Abstract: A method for treating a photorefractive effect of an optical device, which comprises irradiating an optical device comprising a lithium niobate single crystal or a lithium tantalate single crystal with an ultraviolet light having a wavelength of at least 300 nm and at most 400 nm so as to suppress and control a photo-induced refractive index change (photorefractive effect) caused on the device.

Abstract: A solid-state light source apparatus includes a first excitation laser light source for outputting a laser beam of a first wavelength, a second excitation laser light source for outputting a laser beam of a second wavelength, a difference frequency between the laser beam of the first wavelength and the laser beam of the second wavelength being in a terahertz band, and a semiconductor pseudo phase matching device which is disposed at a place where a first optical axis of the laser beam of the first wavelength overlaps with a second optical axis of the laser beam of the second wavelength, and generates a terahertz beam in a direction coaxial with the first and second optical axes on the basis of irradiation of the laser beams of the first and second wavelengths. Thus, high output and high efficiency terahertz wave generation can be easily and certainly realized while a narrow line width characteristic is maintained.

Abstract: A solid-state light source apparatus includes a first excitation laser light source for outputting a laser beam of a first wavelength, a second excitation laser light source for outputting a laser beam of a second wavelength, a difference frequency between the laser beam of the first wavelength and the laser beam of the second wavelength being in a terahertz band, and a semiconductor pseudo phase matching device which is disposed at a place where a first optical axis of the laser beam of the first wavelength overlaps with a second optical axis of the laser beam of the second wavelength, and generates a terahertz beam in a direction coaxial with the first and second optical axes on the basis of irradiation of the laser beams of the first and second wavelengths. Thus, high output and high efficiency terahertz wave generation can be easily and certainly realized while a narrow line width characteristic is maintained.

Abstract: A method for fabricating an SHG device by forming an inversion region having a first direction of polarization selectively in a ferroelectric substrate that has a second, opposite direction of polarization. A proton exchange process exchanges cations in the ferroelectric substrate with protons, selectively in correspondence to each portion of the substrate in which an inversion region is to be formed. Electrodes are provided on upper and lower major surfaces of the ferroelectric substrate, and the inversion region is selectively grown in a direction perpendicular to the upper major surface of the ferroelectric substrate while applying a d.c. voltage to the electrode on the upper major surface of the ferroelectric substrate thereby to induce an electric field acting in a direction coincident with the direction of said first polarization in said ferroelectric substrate.

Abstract: A waveguide type second-harmonic generation element includes a substrate made of LiTaO.sub.3, approximately parallel domain inversion regions formed on the substrate and extending in a first direction, where the domain inversion regions have a first depth into the substrate, approximately parallel domain non-inversion regions formed on the substrate and extending in the first direction, where the domain inversion region and the domain non-inversion regions alternately occur on the substrate, and an optical waveguide formed on the substrate and traversing the domain inversion regions and the domain non-inversion regions, where the optical waveguide has a second depth and extends in a second direction which is approximately perpendicular to the first direction.