High extinction ratio polarization beam splitter with multimode interference coupler on SOI

A high extinction ratio polarization beam splitter based on multimode interference coupler has been obtained on silicon-on-insulator. The multimode interference coupler is designed by using quasi-state imaging theory, and fabricated with E-beam lithography and induced coupled plasma etching technology. The device has footprint of 8.16 μm×1034 μm. The measured extinction ratios remain 45 dB for TE mode and 23 dB for TM mode at wavelength of 1.55 μm. The extinction ratio of more than 20 dB for TE mode and 15 dB for TM mode is observed covering the whole C-band.