Optical wavelength conversion devices

Claim 1

An optical wavelength conversion device comprising: an optical waveguide (2) formed on a substrate (1) of a non-linear optical material so as to generate a secondary harmonic wave by Cerenkov radiation, the waveguide (2) comprising a first waveguide passage (2a, 2c) for confining a fundamental wave and converting it into a secondary harmonic wave, and a second waveguide passage (2b) for confining said secondary harmonic wave and propagating it towards an end face for emission therefrom, characterised in that: said waveguide (2) is formed in a ridge shape on said substrate (1), and said first waveguide passage (2a, 2c) is formed so as to be in contact with said second waveguide passage (2b) along at least one of the lateral sides of the ridge; and in that n₂ > n₃ > n₁, where n₁, n₂ and n₃ are, respectively, the refractive indices of said substrate (1), said first waveguide passage (2a, 2c) and said second waveguide passage (2b); and in that said first and second waveguide passages (2a, 2c, 2b) are formed so as to satisfy: W r f < a < W r s, W r f or W r s < b, and W r s < c where a is the width of said first waveguide passage (2a, 2c) in a direction which is parallel to said substrate (1), b is the depth of said first waveguide passage (2a, 2c) in a direction which is perpendicular to the face of said substrate (1), c is the depth of said second waveguide passage (2b) in a direction which is perpendicular to the face of said substrate (1), W r f is the fundamental wave cut-off thickness below which propagation of the fundamental wave is prevented, and W r s is the secondary harmonic wave cut-off thickness below which propagation of the secondary harmonic wave is prevented.