Spectral control in the liquid crystal tunable filters

A liquid crystal is used as an electro-optical device with the advantages of low voltage driving, low power consumption, and thin flatness by utilizing its refractive index anisotropy (birefringence). In this research, a liquid crystal tunable filter (LCTF) with control of a main peak wavelength <i>λ</i>₀ and a full-width Δ<i>λ</i> at half maximum is developed. The device contains two stacking liquid crystal layers with different wavelength dependences of birefringence Δ<i>n</i> with their optical axes perpendicular to each other and controlling the light wavenumbers in a complementary manner (S-ECB).