Extraordinary Optical Transmission and Extinction in a Terahertz Wire-Grid Polarizer

A THz wire grid polarizer is simulated and demonstrated consisting of 40-μm periodic aluminum strips mounted on a polycarbonate substrate with a variable metal-to-gap ratio. Full-wave numerical simulations were performed from 100 GHz to 550 GHz predicting that the transmission in perpendicular (parallel) polarization is much higher (lower) than that predicted by geometric optics, leading to a very high extinction ratio of ∼60 dB between 100 and 550 GHz when the gaps become very small (\u3c5 \u3eμm). This behavior is confirmed qualitatively in experiments between 100 and 530 GHz where extinction ratios exceeding 40 dB are achieved. These results are explained physically as an electromagnetic concentration effect in the gaps consistent with plasmonic-like behavior. The effect depends critically on gap width and weakly on frequency