Fig. 1. (a)~(c) LNOI structure: (a) diffused waveguide; (b) loaded waveguide; (c) ridge waveguide. (d) SOI structure

Fig. 2. Schematic diagrams of (a) MZI structure and (b) MI structure

Fig. 3. Light intensity distribution diagram of the output port of the resonant cavity structure waveguide^[16]. (a) Microring structure; (b) photonic crystal structure. The blue line is the optical characteristic change curve of the waveguide after an electric field is applied

Fig. 4. (a) Tapered coupling model^[19]; (b) inverse tapered coupling model^[19]; (c) grating coupling model^[19]; (d) evanescent coupling model^[19]

Fig. 5. Optical fiber and modulator integration scheme^[29]. (a) Modulator structure; (b) waveguide structure when light propagates in an optical fiber; (c) waveguide structure when light propagates in a waveguide

Fig. 6. Electrode basic structure of LN modulators. (a) The electric field direction is parallel to the waveguide core; (b) the electric field direction is perpendicular to the waveguide core

Fig. 7. (a) Lumped electrode structure; (b) traveling wave electrode structure

Fig. 8. (a)~(d) CMP process flow chart and (e) CMP system structure diagram^[58]

Fig. 9. Waveguide image (a) before and (b) after FIBm^[59]

Fig. 10. Diamond cutting process for manufacturing waveguides^[61]

Fig. 11. The light field change diagram of the output port of the modulator. (a) PM; (b) MZM; (c) MIM; (d) MRM; (e) PHCM