Highly efficient and fabrication-tolerant InP polarization rotator-splitter

A highly efficient passive polarization rotator and splitter based on mode-evolution is demonstrated. The device is fabricated on InP substrate with a single etch-step and uses an adiabatic mode-converter and an asymmetric Y-coupler. Despite its simple fabrication process, the device shows a polarization extinction ratio (PER) better than 19 dB over 1520 nm to 1620 nm, thus covering both C- and L-band. Peak values of 24 dB for both TE and TM polarizations are measured. Its fabrication tolerance is large, so that even under a width variation of +/− 200 nm the PER remains above 17 dB over the entire C- and L-band.