Analysis of thermal effects in micro region of non-polarizing grating under high power laser irradiation using RCWA

We analyzed the thermal effect of non-polarizing grating for high power laser beam combining using RCWA (Rigorous Coupled-Wave Analysis). First, We investigated design conditions of rectangular dielectric grating for high efficiency and polarization independence from thin film stack, matched layer thickness, duty cycles, and grating height based on SiO₂, Ta₂O₅ and HfO₂. Then, we calculated the -1st order diffraction efficiency by wavelength range and incidence angle of input beam. Finally, we estimated the electric field distribution of TE(Ey) and TM(Ex) mode and analyzed the temperature distribution. Among several design conditions, we optimized the design of dielectric grating with high efficiency, polarization independence, and minimum temperature distribution. As a results, the thermally stable grating design will be used for high power laser beam combining.