Secondary harmonic generator having waveguides for a laser beam

Claim 1

An optical wavelength conversion device, comprising: an optical waveguide formed on a substrate of a nonlinear optical material so as to generate a secondary harmonic wave by Cerenkov radiation, and having a first waveguide passage for confining a fundamental wave and converting it into a secondary harmonic wave, and a second waveguide passage for confining said secondary harmonic wave and propagating it toward an end face for emission therefrom, wherein said first and second waveguide formed with a ridge shape on a substrate, and said first waveguide passage is formed so as to be in contact with said second waveguide passage on at least one of the lateral side surfaces of said ridge which is perpendicular to the major surface of said substrate, wherein the following condition is satisfied, n.sub.2 >n.sub.3 >n.sub.1 wherein n 1 , n 2 and n 3 are, respectively, the refractive indices of said substrate, said first waveguide passage and said second waveguide passages, and wherein said first and second waveguide passages are formed so as to satisfy the conditions W.sub.r f<a<W.sub.r s, W.sub.r f or W.sub.r s<b, and W.sub.r s<c wherein a is the width of said first waveguide passage in a direction which is parallel with said major surface of said substrate, b is the depth of said first waveguide passage in a direction which is perpendicular to the major surface of said substrate, c is the depth of said second waveguide passage in a direction which is perpendicular to the major surface of said substrate, W r F is the cutoff thickness for the fundamental optical wave, and W r s is the cutoff thickness for the secondary harmonic wave.