolarization (1065.5 nm) and 1W in πpolarization (1063.1 nm). Bycombining a half-wave-plate with the PBS in the laser cavity, a newconfiguration favoring one beam direction dual-wavelength output withsame polarization direction was realized. A phenomenon of further linesplitting was observed in both 1065 nm and 1063 nm.©2009 Optical Society of AmericaOCIS codes: 140.3410; 140.3580References and Links1. C. G. Bethea, “Megawatt power at 1.318µ in Nd3+:YAG and simultaneous oscillation at both 1.06 and1.318µ,” IEEE. J. Quantum Electron 9, 254-254 (1973).2.H. Y. Shen, R. R. Zeng, Y. P. Zhou, G. F. Yu, C. H. Huang, Z. D. Zeng, W. J. Zhang and Q. J. Ye,“Simultaneous multiple wavelength laser action in various neodymium host crystals,” IEEE. J. QuantumElectron 27, 2315-2318 (1991).3.M. B. Danailov and I. Y. Milev, “Simultaneous multiwavelength operation of Nd:YAG laser,” Appl. Phys.Lett. 61, 746-748 (1992).4.W. Vollmer, M. G. Knight, G. A. Rines, J. C. MeCarthy, E. P. Chicklis, “Five-color Nd:YLF laser,”in:Digest of Conference on Lasers and Electro-Optics, Paper THM 2, Optical Society of America, Washington, DC, 188 (1983).5.H. Y. Zhu, G. Zhang, C. H. Huang, Y. Wei, L. X. Huang, A. H. Li, Z. Q. Chen, “1318.8nm/1338.2nmsimultaneous dual-wavelength Q-switched Nd:YAG laser,” Appl. Phys. B 90, 451-454 (2008).6.Y. F. Chen, “cw dual-wavelength operation of a diode-end-pumped Nd:YVO4 laser,” Appl. Phys. B 70, 475-478 (2000).7.R. Zhou, B. G. Zhang, X. Ding, Z. Q. Cai, W. Q. Wen, P. Wang and J. Q. Yao, “Continuous-wave operationat 1386nm in a diode-end-pumped Nd:YVO4 laser,” Opt. Express 13, 5818-5824 (2005).8.8. Y. Y. Lin, S. Y. Chen, A. C. Chiang, R. Y. Tu, and Y. C. Huang, “Single-longitudinal-mode, tunable dual-wavelength, CW Nd:YVO4 laser,” Opt. Express 14, 5329-5334 (2006).9.R. Zhou, E. B. Li, B. G. Zhang, X. Ding, Z. Q. Cai, W. Q. Wen, P. Wang, and J. Q. Yao, “Simultaneousdual-wavelength CW operation using 4F3/2-4I13/2 transitions in Nd:YVO4 crystal,” Opt. Commun. 260, 641-644 (2006).10.H. Y. Shen, R. R. Zeng, Y. P. Zhou, G. F. Yu, C. H. Huang, Z. D. Zeng, W. J. Zhang and Q. J. Ye,“Comparison of simultaneous multiple wavelength lasing in various neodymium host crystals at transitions from 4F3/2-4I11/2 and 4F/3/2-4I13/2,” Appl. Phys. Lett. 56, 1937-1938 (1990).11. C. H. Huang, G. Zhang, Y. Wei, L. X. Huang, H. Y. Zhu, “A Q-switched Nd:YAlO3 laser emitting 1080 and1342nm,” Opt. Commun. 281, 3820-3823 (2008).12.H. H. Yu, H. J. Zhang, Z. P. Wang, J. Y. Wang, Y. G. Yu, Z. B. Shi, X. Y. Zhang, and M. H. Jiang, “High-power dual-wavelength laser with disordered Nd:CNGG crystals,” Opt. Lett. 34, 151-153 (2009).13.J. L. He, J. Du, J. Sun, S. Liu, Y. X. Fan, H. T. Wang, L. H. Zhang, and Y. Hang, “High efficiency single-and dual- wavelength Nd:GdVO4 lasers pumped by a fiber-couple diode,” Appl. Phys. B 79, 301-304 (2004).#107766 - $15.00 USD Received 20 Feb 2009; revised 15 Mar 2009; accepted 17 Mar 2009; published 30 Mar 2009 (C) 2009 OSA13 April 2009 / Vol. 17, No. 8 / OPTICS EXPRESS 600414.K. Lunstedt, N. Pavel, K. Petermann, and G. Huber, “Continuous-wave simultaneous dual-wavelengthoperation at 912nm and 1063nm in Nd:GdVO4,” Appl. Phys. B 86, 65-70 (2007).15. A. I. Zagumennyi, V. G. Ostoumov, I. A. Shcherbakov, T. Jensen, J.-P. Meyn, and G. Huber, “TheNd:GdVO4 crystal: a new material for diode-pumped laser,” Sov. J. Quantum Electron 22, 1071-1072(1992).16.Y. Sato, N. Pavel, and T. Taira, “Spectroscopic properties and near quantum-limit laser-oscillation inNd:GdVO4 single crystal,” in OSA TOPS on Advanced Solid-State Photonics, Vol. 94, G. J. Quarles, ed.,(Optical Society of America, Washington, DC), 405-409 (2004).IntroductionLasers emitting simultaneously at multiple wavelengths can find wide applications in manyfields such as environmental monitoring, laser radar, spectral analysis and THz research, etc.In traditional laser systems, however, only one wavelength (or line) operation can normally beobtained if no special measure is taken. The emission lines with weak gain are usuallydepressed by the line with strong gain because of the gain competition between the laseremission lines, and this competition generally results in only the laser line with the strongestgain being generated. To meet the requirement of simultaneously multiple laser lineoscillation, special design of the laser oscillation cavity is necessary to control and to reducethe gain competition among the