Nano-plasmonic chirped metal-stripes polarimeter for dual-band infrared detection

Abstract

A novel chirped metal structure (CMS) is developed for polarimetric enhanced detection of both mid-wave (MW) (3-5 μm) and long-wave (LW) infrared (IR) wavelength bands (8-14 μm). The nano-scale structure consists of parallel sub-wavelength chirped-width stripes together with graded-width separating gaps. The CMS allows plasmonically enhanced polarisation-sensitive absorption of dual-bands simultaneously in underneath IR detection device. The finite-difference-time-domain method is utilised to numerically evaluate gold CMS structure on an IR detector. Simulations show an excellent performance with high plasmonic absorption enhancement and polarisation extinction-ratio over the continuous wavelength range 3-14 μm. The maximum recorded extinction-ratios are 2900:1 and 400:1 in the LW and MW bands, respectively. The maximum estimated plasmonic absorption enhancements for TM-polarisation in the LW and MW bands are 96 and 16%, respectively. The suppression of TE-polarisation absorption is almost 100% over both bands.