Highly tolerant tunable waveguide polarization rotator scheme

Integrated polarization rotators are known to exhibit stringent fabrication tolerances, which severely handicap their practical application. Here we present a general polarization rotator scheme that enables both the compensation of fabrication errors and wavelength tunability. The scheme is described analytically, and a condition for perfect polarization conversion is established. Simulations of a silicon-on-insulator polarization rotator show polarization extinction ratios in excess of 40  dB even in the presence of large fabrication errors that in a conventional rotator configuration degrade the extinction ratio to below 5  dB. Additionally, wavelength tuning over ±30  nm is shown.