multiple wavelength lines of the gain medium. To ourknowledge, the first report about the multiple wavelength laser was presented by Bethea in1973 by using a Nd:YAG as the gain medium [1]. After that, multiple wavelength lasers basedon Nd:YAG[2-4], Nd:YLF[5], Nd:YVO4[6-9], Nd:YAP[10,11] and Nd:CNGG[12] have beenreported, by means of designing a typical coating for the output coupler, generating inspatially shifted regions of the gain medium and using two quarter wave plates (QWP) tomake the intrinsic frequency split, etc. With Nd:GdVO4crystal, multi-wavelength laseroperation was also realized at 1063 nm and 1342 nm[13], or at 912nm and 1063nm[14].However, to our knowledge, no work on the simultaneous multi-wavelength laser operation attwo close wavelengths of 1063 nm and 1065 nm with Nd:GdVO4 crystal was once reported.Such a dual-wavelength laser would be especially valuable as a compact and strong lasersource to generate the THz emission because the frequency difference between 1063 nm and1065 nm is about 0.53 THz.Since being first introduced by Zaguniennyi et al in 1992[15], the Nd:GdVO4 crystal hasbeen proved very suitable for high power laser system. It has the characteristics of strongpolarization dependent absorption spectra and fluorescent emission spectra. The strongestemission line of Nd:GdVO4 is typically 1063.1 nm in π polarization (E//c). Comparing withthis line, the emission lines of 1063.1 nm and 1065.5 nm in σ polarization (E⊥c) are mediumstrong[16]. However, because the gain of 1063.1 nm in π polarization(emission cross section σ=10.3×10-19 -cm2) is almost five times higher than that of both 1063.1 nm and 1065.5 nm in σ polarization(σ=2.1×10-19 -cm2) [16], the σ polarization emission is normally depressed bythe π polarization emission of 1063.1 nm if no specific measure is applied to control the gaincompetition in the laser cavity. In this paper, we will present our recent results of exploring adual-wavelength Nd:GdVO4laser. By separating the orthogonal polarized beams with apolarization beam splitter(PBS) and then controlling their feedback separately, simultaneousdual-wavelength Nd:GdVO4 laser operation was stably realized at two close wavelengths of1063 nm and 1065 nm. To our knowledge, this is the first work of realizing dual-wavelengthlaser operation by means of polarization dependent gain control. The method presented in thispaper can be extended to other polarization dependent solid state laser, such as those with hostmaterials of YVO4, YAP, YLF or even ruby for dual-wavelength output.#107766 - $15.00 USD Received 20 Feb 2009; revised 15 Mar 2009; accepted 17 Mar 2009; published 30 Mar 2009 (C) 2009 OSA13 April 2009 / Vol. 17, No. 8 / OPTICS EXPRESS 6005Experiment and result analysisThe phenomenon of simultaneous dual-wavelength laser oscillation at both 1063 nm and 1065 nm was once observed from an end pumped normal Nd:GdVO 4 laser. We noted the laser wavelength switched from 1065 nm (σ polarization) to 1063 nm(π polarization) when the pump power increased gradually. Further analysis showed the phenomenon was resulted from the feedback difference between the π polarization and σ polarization, which was caused by the output coupler. It was then noted there existed a narrow transition pump power range, in which dual-wavelength output with orthogonal polarization direction could be realized. However, as the gain competition between the modes of π polarization and σ polarization still existed in the system, the dual-wavelength output was severely unstable and the mode shifting occurred from time to time between π polarization and σ polarization.fiberσFig. 1. T-shaped cavity configurationfeaturing orthogonal polarized two beam output. M1:input mirror, M2 and M3: output couplers for σ polarized 1065 nm emission and π polarized1063 nm emission respectively.In order to obtain a practically applicable dual-wavelength laser with stable power output, we designed a T-shaped cavity as shown in Fig. 1. The Nd:GdVO 4 laser was end pumped by a fiber-pigtailed laser diode working at 808 nm(LIMO60-F400-DL808M3, LIMO Corp., German) with a maximum power output of 60 W. A piece of Nd:GdVO 4 crystal (Nd 3+ doping, 0.5at%, from WITCORE company, China) with size of 3×3×8 (mm) was used as the gain medium. Both sides of the crystal were anti-reflection coated at 1064 nm and 808 nm. The crystal was wrapped using an indium foil and placed onto an aluminum stage for temperature stabilization. The input mirror of the cavity was flat with coating of high reflection around 1064 nm and transmittance of 95% at 808 nm. A PBS was placed in the cavity to split the beams polarizing in two orthogonal directions. The output coupler for the mode with horizontal polarization, M2, was a concave mirror with a radius of curvature -1000 mm and was coated with transmittance of 10% around 1064nm. Another concave mirror, M3, with a radius of curvature -500 mm was used as the output coupler for the mode with vertical polarization and was coated with transmittance of 30% around 1064 nm.