Fig. 1. Schematic diagram of high-sensitivity refractive index sensor based on SSlot waveguide. (a) Three-dimensional view; (b) top view and related structure parameters

Fig. 2. Schematic diagram of coupling grating. (a) Three-dimensional structure; (b) top view and related structure parameters

Fig. 3. Schematic diagram of chip preparation process

Fig. 4. Schematic diagrams and mode field diagrams of strip waveguide, Slot waveguide, and SSlot waveguide. (a)(b) Strip waveguides; (c)(d) Slot waveguides; (e)(f) SSlot waveguides

Fig. 5. S_W varies with widths of waveguides in strip waveguide, Slot waveguide, and SSlot waveguide

Fig. 6. S_W varies with g and d in SSlot waveguide. (a) g; (b) d

Fig. 7. Diagrams of mode converter and mode field distribution, and conversion efficiency varying with length and width of tapered waveguide. (a) Structure and model field diagrams; (b) conversion efficiency

Fig. 8. Phase difference ϕ between strip waveguide and mode converter

Fig. 9. Phase difference Δφ between upper and lower arms of refractive index sensor and output power varying with wavelength

Fig. 10. Transmission spectra of sensor under different refractive index

Fig. 11. Relationship between wavelength offset and refractive index change