Fig. 1. （a）Cross-section schematic of the LNOI thin film waveguide，（b）& （c）the normalized distribution of optical fields at the fundamental frequency and the second harmonic frequency，respectively

Fig. 2. （a）The poling period of different types of phase matching，（b）the vibration of the third-order poling period of e+e→ematching and the first-order poling period of o+o→ematching with the height of waveguide，（c）the relationship between the width and height of LNOI thin film and the poling period.

Fig. 3. The n_eff of LNOI waveguide modes changed with temperature at 1550 nm wavelength，（a）TE₀，（b）TM₀

Fig. 4. Simulation results of different types of phase matching，（a）& （b）the relationship between the poling period and wavelength at different temperatures，（c）& （d）the temperature changed with the matched wavelength under the specific poling period

Fig. 5. The normalized conversing efficiency at different temperatures，（a）e+e→ematching，（b）o+o→e matching