Polarization-insensitive silicon nitride Mach-Zehnder lattice wavelength demultiplexers for CWDM in the O-band

Polarization-insensitive silicon nitride (SiN) 4-channel wavelength (de)multiplexers based on Mach-Zehnder interferometer lattice filters for coarse wavelength division multiplexing (CWDM) in the O-band are demonstrated in a SiN-on-silicon photonic platform. For the best-performing device, the insertion loss was < 2.8 dB, the inter-channel crosstalk was < -11.5 dB for a polarization scrambled input, and the passband shift between the orthogonal polarizations was < 1.5 nm. Across the 200mm wafer, the die-averaged insertion loss and maximum crosstalk were 3.1 dB and -10.6 dB, respectively. The higher-than-expected crosstalk was due to dimensional variations. This work shows the potential of SiN photonic circuits for CWDM without polarization diversity.