Considering the influences of temperature on refractive index and grating period, the paper studies the relations between quasi-phase-matched second harmonic generation(SHG) conversion efficiency and temperature, and analyzes the influ-ences of laser thermal effect on quasi-phase-matched SHG. The temperature distribution and SHG conversion efficiency under the influences of laser thermal effect inside periodically poled lithium niobate(PPLN) crystal are calculated by finite element method. The results show that, for fundamental wave of different power, the temperature distributions and the refractive index distribu-tions on crystal sections along the direction of light are different, and so are the SHG conversion efficiency distributions on the exit facet of crystal. With the power of fundamental wave increasing, the total temperature and refractive index of crystal increase. Moreover, the laser thermal effect does have some effects on the conversion efficiency of SHG in PPLN crystal.%从准相位失配关系出发,研究了PPLN晶体倍频效率与温度的关系,针对温度对折射率与极化周期的影响,分析了激光热效应对准相位匹配系统谐波转换过程的影响.采用有限元分析法计算了PPLN材料内部温度分布状况,并对热效应影响下晶体内部倍频效率变化情况进行了计算.计算结果表明:在不同基频光功率密度下,在倍频过程中晶体温度及通光方向截面折射率的分布不同,在倍频晶体出射面倍频效率的分布也不同；随基频光功率密度增大,晶体整体温度与折射率增大,出射端面倍频效率分布随基频光功率密度变化而变化；与理想条件倍频系统相比,激光热效应对晶体倍频效率有一定的影响.
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