The most commonly used preparation methods for lithium niobate optical waveguides are proton exchange method and metal diffusion method. Due to the small difference in refractive index between the waveguide and substrate layer prepared by these two methods, their light confinement effect is weak, and the introduction of foreign ions during the production process can damage the properties of the lithium niobate crystal itself, thereby affecting the performance of the waveguide.

The ridge waveguide structure based on lithium niobate single crystal thin film (LNOI) greatly increases the difference in core shell refractive index of the waveguide, thereby enhancing the optical confinement effect of the waveguide and improving the nonlinear effects in lithium niobate waveguides. In addition, the optical damage threshold of lithium niobate ridge waveguides is higher, making them suitable for producing high-power frequency converter devices.