Fig. 1. Cross-sectional view of the traditional electrode

Fig. 2. Cross-sectional view of the sinking-electrode

Fig. 3. Variation of the loss variation and the half-wave voltage of the modulator with the gap between the electrodes at different electrode heights

Fig. 4. Electric field distribution of the sinking-electrode design and the traditional electrode design at different electrode heights

Fig. 5. Variation of the phase Δφ_m with the electrode height

Fig. 6. Optical field distribution of the fundamental mode on the modulator transmission cross-section

Fig. 7. The side-wall inclination angle α_e introduced by manufacturing errors on the cross-section of the modulator,and the deviation ΔP_e of the center position of the electro-optic field

Fig. 8. The variation curve of phase difference Δφ_m with electrode position and inclination deviation. (a) Deviation of the center position of the electro-optic field (± 5 V modulation); (b) side-wall angle

Fig. 9. Etching results of the sinking-electrode tank. (a) Picture of the experimental sample; (b) the upper surface of the etched tank; (c) 3D scanning micrograph of the etched tank; (d) section profile of the etched tank