Fig. 1. (Color online) The structure of the EO modulator made by Wang et al.^[6].

Fig. 2. (Color online) (a) Optical image of the modulators on the chip fabricated in our group. (b) SEM image of the electrode of the modulator. (c) SEM image of the cross section of the modulator’s waveguide. (d) SEM image of the area where the electrode stepping over the waveguide.

Fig. 3. (Color online) (a) The transmission spectrum of the modulator with and without the voltage applied. (b) The measured EO response of the modulator.

Fig. 4. (Color online) (a) Monolithic integrated photonic circuit for frequency comb generation and manipulation^[13]. (b) Integrated EO comb generator^[22]. (c) LN microring mode-locked Kerr solitons. (d) Photorefractive and optical Kerr effect^[7].

Fig. 5. (Color online) SEM images of the microring resonator. (a) Coupling region of micro-ring. (b) Cross-section of waveguide. (c) Lorentz fitting of the resonance peak at 1572.6 nm, the Q-factor is 1.78 million^[23].

Fig. 6. (Color online) Optical spectrum of a frequency comb pumped at 1549.927 nm.

Fig. 7. (Color online) (a) SEM of the one-dimensional optomechanical crystal (OMC) design^[33]. (b) Schematic layouts of MZI- and resonator-type AOMs^[34]. (c) Microscope image of a suspended acousto-optic MZI and a suspended optical racetrack cavity with a thin-film acoustic resonator and these acoustic S₁₁ and opto-acoustic S₂₁ spectra^[35].

Fig. 8. (Color online) (a) Schematic of poling electrodes and silicon nitride (SiN) strip on 700 nm thick x-cut MgO:LN thin film. (b) Zoomed-in view of poling electrode tip showing 160 nm chromium (Cr) on top of 100 nm SiO₂. (c) Poling circuit; pulses generated from an arbitrary waveform generator (AWG) are amplified by a high voltage amplifier (HVA) and applied to a sample covered with silicone oil^[37].

Fig. 9. Top-view SEM of a poled MgO-LN mesa after etching in hydrofluoric acid.

Fig. 10. (Color online) Zoomed-in view of the SHG spectral response of the 1440-nm-wide device (solid curve), together with the theoretically predicted responses^[38].

Fig. 11. (Color online) SHG total conversion efficiency as a function of input power in the pump-depletion region. The inset shows the input-output power relation in the low-conversion limit^[38].

Fig. 12. (Color online) (a) Numerical simulation of the poling period for QPM between the pump TE 00 and SH TM 00 modes using the Sellmeier equation for congruent LN. (b) Applied poling pulse shape. (c, d) False-color SEM images of a PPLN microring resonator etched with hydrofluoric acid and its zoomed-in view, revealing a poling duty cycle of ~35%^[41].

Fig. 13. (Color online) (a) P_SHG–P_p² relation. A linear fit is applied to the experimental data in the low-power region. A fitted slope of 1.02 implies a quadratic dependence of SHG power on the pump power. An SHG conversion efficiency of 250 000%/W is extracted. (b) Absolute conversion efficiency as a function of pump power, including the experimental data and theoretical fit^[41].

Fig. 14. (Color online) (a) Structure of the edge coupler. (b) Overhead view of the edge coupler^[48].

Fig. 15. (Color online) (a) Transmission spectrum of the fabricated single coupler. (b) Coupling loss versus different tip widths of the lower LN inversed taper (TE mode)^[48].