Terahertz Flat-Top Polarization Filter Based on Liquid Crystal Cavities

A terahertz (THz) polarization filter based on liquid crystal cavities is designed. The P and S polarized light are both transmitted and the minimum transmittance of P and S polarized light at pass-band is higher than 99.5%. The P polarized light and S polarized light can be both separated distinctly at a small angle. We discuss the influence of each structural parameter on spectral performance, such as rectangle degree, duty cycle, spectral period etc systematically. The results show that the refractive index of the thin-film layers mainly influences the rectangle degrees and duty cycle. The liquid crystal cavities are inversely proportional to the spectral period. The center-frequency tunable characteristics can be realized by changing the incident angle with small angle.