Design of Switchable Guided-Mode Resonant Filters in Zenithal-Bistable Liquid-Crystal Gratings

An electro-optically switchable infrared filter based on guided-mode resonances in a zenithal-bistable liquid-crystal grating is designed and theoretically investigated. By proper selection of the material and geometrical parameters, it is shown that the grating can switch between transparent and narrowband filtering operation. Switching times of few milliseconds are predicted owing to the employment of a dual-frequency nematic liquid crystal as the addressable material. The tunability of the resonant wavelength is also studied following two approaches, namely, the adjustment of the angle of incidence of the impinging lightwave and the liquid-crystal tuning by the electro-optic effect.