Robust silicon waveguide polarization rotator with an amorphous silicon overlayer

摘要

We propose a robust polarization rotator based on the mode-evolution mechanism.The polarization rotation in a silicon wire waveguide is achieved by forming an amorphoussilicon (a-Si) overlayer and an SiO\u2082 spacer on top of the waveguide. A strip pattern of aconstant width is designed to be etched through the overlayer at a specific angle with respectto the Si waveguide. The asymmetry in the a-Si overlayer affects the waveguide mode byrotating the modal axis. This polarization rotator design is amenable to comparatively simplefabrication compatible with standard silicon photonic processing for integration. The length ofthe rotation section is 17 \u3bcm, and the broadband operation is achieved with a rotation efficiencyhigher than 90% for a wavelength range exceeding 135 nm. A maximum polarizationrotation efficiency of 99.5% is predicted by calculation.