High Efficiency Polarization-Independent Slanted Grating for RGB Bands

We proposed a slanted grating suitable for RGB bands which is polarization-independent and has a high diffraction efficiency of −1st order under normal incidence. We used Rigorous Coupled Wave Analysis (RCWA)and simulated annealing (SA) algorithm to optimize grating parameters and the simulation results showed that the -1st order diffraction efficiency of TE and TM polarizations in the RGB band under normal incidence both exceed 83%, which can be used for three-dimensional (3D) display. Then, by using rigorous modal theory, simplified modal method (SMM), and mode coupling theory, we analyzed the reason for the high-efficiency of −1st order diffracted light. Moreover, the numerical simulation of the simplified modal method is consistent with the rigorous coupled wave analysis of the small slanted angle grating. Therefore, the simplified modal method can be used for small slanted angle gratings as its physical analysis proved that small slanted angle gratings and rectangular gratings have equivalence to a certain extent. This work not only presents numerical solutions of slanted grating with high efficiencies over a wide range of RGB wavelength, but also enables us to have a deeper understanding of the diffraction of slanted gratings.