腔内多模光束偏心辐射非线性晶体温度场分析

为了解决高功率绿光激光器非线性晶体腔内倍频非均匀温升对谐波转换效率的影响问题,对非线性晶体多模光束腔内倍频温度特性进行了解析研究.依据非线性晶体腔内倍频工作状态特点分析,利用热传导方程得到了非线性晶体腔内基波多模光束偏心辐射温度场的一般解析表达式.结果表明,若偏心辐射到晶体的多模束腰光斑为200μm,谐振腔内多模基波功率为500W,多模基波偏心辐射(偏心度ξ=0.33)KTP晶体内的最高温升为79.80℃,相对于同等条件中心辐射的最高温升83.14℃降低了4.0%;当基波入射非线性晶体偏心度增大时,可有效地降低KTP晶体的最高温升.建立的非线性晶体热分析模型符合绿光激光器的实际需要,对于消除非线性晶体热效应影响、提高激光器谐波转换效率具有指导意义.

Temperature field of nonlinear crystal eccentric-radiated by intra-cavity multi-mode beam

In order to improve the frequency doubling conversion efficiency of nonlinear crystal influenced by non-uniform temperature rise in high power green lasers, the temperature performance of nonlinear crystal with intracavity multi-mode frequency doubling was analytically investigated. According to the actual characteristics of nonlinear crystal with intra-cavity frequency doubling, based on the heat conduction equation, a general analytical expression of temperature field in nonlinear crystal eccentric-radiated by multi-mode fundamental wave was obtained. The result shows that when the waist spot radius of multi-mode light beam is 200μm, the power of fundamental wave is 500W, and the maximum temperature rise of KTP crystal eccentric-radiated (eccentric degree ξ=0.33)by fundamental harmonic is 79.80℃, 4.0% lower than the maximum temperature rise 83.14℃ of KTP crystal center-radiated by fundamental harmonic with other conditions keeping the same. When the radiation eccentricity increases, the maximum temperature rise of KTP crystal can be effectively reduced. The thermal model of nonlinear crystal meets the actual requirement of green lasers, which will play an instructive role in elimination of nonlinear crystal heating effect and improvement of the harmonic conversion efficiency of nonlinear crystal.