Angular Tolerance Enhancement in Guided-Mode Resonance Filters with a Photonic Crystal Slab

Two different triple-layer guided-mode resonance (GMR) filters with photonic crystal (PC) slab structures are designed, and their main optical properties are investigated. It is shown that under normal incidence, the PC slab GMR filters exhibit narrower bandwidth, a more symmetric line shape, and larger angular tolerance, compared with the planar grating GMR filters. The rod-slab type GMR filter works better than the hole-slab one. The resonance wavelength location and the angular tolerance can be tuned by varying the periods. The angular tolerance with narrow bandwidth can be improved by increasing the ratio of the periods in the two crossed directions.