Low-index cladded wire grating as broadband polarizing beam splitter

Abstract

A sandwich structure including subwavelength grating and low-index thin film as a broadband polarizing beam splitter (BPBS) is demonstrated. The BPBS is studied by using the rigorous coupled-wave analysis (RCWA) numerical scheme. The low-index thin-film with optimum thickness forms between the silicon substrate and the subwavelength grating. While the thickness of low-index thin film is larger than 0.6 m, the reflectivity of TE wave is larger than 0.95 in the wavelength region [1.29 m, 1.66 m] under the normal incidence. In this region, the reflectivity of TM wave is low. Meanwhile, it is also found that while the thickness of low-index thin film rise to 0.9 m, the extinction ratio of TM polarization is less than 0.047 in the wavelength region [1.35 m, 1.48 m]. Therefore, the designed sandwich structure consisted of subwavelength grating, low-index thin film and silicon substrate can be used as broadband polarizing beam splitter.