title: Polarization-independent tunable optical filters using bilayer polarization gratings.
abstract: We demonstrate a polarization-independent tunable optical filter based on switchable polarization gratings (PGs) formed using reactive and nonreactive liquid crystals (LCs). PGs are anisotropic diffraction gratings that exhibit unique properties, including a zero-order transmittance that is independent of incident polarization and that can vary from approximately 0% to approximately 100%, depending on wavelength and applied voltage. A stack of several PGs of varying thicknesses combined with an elemental angle filter yields polarization-independent bandpass tuning with minimal loss. We introduce a novel hybrid PG consisting of both reactive and nonreactive LC layers, which allows very thick gratings to be created with thin active LC layers. We demonstrate a tunable optical filter with a peak transmittance of 84% of unpolarized light, a minimum full width at half-maximum of 64 nm, and a maximum tuning range of 140 nm.
authors.affiliation: Department of Electrical and Computer Engineering, North Carolina State University, 2410 Campus Shore Drive, Raleigh, North Carolina 27606, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Nicolescu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Escuti
mesh_terms: D004867:Equipment Design; D050866:Liquid Crystals; D055096:Optical Devices