Fig. 1. Single-mode transmission conditions of Si₃N₄ waveguide. (a) TE mode; (b) TM mode

Fig. 2. Effective refractive index of Si₃N₄ waveguide under TE and TM modes. (a) Core layer width is 4 μm; (b) core layer width is 5 μm

Fig. 3. Mode field distributions of Si₃N₄ waveguide under different core layer thicknesses. (a)(d) 40 nm; (b)(e) 100 nm; (c)(f) 200 nm

Fig. 4. Cross-sectional structure of Si₃N₄ waveguide

Fig. 5. Mode losses of Si₃N₄ waveguides under different bending radii. (a) TE mode; (b) TM mode

Fig. 6. Crosstalk conditions of waveguides under different spacings

Fig. 7. Structural diagram of proposed tapered vertical coupler

Fig. 8. Crosstalk conditions of waveguide claddings under different spacings

Fig. 9. Transmittance values and coupling efficiencies between Si₃N₄ waveguides under different tapered waveguide end face sizes.

Fig. 10. Schematics of Si₃N₄ interlayer coupling interference ring. (a) Light field transmission; (b) interlayer coupling interference ring

Fig. 11. Process flow of Si₃N₄ interlayer coupling interference ring