Ultrashort and Low-Loss Polarization Rotators Utilizing Hybrid Plasmonic-Dielectric Couplers

Abstract

In this letter, we propose a hybrid plasmonic polarization rotator (PR) utilizing asymmetrical directional coupling between a hybrid plasmonic waveguide and a strip Si dielectric waveguide (DW), which features ultracompact size, low insertion loss (IL), and silicon-on-insulator compatibility. The coupling length is only 11.2 $\mu $ m, much shorter than the PRs based on asymmetrical directional coupling between two strip DWs on the same silicon core layer with the same coupling gap. The presented PR shows a high polarization conversion efficiency (PCE) of 99.9% at 1550 nm with an IL of 0.136 dB, which is extremely low in the reported plasmonic PRs. In addition, it yields the PCE better than 96% and the IL lower than 0.42 dB over a bandwidth of 60 nm.