Low-Loss and Broadband 2 x 2 Polarization Beam Splitter Based on Silicon Nitride Platform

A low-loss and broadband 2 x 2 Mach-Zehnder interferometer-based polarization beam splitter (PBS) is proposed and experimentally demonstrated on the silicon nitride platform. The device is realized by using a 27.7-mu m-long phase control section, which consists of two arms with different widths to separate TE and TM polarized lights by providing different phase changes. Furthermore, a compact asymmetric 3-dB directional coupler with a parallel-coupling length of only 1.2 mu m is proposed to support polarization independent operation and reduce the device length. The measurement results show that the proposed PBS has a minimum insertion loss of 0.13 dB for the TE polarization and 0.34 dB for the TM polarization. The extinction ratio is over 20 dB throughout the measured band from 1530 to 1610 nm for the TE polarization, and it is higher than 20 dB over the entire C-band for the TM polarization.