Fig. 1. Surface roughness diagram before and after annealing of As₂S₃ film

Fig. 2. Preparating process of As₂S₃ ridge waveguide

Fig. 3. Surface of As₂S₃ film developed with and without bottom film

Fig. 4. Photoprotective layer parameters

Fig. 5. Waveguide profile under different parameters

Fig. 6. As₂S₃ ridge waveguide topography diagram

Fig. 7. TE mode field distribution under the structural parameters of As₂S₃ ridge waveguide which was prepared

Fig. 8. Insertion loss of different lengths（at 1 550 nm guide mode）