Compact polarization rotator on silicon for polarization-diversified circuits

Abstract

We demonstrate a polarization rotator based on adiabatic mode evolution on silicon for polarization-diversified circuits. The rotator has a device length of $420\mathrm{\mu m}$, a polarization-conversion efficiency of more than 90%, and an insertion loss less than $1\mathrm{dB}$ for a wavelength range of $80\mathrm{nm}$. Combining the rotator with a compact, broadband polarization beam splitter based on cascaded directional couplers enhances the polarization conversion extinction ratio to over $30\mathrm{dB}$ with less than $1.5\mathrm{dB}$ total insertion loss over a $60\mathrm{nm}$ spectral range.