高功率光纤激光器谱合成系统的输出特性分析

Analysis of the Output Characteristics of High-Power Fiber Lasers after Spectral Beam Combination

建立了用光热折变无机玻璃反射式体布拉格光栅实现高功率光纤激光器谱合成的物理模型,在考虑高功率激光导致的体布拉格光栅表面热形变情况下,将体光栅进行分片处理后,采用有限差分Crank-Nicholson和稀疏矩阵方法,通过反复迭代求解波动方程,数值计算了两束光纤激光经不同形变的体布拉格光栅谱合成后的光强分布、桶中功率和合成效率,并定量分析了光栅形变对合成光束光强分布、桶中功率和合成效率的影响。研究结果表明,高功率激光导致的体布拉格光栅表面的热形变不仅会导致合成光束的光束质量变差,而且还会引起谱合成系统合成效率的迅速下降。

The propagation model for the spectral combining （VBG） in the photo-thermal refractive （PTR） glass is built. system of fiber laser beams by the volume Bragg grating Considering the surface distortion of the VBG by high- power lasers, the VBG is dealt with by splitting into slice and the wave equation is calculated iteratively by using the finite-different Grank-Nicholson and sparse matrix methods. The intensity distribution, the combination efficiency and the power in the bucket of two fiber laser beams after spectral beam combination by the VBG with different deformations are simulated numerically. The thermal deformation effect of the VBG on the intensity distributions, the combination efficiency and the power in the bucket of the combined beam is analyzed quantitatively. The results show that the surface distortion of the VBG due to high-power lasers not only degrades the beam quality of the combined beam, but also decreases the combination efficiency of the spectral beam combining system dramatically.