Tunable omni-directional mirror based on one-dimensional photonic structure using twisted nematic liquid crystal: the...

We present the tunability of the omnidirectional band gap (OBG) in a one-dimensional photonic structure consisting of N nematic liquid-crystal slabs in a twisted configuration. It is alternated by N isotropic dielectric layers by a dc electric field aligned along the periodicity axis. We consider the general case for which arbitrary anchoring of the nematic at the boundaries is taken into account. The threshold electric field for which the OBG is created decreases as the anchoring strength diminishes. The width of this band gets larger as the electric field increases and its center frequency is modified slightly.