Efficient and broadband polarization rotator using horizontal slot waveguide for silicon photonics

We report an efficient and low-loss polarization rotator based on mode evolution using horizontal slot waveguide. The device is fabricated using complementary metal–oxide–semiconductor compatible processes, which allows monolithic integration with active drive electronics and other photonic components. A rotator fabricated with 100 μm transition length provides a high extinction ratio >14 dB for both transverse-magnetic (TM)-transverse-electric (TE) and TE-TM rotation. The excess loss of the device is <1 dB for both rotations as etching of the bottom Si waveguide is prevented. The device also exhibits a uniform rotation response over C+L band wavelength range of 1530-1600 nm.