Tunable omnidirectional reflection bands and defect modes of a one-dimensional photonic band gap structure with liquid crystals

We have theoretically investigated the tunability of the omnidirectional re flection band (ORB) of a one-dimensional (1D) photonic crystal (PC) consist ing of alternating isotropic dielectric and nematic liquid crystal layers b y an external electric field. The width of the ORB becomes wide as the exte rnal voltage increases, but the center frequency is changed little. The fre quency of the defect mode created by inserting a layer of liquid crystals i nto a 1D dielectric PC is also found to be tunable by the application of ex ternal voltage. These properties can be applied to tunable optical filters or optical switches. (C) 2001 American Institute of Physics.