Patent ID: 7985294

Claim:
A method of manufacturing an optical device comprising the steps of: forming a dopant layer on a stoichiometric lithium niobate single crystal substrate with Li to Nb mole composition ratio of 49.5% to 50.5%; and diffusing a dopant in the dopant layer into at least a portion of the stoichiometric lithium niobate single crystal substrate, wherein the stoichiometric lithium niobate single crystal substrate comprises 0.5 to 5 mol % of Mg: and wherein, in the diffusing step, a heat treatment is performed at a diffusion temperature of 1000° C. to 1200° C. for a diffusion time of 3 hours to 24 hours in a dry atmosphere of at least one of O 2 , N 2 , Ar and He gas having a dew-point temperature of −35° C. or less.