摘要
针对1.5μm激光的广泛应用需求,设计并实现了一种基于KTiOAsO_(4)(KTA)晶体的外腔型光参量振荡器,其重复频率为10 kHz。研究采用主振荡功率放大器构建1 064 nm泵浦源系统:分别以808 nm和878 nm激光二极管作为主振荡器与功率放大器的泵浦,以Nd:YVO_(4)晶体作为增益介质,结合电光调Q技术,获得重复频率为10 kHz、平均功率为20.13 W的1 064 nm激光输出,x、y方向上的光束质量因子M^(2)均优于1.5。基于该泵浦源,构建双程泵浦平平腔KTA-OPO,系统性地研究了泵浦光斑直径和谐振腔长度对KTA-OPO泵浦阈值及输出功率的影响。经过优化后,在腔长为40 mm、泵浦光斑直径为430μm的条件下,系统可获得6.26 W的1 535.5 nm激光输出,光光转换效率达33%。文中研究采用外腔型KTA-OPO结构,提高了高重频1.5μm激光的输出功率。
Objective The 1.5μm laser is located both in the near-infrared atmospheric window and in the eye-safe wavelength band,so there is a wide demand for 1.5μm lasers in fields such as optical communication,laser ranging,and lidar.Currently,optical parametric oscillators(OPOs)based on the principle of nonlinear frequency conversion,represent a prominent approach for generating 1.5μm lasers.KTiOAsO4(KTA)is an ideal material for generating 1.5μm laser output via OPO technology due to its high nonlinear coefficient,broad transmission range,and high damage threshold.However,research in this field has primarily focused on extracavity OPOs operating below 100 Hz and intracavity OPOs operating above kHz.While low repetition frequency extracavity KTA-OPOs have successfully achieved high power 1.5μm laser output,the output power levels of high repetition frequency intracavity KTA-OPOs are generally lower due to limitations of intracavity power density.In response to the current research status and the demand for high repetition frequency and high power 1.5μm lasers in application fields,the 10 kHz 1.5μm laser output power is enhanced by utilizing extracavity KTA-OPO.Methods To obtain a pump beam with a repetition rate of 10 kHz and good beam quality,a master oscillator power amplifier(MOPA)system was constructed using LD end-pumped Nd:YVO_(4) crystals.The 1064 nm oscillator utilizes a BBO crystal for electro-optic Q-switching to achieve a 10 kHz laser,and three-stage amplification is carried out afterwards.In the amplifier stages,to minimize the impact of thermal effects,the first two stages employ single-end pumping,while the third stage uses dual-end pumping.Lenses are placed between each stage to ensure good mode matching between the pump and oscillation spots.During the OPO stage,a planeplane cavity OPO is built using KTA as the nonlinear crystal to achieve type II non-critical phase matching for the generation of 1.5μm parametric light.The optical-to-optical conversion efficiency is enhanced by optimizing the pump spot size and the oscillator cavity length(Fig.1).Results and Discussions Through electro-optic Q-switching technology,the oscillator achieves a 1064 nm laser output of 1.02 W,with a repetition rate of 10 kHz and a pulse width of 7.1 ns.The beam quality factors are M^(2) x=1.18 and M^(2) y=1.20(Fig.2).Using 878 nm LDs as the pump sources,the oscillator power was successfully increased to 6.26 W,12.40 W,and 20.13 W.The corresponding beam qualities are as follows:for the first stage,M^(2) x=1.20,M^(2) y=1.26;for the second stage,M^(2) x=1.32,M^(2) y=1.26;for the third stage,M^(2) x=1.42,M^(2) y=1.49(Fig.4).With a cavity length of 40 mm and a pump spot diameter of 430μm,the KTA-OPO generates a laser with a central wavelength of 1535.8 nm and a maximum output power of 6.26 W(Fig.5).The corresponding optical-tooptical conversion efficiency is 33%,with a pulse width of 7.2 ns and a linewidth of 0.26 nm.The beam quality factors are M^(2) x=2.75 and M^(2) y=3.81(Fig.6).Conclusions A high-power 1.5μm laser with a repetition frequency of 10 kHz has been successfully obtained using an extracavity KTA-OPO structure.To achieve high beam quality pump beam,a MOPA was constructed using LD end-pumped Nd:YVO_(4) crystals.By combining single-end pumping and double-end pumping in a three-stage amplification,a 1064 nm pump light with a beam quality factor better than 1.5 and a pulse repetition rate of 10 kHz was obtained,with an average power of 20.13 W.In the aspect of the KTA-OPO,the effects of cavity length and pump spot diameter on the pump threshold and conversion efficiency were comparatively studied.The pump spot parameters and resonator parameters were optimized to improve the conversion efficiency of the KTAOPO,1.5μm pulsed laser with an average power of 6.26 W and a pulse width of less than 10 ns,corresponding to an optical-to-optical conversion efficiency of up to 33%.Adoption of extracavity KTA-OPO structure effectively improves the high-frequency 1.5μm laser output power.Subsequent improvements should focus on enhancing the 1064 nm pump laser power while maintaining good beam quality.Additionally,adopting a ring cavity structure could further optimize the beam quality of the KTA-OPO.Moreover,single-frequency seed injection could be employed to narrow the output linewidth,thereby meeting practical application requirements.
作者
刘景
孟君
刘高佑
刘兆军
LIU Jing;MENG Jun;LIU Gaoyou;LIU Zhaojun(School of Information Science and Engineering,and Key Laboratory of Laser&Infrared System(Shandong University),Ministry of Education,Shandong University,Qingdao 266237,China;Shandong Provincial Key Laboratory of Laser Technology and Application,Shandong University,Qingdao 266237,China)
出处
《红外与激光工程》
北大核心
2025年第7期146-154,共9页
Infrared and Laser Engineering
