Asymmetric Silicon Slot-Waveguide-Assisted Polarizing Beam Splitter

Abstract

A silicon polarizing beam splitter is designed and fabricated based on an asymmetric slot waveguide structure without adopting additional strip-slot waveguide mode converters. The asymmetric slot waveguide consists of a 150-nm-wide and a 350-nm-wide nanowires with a slot of 100 nm, which can realize a transverse magnetic light cross-coupling with a 392-nm-wide strip waveguide, while little transverse electric light coupling can happen. The fabricated device has a coupling length of $\sim 18~\mu \text{m}$ with a coupling gap spacing of 450 nm, which can achieve a polarization extinction ratio (PER) of $\sim 14$ and 25 dB at the bar and cross ports, respectively. Low insertion loss is realized, while more than 10-dB PER can be obtained over the wavelength range of 1520–1576 nm. The device performance could be further improved with the fine optimization of device structure parameters and fabrication process.