808nm与888nm抽运Nd：YVO4热效应分析

Thermal Analysis of Nd:YVO_4 Pumped by 808 nm and 888 nm

根据Nd:YVO4晶体对808 nm和888 nm波长抽运光吸收特性的差异,模拟了两种波长抽运下晶体的温度分布、应力分布以及当抽运光在a轴和c轴上的偏振分量变化时,晶体在两种波长抽运下温度分布以及热焦距的变化。模拟结果表明,888 nm抽运下,Nd:YVO4晶体在径向温度梯度大幅度减小,晶体温度应力值远小于808 nm抽运;并且Nd:YVO4的a轴与c轴对888 nm光吸收系数相同,使得晶体的吸收不受抽运光偏振变化的影响,从而使得谐振腔和输出的激光功率更加稳定。采用888 nm抽运,是降低Nd:YVO4晶体热效应和提高Nd:YVO4激光器输出功率的有效途径之一。

Temperature and stress distribution of Nd：YVO4 crystal are simulated according to the difference of optical absorption properties of Nd：YVO4 crystals pumped by 808 nm and 888 nm,respectively.The changes of crystal temperature distribution and thermal focal length are also simulated when the pumping beam polarization components in a-axis and c-axis are changed.From simulation results,the crystal temperature gradient with 888 nm pump-wavelength is one sixth than that of 808 nm and the crystal temperature stress value is much less than that of 808 nm pump-wavelength.The resonator and output power are not affected by the change of pumping beam＇s polarization because the light absorption coefficients on a-axis and c-axis of Nd：YVO4 are the same when pump wavelength is 888 nm.This is one of the effective ways to reduce Nd：YVO4 crystals thermal effect and increase Nd：YVO4 laser power with 888 nm pump-wavelength.