Simulation of bilayer gratings: exploring the impact of structural parameters on applications

This research delves into the influence of structural parameters on the performance of bilayer gratings, a critical factor in photonic applications. Employing the finite-difference time-domain (FDTD) method, we scrutinized the impact of duty cycle, period, and thickness on key metrics such as diffraction efficiency and diffraction angle. Our findings indicated that thickness and duty cycle of gratings played crucial roles in optimizing diffraction efficiency while larger gratings’ period decreases diffraction angle. We further simulated a misaligned bilayer gratings and demonstrated diffraction-based overlay measurement, tuning thickness and duty cycle to observe their influence on overlay measurement precision.