Polarization-insensitive silicon oxynitride Mach-Zehnder interferometers for LAN-WDM

A polarization-insensitive four-channel wavelength-division multiplexing (WDM) (de)multiplexer based on Mach-Zehnder interferometers is proposed and demonstrated. Polarization insensitivity can be achieved by utilizing the square waveguides and bend directional couplers (bend DCs) based on silicon oxynitride (SiON) waveguides. The WDM (de)multiplexer has an 800GHz spacing for LAN-WDM application. Two stages of cascaded MZIs are utilized to achieve a four-channel spectral response. For the realized WDM (de)multiplexer with Gaussian-like passbands, the polarization-dependent losses (PDL) are less than 0.7dB for all 1-dB passbands. The insertion losses are <~ 3dB and the crosstalk is <~ -12dB for both TE and TM polarizations at channel central wavelengths.