A novel approach to distributed feedback in liquid crystals

Nematic liquid crystals (NLC) consist of dielectrically anisotropic molecules in a fluid state; under proper anchoring at the boundaries of a cell, these elongated molecules tend to align, exhibiting a degree of orientational order and behaving as an optically birefringent uniaxial. NLC are transparent from the ultraviolet to the mid-infrared and exhibit a large electro-optic response. For these reasons, a number of configurations have been investigated for guided-wave devices in optical signal processing, with particular attention to voltage-tunable geometries and, among them, Bragg resonant structures. In this Communication we analyze a novel electro-optic distributed feedback waveguide encompassing full adjustability in degree of confinement and Bragg resonance wavelength using an externally applied voltage. We propose and numerically test the structure, demonstrating its operation as a wavelength-selective reflector and tunable drop-multiplexer.