绿光泵浦的黄光波段可调谐窄线宽光学参量振荡器

Green pumped yellow wavelength tunable narrow linewidth optical parametric oscillator

为实现波长可调谐的窄线宽黄光波段激光输出,设计搭建了以倍频声光调Q Nd:YAG激光器的532 nm脉冲绿光输出为泵浦源、以II类相位匹配磷酸钛氧钾(KTP)晶体为非线性介质的折叠腔光学参量振荡器(OPO)。首先产生腔内振荡的近红外可调谐闲频光,在此基础上基于LBO晶体I类非临界相位匹配方式对OPO的闲频光进行内腔倍频,得到波长调谐范围587.2~595.2 nm的黄光波段输出。为改善OPO光谱特性,在OPO闲频光谐振腔内插入熔融石英标准具,有效压缩了OPO输出黄光的光谱线宽。绿光泵浦源脉冲重复频率10 kHz、平均功率24.0 W下在波长591.2 nm处获得了最高黄光输出功率2.89 W,光束质量因子M^2=3.4,从532 nm泵浦光到黄光输出的转换效率为12.0%,脉冲宽度37 ns,对应峰值功率7.8 kW。此时黄光光谱半高全宽为0.15 nm,相比未在OPO腔内插入标准具自由运转状态下的光谱得到明显改善。

A pulsed optical parametric oscillator(OPO)was demonstrated for the purpose of wavelength-tunable yellow output with narrow spectral line width.The OPO pumped by the green output of an acousto-optic Qswitched Nd:YAG used a type II phase-matched KTiOPO4(KTP)crystal as the nonlinear gain medium and a folded cavity arrangement.The OPO was designed to have the idler wave tunable in near infrared oscillated in the cavity,which was further frequency doubled to generate the wavelength-tunable yellow output by using a LiB3 O5(LBO)crystal with type I non-critical phase matching scheme.A fused silica etalon was inserted in the idler wave cavity to narrow the idler wave and the resultant yellow spectral line width.The wavelength of the yellow output obtained could be tuned over 587.2-595.2 nm,within which the maximum average output power of2.89 W was obtained at 591.2 nm,under an incident average green pump power of 24.0 W.The beam quality factor M^2 was 3.4.The conversion efficiency from the green pump to the yellow output was 12.0%.The pulse width at the maximum output power was 37 ns,and the peak power was 7.8 kW.The spectral line width of the yellow output was 0.15 nm,which was narrowed effectively compared with that without etalon in the OPO cavity.