#107766 - $15.00 USD Received 20 Feb 2009; revised 15 Mar 2009; accepted 17 Mar 2009; published 30 Mar 2009(C) 2009 OSA 13 April 2009 / Vol. 17, No. 8 / OPTICS EXPRESS 6006Fig. 2. Power dependence of the π polarized and the σ polarized laser emissions on the pumppower in the T-shaped cavity.By using such a T-shaped cavity configuration, stable dual-wavelength laser emission of 1063 nm (π polarization) and 1065 nm (σ polarization) was simultaneously obtained in two directions with much better power stability over a large adjustable power range as shown in Fig. 2. The laser power output of both the π polarized 1063.1 nm and the σ polarized 1065.5 nm beams increased simultaneously with the pump power until the pump power reached 33W.A total output power over 5W was obtained with 4 W in the σ polarization (1065.5 nm) and 1W in the π polarization (1063.1 nm). It was found in the experiment that the oscillation at 1065.5nm (σ polarized) was much more sensitive to the environmental factors than that at 1063.1nm (π polarized). Slight temperature fluctuation and pump power variation might induce strong mode competition and then large power fluctuation. Such power fluctuations were especially distinct as shown in Fig. 2 when the pump power was 23W and 29W respectively. With pump power higher than 34W, the output power of the σ polarized beam decreased quickly as a result of the net gain increase of π polarized oscillation at 1063.1nm. In the mean time, the power of π polarized beam rapidly increased and finally overrun its counterpart at 1065.5 nm. It was noted the saltation point of the pump power (pump power 39.4W) was strongly affected by the transmittances of the two output couplers, M2 and M3, and could thus be adjusted accordingly for system optimization. The spectrum of the laser emissions, as shown in Fig. 3 was measured by using an optical spectral analyzer (OSA, Ando AQ6317C) with a spectral resolution of 0.01nm when two output beams from the perpendicular directions were directed together onto an optical fiber using mirror reflectors. 1.41.21.00.80.60.40.20.0P o w e r(W ) x 10-610671066106510641063Wavelength(nm)Fig 3. Spectrum of the output emissions measured when two output beams from theperpendicular directions of the T-shaped cavity were directed together.#107766 - $15.00 USD Received 20 Feb 2009; revised 15 Mar 2009; accepted 17 Mar 2009; published 30 Mar 2009(C) 2009 OSA 13 April 2009 / Vol. 17, No. 8 / OPTICS EXPRESS 6007Fig. 4. Cavity configuration featuring one beam π polarized multi-wavelength laser output. ThePBS also acted as the output coupler of the vertical polarized laser beam. D-Detector.Because the laser output from the cavity configuration as shown in Fig. 1 featured two beams, it is sometimes inconvenient for applicants though the beams can be easily recombined using reflectors and PBS. To improve this, another cavity configuration featuring one beam output was presented as shown in Fig. 4. A half-wave plate (HWP) was included between the PBS, which also acted as an output coupler here, and the Nd:GdVO 4 crystal. It is not difficult to understand the polarization direction of the beams oscillating in the cavity would rotate (for both polarizations) according to the axis direction of the HWP when the beams pass the HWP. After the HWP, the portion of the beams with horizontal polarization would transmit through the PBS and reflect back by mirror M2 and then transmit through the PBS again without further loss, while the other portion of the beams with vertical polarization would be reflect out of the cavity by the PBS as the laser output. The beams feeding back from M2 and passing through the PBS were all polarizing in horizontal direction but would experience further polarization rotation when they reversely pass the HWP. The