高稳定紧凑型内腔连续光参量振荡器

为了改善内腔连续光参量振荡器（IC-OPO）输出功率不稳定，弛豫振荡严重等问题，对IC-OPO进行了改进:（1）采用热透镜补偿设计，改善模式匹配；（2）使用光阑限模，抑制高阶模振荡；（3）在腔内加入KTP晶体，利用二次谐波产生（SHG）过程的非线性损耗抑制弛豫振荡。通过改进，获得了稳定的紧凑型2.2~4.2 m的可调谐连续波中红外光源。输出功率波动标准偏差（RMS）0.52%，峰值波动范围1.8%，光束质量因子M2=1.72，弛豫振荡得到有效抑制。当腔内不加入KTP晶体时，阈值（808 nm）仅为1.5 W。据笔者所知，该阈值为国内相关工作报道中的最低值。

Highly stable compact intra-cavity continuous-wave optical parametric oscillator

An Intra-cavity Continuous-Wave Optical Parametric Oscillator(IC-OPO) was developed in order to resolve problems inherent in IC-OPO such as instability of output power, long-lived bursts of relaxation-oscillations, etc. First, compensative design of thermal lens effect was devised to improve pattern matching. Second, an aperture slot was used to suppress the oscillations of high-order transverse mode. Finally, by placing a KTP crystal in the cavity for the purpose of SHG, the relaxation oscillation was suppressed by nonlinear loss. After these improvements, the compact tunable infrared to mid-infrared(2.2-4.2 m) continuous source with high-stability was obtained. The amplitude stability of output power is 0.52%(RMS) and peak-to-peak amplitude stability is less than 1.8%. The beam quality M2 is 1.72. Especially, a series of observations show that the relaxation-oscillation is suppressed effectively. Without KTP crystal, the threshold (808 nm) is as low as 1.5 W.