Fig. 1. Three-dimensional structure diagram of mode splitter

Fig. 2. Initial structure of mode splitter and optimized structure of mode splitter. (a) Initial structure of mode splitter; (b) optimized structure of mode splitter

Fig. 3. Flowchart diagram of inverse design

Fig. 4. Process diagram of inverse design. (a) FOM varying with iteration number; (b) perturbation of gradient field; (c) permittivity distribution; (d) forward direction field distribution within device

Fig. 5. H_y fields of TE₁ mode and TE₀ mode input in port I at wavelength of 1550 nm. (a) TE₁ mode; (b) TE₀ mode

Fig. 6. Optimized transmittance spectra. (a) Inputting TE₁ mode; (b) inputting TE₀ mode

Fig. 7. Transmittance spectra for different design error. (a) Inputting TE₁ mode; (b) inputting TE₀ mode

Fig. 8. Transmittance spectra for error of -15 nm. (a) Inputting TE₁ mode; (b) inputting TE₀ mode

Fig. 9. Transmittance spectra for error of 15 nm. (a) Inputting TE₁ mode; (b) inputting TE₀ mode