π polarized and σ polarized beams after the HWP would then be amplified separately depending on their gains in these polarization directions. The remained horizontal polarized beam at 1063.1 nm and vertical polarized beam at 1065.5 nm would not experience amplification in this round trip but would merge to the whole beam after they pass the HWP again. Thus, there would be no extra loss incurred if the transmittance of the HWP was perfect. In this way, the gains for beams with π polarization and σ polarization could be modified continuously by rotating the HWP. As a result, the laser could easily be regulated to work in single wavelength mode or in multi–wavelength mode. Under this configuration, dual wavelength laser emission with power output exceeding 1W was obtained when the pump power was 15 W. As the transmittance of the HWP we used was not good enough in this experiment, no higher pump power was applied for the time being. By measuring the spectra of the laser emission with the OSA(with the same spectral resolution of 0.01nm), we found there existed a HWP position with dual-wavelength output at 1063.7 nm and 1065.5 nm as shown in Fig. 5 (It was noted the wavelength values were not exactly the same as that obtained in the T-shaped cavity configuration). Besides, the phenomenon of further laser line splitting was also observed. Both the laser lines at 1065 nm and at 1063 nm might split into two lines when the HWP was rotated. When the HWP was rotated to a specific direction, for example, there were two lines near 1063 nm which were corresponded to the former line of 1063.1 nm. Similar to this, there were also severalHWP directions with two laser lines near 1065 nm which were #107766 - $15.00 USD Received 20 Feb 2009; revised 15 Mar 2009; accepted 17 Mar 2009; published 30 Mar 2009(C) 2009 OSA 13 April 2009 / Vol. 17, No. 8 / OPTICS EXPRESS 6008corresponded to the former line of 1065.7 nm. In a whole, as many as 10 lines (5 couples of lines) have been observed during the experiment and the spectra of some of these emission lines are illustrated in Fig. 5. 302520151050P o w e r (W ) x 10-610671066106510641063Wavelength (nm)(a)302520151050P o w e r (W ) x 10-610671066106510641063Wavelength(nm)(b)403020100P o w e r (W ) x 10-610671066106510641063Wavelength (nm)(c)Fig 5. The laser output spectra when the HWP was rotated, showing (a) the emission lines at1063.8 nm and 1065.5 nm. (b) the emission line at 1065 nm splitting into two lines at 1065.3nm and 1065.6 nm, or into other two lines at 1065.5 nm and 1065.8 nm; (c)the emission line at1063 nm splitting into two lines at 1062.7 nm and 1063.0 nm, 1063.2 nm and 1063.5 nm,1063.6 nm and 1063.8 nm respectively;It is interesting to note that in most cases the emission lines appeared in pair. Though the wavelength values of these lines were found to vary with the HWP direction, the wavelength difference within the pair lines seems unchanged (a value between 0.2 and 0.3 nm, limited by the resolution of the OSA). We believe this phenomenon might relate to the additional phase difference of two orthogonal polarized beams through the HWP, one experiencing amplification in the Nd:GdVO 4 crystal while another not. Deeper understanding of this emission line splitting may require further effort.ConclusionBriefly in summary, we succeeded in obtaining a stable dual-wavelength output at 1063 nm and 1065 nm simultaneously by designing two types of cavity configuration in a Nd:GdVO 4 laser. A T-shaped cavity favored stable π and σ polarization emission output in two perpendicular directions. A total power output of over 5 W was realized. A HWP included cavity favored continuously adjustable one beam dual-wavelength and multi-wavelength emission output. The phenomenon of further laser line splitting at both wavelengths of 1063 nm and 1065 nm was observed in the HWP included cavity configuration. Higher power output of dual-wavelength operation can be expected in both cavities by optimizing the parameters of cavity reflectivity and the transmittance of the HWP.This work was partly supported by Natural Science Foundation of China (project No. 60778001), the program for NCET in University and the National Basic Research Program (973) of China (2007CB307003).#107766 - $15.00 USD Received 20 Feb 2009; revised 15 Mar 2009; accepted 17 Mar 2009; published 30 Mar 2009(C) 2009 OSA 13 April 2009 / Vol. 17, No. 8 / OPTICS EXPRESS 6009。