Fig. 1. OAM structure diagram and its trench section

Fig. 2. Concept and principle of OAM generator

Fig. 3. Mode conversion in waveguides

Fig. 4. Conversion efficiency versus different height and width of S waveguide

Fig. 5. Effective index of modes in waveguide versus height of waveguide

Fig. 6. Conversion efficiency of wg1 versus coupling length between different waveguide distances

Fig. 7. Overlap of orthogonal eigenmode at 1 550 nm versus size of trench

Fig. 8. Conversion efficiency of OAM versus trench length

Fig. 9. Detected light field at other ports with TE₀₀ input in Port1, Port2 and Port3, respectively

Fig. 10. Light field of TE₀₀ incident from different ports detected at Port 4 and phase diagrams of OAM_±1

Fig. 11. Conversion efficiency of OAM with wavelength of 1.45~1.65 μm