Finite-element simulation and design of a high-extinction-ratio THz wire-grid polarizer

Abstract

A THz wire grid polarizer was simulated, designed, and demonstrated. The polarizer consists of 40-micron periodic aluminum strips mounted on a polycarbonate substrate. Finite element numerical simulations were performed from 100 GHz to 550 GHz. The results of these simulations predicted that the transmission in perpendicular polarization would be much higher than that predicted by geometric optics, leading to a very high extinction ratio of ~ 60 dB at high fill factors (~ 90%). This behavior was qualitatively demonstrated in experiments between 100 and 530 GHz where extinction ratios exceeding 40 dB were achieved. These results are explained physically as an electromagnetic field concentration effect in the gaps characteristic of plasmonic-like behavior. The effect is strongly dependent on gap width and weakly dependent on frequency.