Multilayer subwavelength metallic grating as a high performance polarizer in infrared short wavelengths

This paper addresses the burning issue of both low transmission and limited extinction ratio in polarizers based on a single layer subwavelength grating in short infrared wavelengths. In this work, an alternative polarizer with four layers of subwavelength gratings in gold, encapsulated in silica, was developed. Systematic simulations using the finite-difference time-domain (FDTD) method were carried out in designing the polarizer for the structural dimensions to ensure the highest transmission and the highest extinction ratio. The designed polarizer was fabricated by using the high-precision registration technique in electron beam lithography (EBL), followed by metallization of golden gratings and plasma chemical vapor deposition of silica. Optic measurement shows both high transmission (40% anti-reflection effect) and high extinction ratio (∼27 dB) in the wavelengths of 1100-1600 nm be achieved. The developed multilayer subwavelength grating in Au provides us with the promising solution for high transmittance as well as high extinction ratios of grating based polarizers.