Optically tunable narrowband filter using liquid crystal defect in 1-D photonic crystal

Based on the theory of liquid crystal continuum, the tuning principle of one dimensional Si/SiO₂ photonic crystal embedded in a nematic liquid crystal as a defect layer is analyzed and the relationship between applied voltage and tuning range is studied numerically by using transmission matrix method. The structure parameters of a tunable filter with narrow bandwidth and broad tuning range are determined through simulation computation. The computation results show that the tuning range achieve 100.8 nm between 1600.6 nm and 1499.8 nm when the applied voltage varies from 0.955 V threshold to 5 V saturation. The obtained tuning range covers telecommunication C band and almost S and L band. FWHMs (full width at half maximum) of the transmission peaks are between 0.074 nm and 0.090 nm, and the differences of bandwidths less than 17.8 percent.