Compact low-birefringence polarization beam splitter using vertical-dual-slot waveguides in silicon carbide integrated platforms

The polarization beam splitter is a key component for polarization manipulation in photonic integrated circuits, but it is challenging to design for low-refractive-index optical materials, due to the low birefringence of the waveguides. We propose what we believe is a novel compact vertical-dual-slot waveguide-based coupling scheme for silicon carbide, enabling efficient low-birefringence polarization splitting by extensively modulating the transverse-magnetic mode distribution. We numerically and experimentally demonstrate the device in the 4H-silicon-carbide-on-insulator integrated platform, with a small footprint of 2.2 μm×15 μm2.2 μm×15 μm. The device, easy to fabricate via a single lithography process as other components on the chip, exhibits low insertion loss of <0.71 dB<0.71 dB and <0.51 dB<0.51 dB for the transverse-electric and transverse-magnetic polarized light, respectively, and polarization extinction ratio of >13 dB>13 dB, over 80 nm wavelength range.