Large cross-section rib waveguides based on 4H-silicon carbide on insulator

We explored the optical characteristics of large cross-section rib silicon carbide (SiC) waveguides under single-mode operation. Utilizing the finite difference method, we systematically adjusted the geometric parameters to effectively control the spatial distribution of the mode field. We investigated the mode field mismatch between SiC rib waveguides and single-mode fiber, providing a theoretical basis for optimizing waveguide parameters to minimize coupling loss. Employing thinning and polishing techniques, we achieved high-quality SiC on insulator fabrication with a top SiC layer thickness of less than 10 µm and a surface roughness RMS of ∼0.34nm, meeting the demands of on-chip SiC photonics research. A micro-nano fabrication process was developed, including the lift-off technique for high-quality metal mask patterning and inductively coupled plasma etching for precise SiC deep etching, achieving an etch rate of ∼785nm/min with sidewall verticality over 88.6° and depths exceeding 10 µm. Post-processing, including facet cutting and directional polishing, led to SiC waveguide devices with excellent end-face quality. Testing on a custom horizontal coupling platform demonstrated that at 1550 nm, the mode field mismatch loss with standard SMF was less than 0.3 dB/facet, and the transmission loss was∼0.6dB/cm.