声光调Q Nd:YVO_(4)晶体级联拉曼倍频窄脉宽657 nm激光器

Frequency doubling of acousto-optic Q-switched Nd:YVO_(4)cascaded Raman laser for narrow pulse-width 657 nm laser

本工作对声光调Q的Nd:YVO_(4)晶体级联自拉曼腔内二阶斯托克斯光倍频实现窄脉宽红光激光进行了研究.从改善自拉曼晶体热效应出发,综合考虑基频激光性能和提高拉曼变频性能,设计了三段式键合YVO_(4)/Nd:YVO_(4)/YVO_(4)晶体来提升拉曼转换效率和输出功率.选用针对二阶斯托克斯波长倍频的室温临界相位匹配切割的LBO晶体作为非线性光学晶体.其匹配角度(θ=86.0°,φ=0°)非常接近非临界相位匹配,具有较小的走离角,有利于实现高效的倍频转换效率.通过抽运光束腰位置、声光调Q重复频率等参数优化,在14.2 W抽运功率和60 kHz重复频率下,获得最高平均输出功率1.63 W、转换效率11.5%的657 nm红光激光输出.657 nm红光的脉冲宽度为11.5 ns,窄于普通掺钕激光晶体1.3μm波段激光倍频实现的红光激光,表明通过级联拉曼倍频技术可发挥拉曼过程脉宽压缩特性实现较窄脉宽红光激光输出.

Frequency doubling of second-Stokes in an acousto-optic Q-switched Nd:YVO_(4)cascaded self-Raman cavity is demonstrated to achieve a narrow pulse-width red laser.A three-stage bonded YVO_(4)/Nd:YVO_(4)/YVO_(4)crystal is designed by comprehensively considering the improvement of thermal effect,the performance of fundamental frequency laser and Raman conversion,to improve the Raman efficiency and output power.An LBO crystal cut for critical phase matching at room temperature is selected and used as a nonlinear optical crystal for realizing the frequency doubling of second-Stokes wave.Its phase matching angle(θ=86.0°,φ=0°)is very close to the non-critical phase matching angle and has a small walk-off angle,which is beneficial to the realizing of the high conversion efficiency of frequency doubling.In the experiment,the beam waist position of the pump light and the repetition frequency of the acousto-optic Q-switcher are optimized.Under an incident pump power of 14.2 W and a repetition frequency of 60 kHz,the highest average output power of 1.63 W and conversion efficiency of 11.5%are obtained for the 657 nm red laser emission.The pulse width of 657 nm red light is 11.5 ns at the maximum output power,which is much narrower than that generated by frequency doubling of ordinary neodymium-doped laser at a waveband of 1.3μm.The result shows that the frequency doubling of the acousto-optic Q-switched Nd:YVO_(4)cascaded self-Ramanlaser can take advantage of the pulse-width compression characteristics of Raman process to achieve a narrower pulse-width red light laser output.