Proton-exchanged waveguides for sum-frequency generation

Claim 1

An optical device for use in producing sum-frequency waves, including second harmonic waves, when laser light from at least one laser source is coupled thereinto, said optical device comprising: a substrate made of a ferroelectric material; and a channel waveguide formed in said substrate by either proton-exchange or in-diffusion of ions capable of raising the index of refraction of said substrate material in at least one azimuth, said channel waveguide having a width, depth, and effective index of refraction for propagating radiation of preselected wavelengths along the length of said channel waveguide in no more than two modes to maximize the power density of propagating radiation to generate sum-frequency, including second harmonic, Cerenkov radiation waves due to nonlinear interactions of propagating radiation, said sum-frequency radiation comprising one portion which radiates directly into said substrate and another portion that is directed into said substrate by total internal reflection at the top surface of said waveguide, a ratio of said preselected wavelengths to said depth of said channel waveguide being within the range between 0.4 and 0.55 so that said sum-frequency portions constructively interfer in phase with one another in said substrate so that said sum-frequency radiation is maximized.

Claim 12

A method for fabricating an optical device for use in producing sum-frequency waves in response to pumping with laser radiation of predetermined wavelengths where the device comprises a ferroelectric waveguide disposed on a substrate, said method comprising the steps of: fabricating on a ferroelectric substrate by ion diffusion or proton exchange several waveguides that will support at most two modes of radiation that propagate along the waveguides at preselected wavelengths, said waveguides having the same width and effective index of refraction but different depth, a ratio of said preselected wavelengths to said depth of said channel waveguide being within the range between 0.4 and 0.55, coupling laser radiation of the predetermined wavelengths into the waveguides to produce Cerenkov sum-frequency waves; measuring the intensity of the radiation coupled into the waveguides and the intensity of the sum-frequency waves produced; determining the waveguide depth for which a peak value of the intensity of the produced sum-frequency waves occurs as a function of waveguide depth; and fabricating at least one more waveguide in the material of the substrate at the depth having the peak response.

Claim 13

A method for fabricating an optical device for use in producing sum-frequency waves in response to pumping with laser radiation of predetermined wavelengths where the device comprises a ferroelectric waveguide disposed on a substrate, said method comprising the steps of: fabricating on a ferroelectric substrate by ion diffusion or proton exchange several waveguides that will support at most two modes of radiation that propagate along the waveguides at preselected wavelengths, said waveguides having the same width and effective index of refraction but different depth, a ratio of said preselected wavelengths to said depth of said channel waveguide being within the range between 0.4 and 0.55, coupling laser radiation of the predetermined wavelengths into the waveguides to produce Cerenkov sum-frequency waves; measuring the intensity of the radiation coupled into the waveguides and the intensity of the sum-frequency waves produced; determining the waveguide depth for which a peak value of the intensity of the produced sum-frequency waves occurs as a function of waveguide depth; and fabricating at least one more waveguide in the material of the substrate at the depth having the peak response.