Ultrasmall Si-nanowire-based polarization rotator

A polarization rotator based on asymmetrical Si nanowires is presented and optimized for high polarization rotation efficiency (almost 100%). The present polarization rotator has a very small conversion length (~10 μm) and consequently becomes very compact. The analysis of the wavelength dependence shows the present polarization rotator has a broad bandwidth (~120 nm) for high conversion efficiency (>97%). The tolerance to various fabrication errors is also numerically studied. To compensate the fabrication error, a postcompensation method is introduced by modifying the refractive index of the up-cladding.