High extinction ratio and low loss polarization beam splitter based on multimode interference for PICs

A polarization beam splitter (PBS) with a high extinction ratio that is based on multimode interference (MMI) is proposed and experimentally demonstrated on a silicon-on-insulator platform. The PBS is designed using cascaded MMI to enhance the extinction ratio (ER) and minimize insertion loss (IL) compared to a conventional MMI structure. The proposed device has a high extinction ratio (22.3 dB for TE and 25.6 dB for TM) and a low insertion loss (0.7 dB for TE and 0.1 dB for TM) at a wavelength of 1550 nm while the device supports a broad bandwidth of 60 nm ( E R > 16 d B ) for both polarizations over a wavelength between 1520–1580 nm. Moreover, the eigenmode expansion method shows that the device has a large fabrication tolerance of an MMI width ± 40 n m and a length ± 1500 n m . The proposed PBS can be used in on-chip silicon photonic integrated circuits for polarization division multiplexing.