1：Experimental Design and Method Selection:

Femtosecond laser direct writing was used to fabricate dual-line and rectangular depressed-cladding waveguides in 6H–SiC crystals. The method leverages the ultrashort pulse width and high peak intensity of femtosecond lasers for precise modifications.

2：Sample Selection and Data Sources:

Semi-insulating 6H–SiC crystals oriented along the (0001) direction were used. The crystals were cut and polished to prepare for waveguide fabrication.

3：List of Experimental Equipment and Materials:

A femtosecond fiber-laser system (FemtoYLTM-25, YSL Photonics), microscope objective (Sigma, 50×, N.A. = 0.67), metalloscope (Axio Imager, Carl Zeiss), NIR CMOS camera (CinCam CMOS 1201, Cinogy Technologies), and confocal microscope (NanoBase XperRam200) were used.

4：67), metalloscope (Axio Imager, Carl Zeiss), NIR CMOS camera (CinCam CMOS 1201, Cinogy Technologies), and confocal microscope (NanoBase XperRam200) were used. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: The femtosecond laser was focused into the 6H–SiC crystals to create waveguides. The sample was placed on a precision translation stage for controlled movement. Mode profiles and propagation losses were measured using an end-face coupling system.

5：Data Analysis Methods:

Confocal micro-Raman spectroscopy was used to analyze the laser-induced modifications. The refractive index changes were estimated by measuring the N.A. of the waveguides.