Color filters featuring high transmission efficiency and broad bandwidth based on resonant waveguide-metallic grating

A one-dimensional transmission color filter based on a resonant waveguide-metallic subwavelength grating was numerically investigated by employing rigorous coupled-wave analysis (RCWA) and genetic algorithm (GA). The hybrid numerical method is used to determine the optimal parameters (the grating period, filling factor, grating thickness, and waveguide thickness) of two waveguide-grating structures, namely a double-layer resonant waveguide-metallic grating and a triple-layer resonant waveguide-metallic grating. The optical responses of these structures are evaluated and compared in terms of the ideal transmission efficiency aiming at the central wavelengths of 645 nm, 546 nm, and 455 nm of red (R), green (G), and blue (B) lights, respectively, over the visible region (380-780 nm). The results show that the optical performance of the double-layer with silver grating achieves the highest transmission efficiency of 82% (R), 81% (G), and 66% (B); and the largest bandwidth of about 125 nm (R), 118 nm (G), and 85 nm (B). Compared with existing color filters, the proposed device not only obtains a higher transmission and broader bandwidth, but it also suppresses redundant spectral peaks and transmission sidebands. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.