Nearly polarization-insensitive angular filters enabled by metal-dielectric photonic crystal in the visible region

Abstract

We report on the design and fabrication of nearly polarization-insensitive angular filters, which have been developed through the optimization of one-dimensional Ag/MgF2 photonic crystals (PCs). We evaluate different initial systems for optimization and compare their results in terms of both the wavelength and angular selectivity. Our findings reveal that relaxing the strict periodic condition of initial photonic crystals with a small number of lattices has enabled improvement in the angular selectivity via Fabry–Perot resonances in dielectric layers, achieving a transmission as high as 81% at normal incidence by optimizing the dielectric layer thickness. The simulation results demonstrate that the transmitted beam through the angular filtering sample at 633 nm has allowable angles within 29° and 33° for TE and TM polarization, respectively, with a transmission over 80% at normal incidence. This proposed and demonstrated angular filter represents what we believe is a novel way to utilize 1D metal-dielectric PCs as polarization-insensitive angular filters, overcoming the main drawback of a low transmission. This angular filter will have significant applications in lighting, beam manipulation, optical coupling, and optical detectors.