Polarization-Independent Wavelength Demultiplexer Based on Single Etched Diffraction Grating Device

Abstract

Polarization-compatible receivers are indispensable in transceivers used for wavelength division multiplexing (WDM) optical communications, as light polarization is unpredictable after transmission through network fibers. However, the strong waveguide birefringence makes it difficult to realize a polarization-independent wavelength demultiplexer in a silicon photonic (SiPh) receiver. Here, we utilized the birefringence effect for simultaneously demultiplexing wavelengths and polarizations, and experimentally demonstrated a novel polarization-independent wavelength demultiplexer with a single device on a SiPh platform. The principle was validated on an etched diffraction grating (EDG), which successfully split the arbitrarily polarized light containing four wavelengths into eight channels with single-polarization and single-wavelength signals. Polarization-dependent losses of 0.5-1.8 dB, minimum insertion loss of 0.5 dB, and crosstalks lower than -30 dB were experimentally measured. Thus, a promising general solution was developed for implementing polarization-independent WDM receivers and other polarization-independent devices on SiPh and other platforms with birefringent waveguide devices.