Ultra-compact and highly efficient polarization rotator utilizing multi-mode waveguides

An ultra-compact and highly efficient polarization rotator is proposed and experimentally realized on the silicon-on-insulator (SOI) platform. The polarization rotation (TM0-TE1) process is obtained by utilizing a straight multi-mode waveguide, while the mode conversion (TE1-TE0) process is realized by a bent multi-mode waveguide. For the proposed structure, only one etching step is required for the fabrication. The measured extinction ratio and insertion loss at the central wavelength are 19.8 and 0.86 dB, which agree well with the simulations.