Optical properties of one-dimensional photonic crystal with a twisted-nematic defect layer.

Spectral properties of an electrically tunable one-dimensional photonic crystal infiltrated with a twisted-nematic liquid crystal (PC/TN) are investigated. Two mesogenic materials with dissimilar optical anisotropies are examined for constituting the central defect layer. With the TN alignment of the defect layer embedded in the dielectric multilayers, the defect modes not only shift with the applied voltage but also switch between two major modes when the linear polarization angle of the incident light is altered. The superposition of the mixed-mode TN (MTN) and the photonic bandgap brings out a tremendous undulation in all range of the transmission spectrum. The defect modes falling at the centers of the MTN spectral humps are allowed to intensely transmit while the others are suppressed. As a result, we propose a monochromatic selector constructed by such a PC/MTN device with electrical tunability.