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

Area of Science:

• Photonics and Materials Science
• Integrated Optics
• Semiconductor Devices

Background:

• Silicon carbide (SiC) is a promising material for photonic integrated circuits due to its unique optical and electronic properties.
• Efficient light confinement and low loss are critical for on-chip SiC photonic applications.

Purpose of the Study:

• To investigate and optimize the optical characteristics of large cross-section SiC rib waveguides for single-mode operation.
• To minimize mode field mismatch and coupling loss between SiC waveguides and standard single-mode fibers.
• To develop a fabrication process for high-quality SiC-on-insulator (SiCOI) waveguides.

Main Methods:

• Finite difference method was used to analyze and control waveguide geometric parameters for mode field distribution.
• Thinning and polishing techniques were employed for SiCOI fabrication.
• Micro-nano fabrication, including lift-off and inductively coupled plasma etching, was developed for precise SiC waveguide definition.
• Facet cutting and directional polishing were used for end-face quality improvement.

Main Results:

• Achieved high-quality SiCOI with <10 µm SiC thickness and ~0.34 nm RMS surface roughness.
• Developed a precise SiC etching process with ~785 nm/min etch rate and >88.6° sidewall verticality.
• Demonstrated low mode field mismatch loss (<0.3 dB/facet) at 1550 nm with standard single-mode fiber.
• Achieved low transmission loss (~0.6 dB/cm) in fabricated SiC waveguide devices.

Conclusions:

• The study successfully optimized SiC rib waveguides for efficient light propagation and coupling.
• The developed fabrication process enables high-quality SiC photonic devices meeting on-chip research demands.
• These findings pave the way for advanced SiC-based integrated photonic circuits with minimal optical losses.