A novel polarization rotator based on an asymmetric slot waveguide

A slot-assisted polarization rotator is proposed and analyzed. Through introducing a slot in the channel waveguide yet deviated from the waveguide center, the hybrid modes are excited effectively, which contributes to the mode rotation. However, the excess loss is intrinsically high due to the mode mismatch between the slot waveguide and channel waveguide. Thus, two sections of tapered slot waveguides are inserted in the front and rear slot-channel splices, and the slot tip width and the length are chosen to be 40 nm and 1 μm, resulting in higher transmission and less excess loss. The whole length of the slot waveguide is 52.8 μm including the two tapered sections, and the transmission is higher than 97% at 1550 nm with about 35 dB polarization extinction ratio. The wavelength bandwidth is about 60 nm (1520–1580 nm) with the extinction ratio higher than 12 dB and the excess loss less than 0.15 dB.