Fig. 1. Effective refractive indexes of TE₀ and TE₁ modes versus W and wavelength. (a) Effective refractive index versus W when wavelength is 1500 nm; (b) effective refractive index versus W when wavelength is 1550 nm; (c) effective refractive index versus W when wavelength is 1600 nm; (d) effective refractive index versus wavelength

Fig. 2. Flow chart of designing mode converter based on edge optimization principle of adjoint method. (a) Initial structure of TE₀-TE₁ converter; (b) process of inverse design for TE₀-TE₁ converter by adjoint method; (c) optimized structure of TE₀-TE₁ converter; (d) FOM evolution curve of TE₀-TE₁ converter

Fig. 3. Performance analysis for TE₀-TE₁ converter in bandwidth range of 1500-1600 nm. (a) Electric field distribution of TE₀-TE₁ converter at 1550 nm; (b) output mode field of TE₀-TE₁ converter; (c) conversion efficiency; (d) extinction ratio; (e) insertion loss

Fig. 4. Conversion efficiency, extinction ratio, and insertion loss versus ΔW of TE₀-TE₁ converter at 1550 nm. (a) Conversion efficiency; (b) extinction ratio; (c) insertion loss

Fig. 5. SEM images of TE₀-TE₁ converter. (a) Structure of mode converter; (b) structure of mode speckle separation; (c) parallel test structure; (d) SEM image of test system of TE₀-TE₁ converter; (e) SEM image of TE₀-TE₁ converter

Fig. 6. Transmission, conversion efficiency, and insertion loss curves of TE₀-TE₁ converter. (a) Transmissivity; (b) conversion efficiency and insertion loss