Abstract: A core section (10a) is formed in an optical fiber (10) made of a glass material and, electrodes (14a and 14b) are inserted into the clad section (10b) of the fiber (10). When the core section (10a) is irradiated with ultraviolet rays in prescribed intensity patterns while a high voltage is applied to the electrodes (14a and 14b), a grating section (16) in which non linear areas (16a) and normal areas (16b) are alternately formed is formed in the section (10a). The characteristics of the grating section (16) can be changed by utilizing an electrooptic effect by impressing a prescribed electric field upon the section (16) through the electrodes (14a and 14b). A grating element constituted in such a way can be utilized as an optical functional element, such as the wavelength switch, because the Bragg wavelength of the element changes when a voltage is applied.

Abstract: A method of inducing or enhancing the electro-optic properties of an optically transmissive material such as an optical fiber (1) which comprises applying an electric field by means of electrodes (4) to the optical fiber and subjecting the material to UV radiation (9).

Abstract: The optical waveguide device comprises an optical waveguide formed as a region having a high index of refraction on a surface or in an interior including the surface of a base plate made of a ferroelectric crystal, and a film covering the surface of said optical waveguide in the direction along the c axis of said crystal phase plate and having electrical conductance higher than that of the optical waveguide. The optical waveguide is formed by thermal diffusion or a chemical reaction. This optical waveguide device is affected little by the optical damage and can be manufactured easily.

Abstract: An optical waveguide produced from a lithium niobate single crystal substrate diffused thereon titanium is claimed, wherein, as the substrate is used a single crystal of lithium niobate having an optical absorbance coefficient of 0.03 cm.sup.-1 or less for a light 420 nm in wavelength. The optical waveguide according to the present invention shows improved resistance against optical damage as compared with prior art waveguides, and is therefore suitable for devices subjected to incidence beam of higher intensity.