Fig. 1. (a) Refractive index increment as a function of surface proton concentration C0 in 6 μm wide channel APE waveguides with annealing depth of 3 μm. (b) Theoretical poling period for our APE PPLN structure as a function of temperature, where the surface proton concentration C0 varies from 0.12 to 0.16.

Fig. 2. (a) SEM picture of SiO2 mask. (b) Image of the inverted domain structure of the APE waveguide recorded using confocal SH microscopy. (c) The measured and fitted transmission spectra of the waveguide.

Fig. 3. Schematic experimental setup. The two insets are the images of the FW and SH wave, respectively.

Fig. 4. Temperature tuning curve of APE PPLN waveguide with 11.78 μm poling period. The black dots and the dashed red line are the measured data and fitted curve, respectively.

Fig. 5. Measured SHG conversion efficiency as a function of the power of FW with (a) CW and (b) 50 ns, 10 kHz pulsed input. The blue dots and the green line correspond to the measured conversion efficiency and the linear fitting curve, respectively.