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

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 μm, 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.