Wang Hanbin, Song Yinglin, Yang Yifeng, Xian Yuqiao, You Yang, Liu Meizhong, Yuan Zhijun, Wei Taihui, He Bing, Zhou Jun
Opt Express. 2020 Oct 26;28(22):33334-33345. doi: 10.1364/OE.408832.
The multilayer dielectric (MLD) grating is a critical device for combining multiple laser beams into a single beam in a spectral beam combining (SBC) system. We established a theoretical thermal deformation model of the laser-irradiated MLD grating. Thermal deformation on the surface of the grating is simulated according to a series of parameters including the laser irradiation time, laser power density, and substrate size. To verify the model, we exposed a 960 l/mm, 50×50×1.5 mm grating to a laser power density of 3.61 kW/cm and observed the temperature change. We used a Twyman-Green interferometer to measure the interference fringes on the grating surface. Based on the Fourier-transform method and a Zernike polynomial fitting method, the real-time grating surface profile is reconstructed. The results show that substrate thickness increase or area decrease can reduce thermal deformation, the average decreases are 18.3% and 19.9%, respectively. The discussion and analysis of the grating thermal deformation are potentially valuable for designing grating to decrease the thermal deformation and improve the combined beam quality of a SBC system.
多层介质（MLD）光栅是光谱合束（SBC）系统中将多束激光合成为单束激光的关键器件。我们建立了激光辐照MLD光栅的理论热变形模型。根据激光辐照时间、激光功率密度和基底尺寸等一系列参数模拟了光栅表面的热变形。为验证该模型，我们将一块960 l/mm、50×50×1.5 mm的光栅置于3.61 kW/cm的激光功率密度下，并观测了温度变化。我们使用泰曼-格林干涉仪测量光栅表面的干涉条纹。基于傅里叶变换法和泽尼克多项式拟合方法，重建了光栅表面的实时轮廓。结果表明，增加基底厚度或减小面积可降低热变形，平均降幅分别为18.3%和19.9%。对光栅热变形的讨论和分析对于设计光栅以减少热变形和提高SBC系统的合束光束质量具有潜在价值。
