An Ultra-Broadband Design of TM-Pass/TE-Stop Polarizer Based on Multistage Bragg Gratings

Abstract

In this paper, a multistage Bragg grating with various kinds of periods is introduced in the design of a reflection-based TM-pass/TE-stop polarizer. The cascade grating sections reflect a wide wavelength range of the TE polarization state. Additionally, on the other hand, the TM polarization state always passes through the waveguide. Such a design facilitates the polarizer working bandwidth, which is defined as the wavelength range with an extinction ratio of greater than 20 dB, and can reach 231 nm using only three grating sections. Meanwhile, the incision loss is always less than 0.42 dB over the working wavelength band. Furthermore, if a slightly higher loss is permitted, the polarizer working bandwidth can be extended to further than 310 nm using five grating sections.