为了获得高光束质量的脉冲固体激光输出,研究了高斯非稳腔固体激光器的模式分布。运用边界有限元法将谐振腔内光场衍射积分方程转化成矩阵方程组, 模拟分析了平凸高斯非稳腔内光阑位置、孔径大小以及高斯镜参数对输出光束模式的影响。基于理论模拟结果对激光器结构参数进行了优化, 分别测量了腔内不同光阑位置和孔径下的激光器输出光束振幅及模式分布情况。在光阑半径为1 mm、光阑距高斯镜为150 mm、泵浦电压为900 V的实验条件下, 光束质量M2x=19、M2y=23, 激光最大输出能量为280 mJ的高光束质量激光输出。实验结果表明, 在腔内加入选模光阑以及优化高斯镜参数可以进一步改善腔内模式分布, 获得高光束质量激光输出, 这与理论模拟结果基本相符。

In order to obtain high beam quality pulsed solid laser output, the distribution mode of the Gaussian unstable resonator was studied. The boundary finite element method was used to transform the integral equation of the diffraction of the light field in the cavity into a matrix equation. According to a theoretical simulation, the effects of the aperture position, the size of aperture and the parameters of the Gaussian mirror on the amplitude of the output beam in a plane-convex Gaussian unstability cavity were analyzed. Based on the results of the theoretical simulation, the optical parameters of the laser were optimized. The distribution of amplitude and mode of output beam under different positions and aperture sizes were measured in this experiment. When the radius of the aperture was 1mm, the aperture was 150 mm from the Gaussian mirror, the pump voltage was 900 V, the values of M2 in the x and y directions were respectively 19 and 23, and the maximum output energy of the laser was 280 mJ. The experimental results show that the addition of an aperture and the optimization of the parameters of the Gaussian mirror could improve the distribution of intracavity mode and produce high quality beam output, which agrees with the results of the theoretical simulation.