Study on the influence of surface roughness on the diffraction efficiency of two-dimensional gratings

This study investigates the effect of surface roughness on the diffraction efficiency of two-dimensional gratings. Firstly, a roughness model was constructed using FDTD, followed by a significant analysis of the ridge roughness, groove roughness, and sidewall roughness on diffraction efficiency. Then, the impact of each roughness type on diffraction efficiency was studied separately. Results indicate that ridge roughness has a negative impact on diffraction efficiency, whereas groove roughness and sidewall roughness have a positive impact on the diffraction efficiency of two-dimensional gratings. When ridge, groove, and sidewall roughness coexist, diffraction efficiency decreases with an increase in roughness, consistent with previous research. However, under conditions of minimal roughness, diffraction efficiency actually increases. Finally, an experiment was conducted to verify the conclusions. The results of this study have significant reference value for the application and development of precision measurement techniques for gratings.