Ultra-compact and fabrication-tolerant polarization rotator based on a bend asymmetric-slab waveguide

We propose and analyze a polarization rotator based on a bend asymmetric-slab waveguide on the silicon-on-insulator platform. The device can be fabricated using standard complementary metal–oxide–semiconductor process involving only two dry etching steps. Compared with the formerly reported polarization rotators based on two-step etching, our introduced device demonstrates a significant improvement for fabrication tolerance. Furthermore, an ultra compact structure of ∼5  μm conversion length, an insertion loss of only 0.5 dB, and an extinction ratio of >40  dB for both TE to TM polarization conversion and TM to TE polarization conversion are exhibited. Operation wavelength and the influence of environmental temperature on our device are also discussed.