利用COMSOL软件建模对光参量振荡器(OPO)进行热分析,发现在大功率抽运下,晶体的中心轴线附近由于吸收参量光,出现较为明显的温度上升。MgO∶PPLN晶体的折射率对温度非常敏感,较小的温升会使参量光产生不可忽略的波前畸变,进而导致光束质量下降。晶体的温升是由参量光的吸收引起的,这样的温升不可避免,大功率OPO/OPA(光参量放大器)的光束质量劣化是必然的。

By modeling with COMSOL software, we carry out the thermal analysis of optical parametric oscillator (OPO). We find that under high pump power, temperature near the central axis of crystal increases due to the absorption of parametric light. Because the refractive index of MgO∶PPLN crystal is very sensitive to temperature, a small temperature rise will cause the non-negligible wavefront distortion of parametric light, which leads to the decrease of beam quality. The temperature rise of crystal is caused by the absorption of parametric light, and such temperature rise is unavoidable. The deterioration of beam quality in high power OPO/OPA (optical parametric amplifier) is inevitable.