Tunable structure of nanowire-grid polarizer for deep ultraviolet region

Abstract

As the performance of nanowire-grid polarizer is determined by the characteristic size of nanowire, the polarizer for full ultraviolet (UV) region requires the characteristic size less than 50 nm, which is challengeable to the current fabrication level. In this letter, two pieces of nanowire-grid polarizers sandwiching a layer of polymer-dispersed liquid crystal (PDLC) was proposed as a tunable structure of nanowire-grid polarizer for high performance in deep ultraviolet region with 100 nm of nanowire period. In this structure, the transmittance of transverse electric (TE) mode (TTE) and transverse magnetic (TM) mode (TTM), and also the transmission extinction ratio (Ex) could be tuned by the optical path of the PDLC layer. Assuming the refractive index of PDLC layer could be varied from 1.5 to 1.6 as its applied voltage changed from saturation voltage to zero, we calculated the TTM and Ex, which varies periodically as the PDLC layer refractive index increasing. For a given incident wavelength, the maximums of TTM and Ex could be attained easily by tuning the applied voltage on PDLC layer. The simulation results show that the tunable structure has a short starting wavelength than that of single layer and double-layer structure nanowire-grid polarizer at a given transmission or extinction requirement with same characteristic size of nanowire, because of the constructive interference of TM polarization and the destructive interference of TE polarization in these two layers of nanowire, similar to a Fabry-Perot cavity, which makes it excellent to be applied in deep UV region.