二极管激光光栅-外腔光谱合成技术模拟研究

Simulation of spectrally beam combined diode laser based on grating-cavity

光栅-外腔光谱合成效率主要由激光器和外腔的耦合效率决定。从衍射积分方程出发,建立了存在离轴像差情况下耦合效率模型,分析了光谱合成系统参数对耦合效率的影响。结果表明:当离轴距离增加、横模阶次增大、模场半径减小、阵列平面或光栅平面偏离焦平面时,耦合效率随之下降;光栅倾角和光栅平面-耦合输出镜距离对耦合效率影响甚微。对采用焦距为500 mm的对称双球面透镜,长度为10 mm二极管激光阵列的系统,快轴方向模场半径应大于0.15 mm,慢轴方向模场半径应大于20μm,阵列平面位置误差应控制在±0.5 mm内,光栅平面位置误差应控制在±0.2 mm内。

The efficiency of spectral beam combining based on grating-cavity mostly depends on the coupling efficiency between emitter and cavity. Based on the diffraction integral equation, the coupling efficiency model with abaxial aberration is established. Then, the effect of the system parameters on the coupling efficiency is analyzed quantitatively. The results show that the coupling efficiency decreases when abaxial distance or the order of mode increases, or when mode field radius increases, or when the grating plane or the array plane deviates farther from the focal plane. The grating＇s tilt angle and the distance between the grating plane and the output coupling mirror have few influence on the coupling efficiency. For the system with bi-convex lens of 500 mm focal length and 10 mm array, the mode field radius should be more than 0.15 mm and 20 μm in fast axis（direction） and slow axls（direction） respectively, the deviation of array plane should be no more than 0.5 mm, and the deviation of grating plane should be no more than 0.2 mm.