Ultrahigh extinction ratio and ultra-low insertion loss silicon TE polarizer covering 1260–1675 nm bandwidth

Abstract

An ultra-broadband TE polarizer with outstanding performance is proposed and demonstrated on a 220 nm-thick silicon-on-insulator platform. The proposed TE polarizer consists of six cascaded directional couplers assisted by subwavelength grating (SWG) structures and two Euler bends. The SWG is introduced to control the coupling strength of the fundamental TE and TM modes. Simulations show that our proposed TE polarizer possesses ultra-low insertion loss (IL < 0.3 dB) for the fundamental TE mode and an ultrahigh polarization extinction ratio (PER > 35 dB) for the fundamental TM mode covering all communication bands from 1260 nm to 1675 nm. The experimental results show that the fabricated TE polarizer has excellent performance of IL < 0.6 dB and PER > 35 dB over a 210 nm bandwidth, which is limited by the measurement equipment. To the best of our knowledge, our proposed TE polarizer is the first single-etched all-silicon TE polarizer with such high PER covering all communication bands.