Method for manufacturing a polarization inversion layer of lithium naobate crystal

摘要

The present invention relates to a method of obtaining a polarization inversion by diffusing a titanium thin film on a + Z plane lithium naobate substrate, without forming a surface polarization inversion layer, and controlling the depth of polarization inversion by controlling the concentration of titanium diffused in the lateral direction. The present invention relates to a method for producing a polarization inversion layer having almost no surface waveguide after forming an optical waveguide at least in the amount of external diffusion of lithium oxide from a substrate.;In the method of forming a polarization inversion layer according to the present invention, a titanium thin film is formed on a portion where a polarization inversion layer is not to be formed on a + Z plane lithium naobate substrate, followed by heat treatment to diffuse titanium in a transverse direction to form a polarization inversion layer. It is.;According to the present invention, it is possible to control the polarization inversion depth without forming the surface polarization inversion layer by controlling the lateral diffusion of the titanium concentration, and thus the conversion efficiency of the quasi-phase matched integrated optical optical waveguide-type second harmonic generating element. Maximization can be realized very easily.