Abstract: A first electrode and a second electrode are provided in separation on a main surface of a substrate made of a ferroelectric single crystal. A first voltage is applied to between the first electrode and the second electrode, for example on condition that the first electrode is positive and the second electrode is negative, to generate and grow a first polarization-inversed portion toward the second electrode from the first electrode. Then, the distance between the first electrode and the second electrode is changed, and a second voltage is applied to between the first electrode and the second electrode on the same condition, to generate and grow a second polarization-inversed portion, in a different area from that of the first polarization-inversed portion, toward the second electrode from the first electrode.

Abstract: An optical waveguide element is disclosed, which includes a three-dimensional optical waveguide of a bulky non-linear optical crystal, a substrate, and a joining layer made of an amorphous material through which the substrate is joined to the optical waveguide.

Abstract: A method of processing a substrate made of a ferroelectric single crystalline material, including the steps of forming a desired proton-exchanged layer in the substrate by proton-exchanging a portion of the substrate, and selectively removing the proton-exchanged layer to form a concave ditch structure in the ferroelectric single crystalline substrate, wherein the desired proton-exchange layer is formed by using an acid containing a lithium salt as a proton-exchanging source, the surface of the substrate from which the concave ditch structure is formed is an X-cut surface or a Z-cut surface, as a main surface, of the ferroelectric single crystalline material used as the substrate, and the concave ditch structure has a recessed portion with its depth equal to or larger than its half opening width.

Abstract: In producing an optical single crystal epitaxial film from a melt containing a transition metal on a single crystal substrate by a liquid phase epitaxial method, this process contains the steps of: annealing the film at a predetermined temperature in an ozonic atmosphere; and temperature-increasing and -decreasing to and from the predetermined temperature, wherein at least one of temperature-increasing and -decreasing steps, the film is exposed to a substantially ozone-free atmosphere.

Abstract: A process for producing an optical waveguide substrate including a ridge-shaped structural portion containing at least an optical waveguide, which process including the steps of forming an optical waveguide-forming layer on a substrate body to prepare a substrate workpiece, and forming said ridge-shaped structural portion at said substrate workpiece by grinding.

Abstract: A process for forming a microstructure at a surface of a substrate made of a ferroelectric single crystal, includes the steps of subjecting the substrate to a single-poling treatment, thereby one of an etching-easy surface and an etching-difficult surface being exposed to one of main faces of the substrate, while the other being exposed to the other main face, forming a domain-inverted region in at least one of the main faces of the substrate, and forming the microstructure at the substrate in the domain-inverted region of the substrate by selectively etching the substrate.

Abstract: A process is disclosed for producing an integrated composite oxide single crystal body composed of a core portion made of an oxide single crystal and a clad portion integrated with the core portion and made of another oxide single crystal having a composition different from that of the oxide single crystal constituting the core portion, the process comprising the steps of: (1) preparing a first melt in a first crucible by melting a first material for a first oxide single crystal to constitute the core portion inside the first crucible, (2) preparing a second melt inside a second crucible by melting a second material for a second oxide single crystal to constitute the clad portion inside the second crucible, (3) contacting a seed crystal to the first and second melts, (4) pulling down the first melt through a pull-out opening of the first crucible, (5) pulling down the second melt through a pull-out opening of the second crucible and contacting the pulled-down second melt with a pulled-down portion of the firs

Abstract: In producing an optical single crystal epitaxial film from a melt containing a transition metal on a single crystal substrate by a liquid phase epitaxial method, this process contains the steps of: annealing the film at a predetermined temperature in an ozonic atmosphere; and temperature-increasing and -decreasing to and from the predetermined temperature, wherein at least one of temperature-increasing and -decreasing steps, the film is exposed to a substantially ozone-free atmosphere.

Abstract: An optical waveguide substrate having a substrate made of ferroelectric optical single crystal and a ridge portion projected from a main plane of the substrate, has a construction such that the ridge portion has a base portion made of ferroelectric optical single crystal and an optical waveguide formed on the base portion. The optical waveguide substrate is formed by forming at least one optical waveguide layer on a main plane of a substrate made of ferroelectric optical single crystal, and mechanically working main planes of the optical waveguide layer and the substrate to form a ridge portion projected from the main plane of the substrate. The optical waveguide substrate can reduce a light transmission loss, increase an extinction ratio, and improve an electric field applying efficiency.

Abstract: Optoelectric article includes a substrate made of an optoelectric single crystal and a film of a single crystal of lithium niobate formed on the substrate by a liquid phase epitaxial process, wherein a ratio of lithium/niobium of a composition of the film of the lithium niobate single crystal falls in a range of 48.6/51.4 to 49.5 to 50.5 or 50.5/49.5 to 52.3/47.7.

Abstract: An excellent periodic domain-inverted structure formed on a ferroelectric optical single crystal substrate is provided having an improved crystalline property of the substrate and an improved resistance to optical damage and output of the domain-inverted structure and the like optical waveguide structure by forming protruded and recessed portions on a single-domained ferroelectric optical single crystal substrate 1, growing a film of a ferroelectric optical single crystal film 4 on the respective recessed portion of the single crystal substrate 1 by a liquid phase epitaxial growing process. At that time, the Curie temperature of the film 4 is lower than the liquid phase epitaxial growing temperature of the film 4, and the Curie temperature of the substrate 1 is higher than the liquid phase epitaxial growing temperature of the film 4, and the film 4 is polarized in an opposite direction to the polarization direction of the substrate 1.

Abstract: A process for producing an optical waveguide device including a substrate and a ridge-shaped optical waveguide projected at a main plane of the substrate, comprising the steps of: forming said ridge shaped optical waveguide at the main plane of the substrate by abrasion working.

Abstract: An optical single crystalline article comprising a substrate made of an optical single crystal and an epitaxial film formed on said substrate and made of an optical material, wherein a crystalline structure of said epitaxial film is a relaxed structure.

Abstract: A second harmonic generation element including a single crystal substrate having a fundamental composition of K.sub.3 Li.sub.2-2x (Nb.sub.1-y Ta.sub.y).sub.5+5z O.sub.15-x+12.5z and an optical waveguide made of an epitaxial film with a fundamental composition of K.sub.3 Li.sub.2-2a (Nb.sub.1-b Ta.sub.b).sub.5+5c O.sub.15-a+12.5c and refractive index different from that of the single crystal substrate, wherein:-0.5.ltoreq.a, x.ltoreq.0.6250.ltoreq.b, y.ltoreq.0.50.8.ltoreq.(5-2x)/(5+5z), (5-2a)/(5+5c).ltoreq.1.2.

Abstract: A film made of lithium niobate-lithium tantalate solid solution may be formed on a single crystal substrate having a composition of LiNb.sub.1-z Ta.sub.z O.sub.3 (0.ltoreq.z<0.8) by the liquid phase epitaxial process. The substrate is contacted with supercooled liquid phase of a melt to produce the film thereon. The melt consists mainly of Li.sub.2 O.sub.3, Nb.sub.2 O.sub.5, Ta.sub.2 O.sub.5 and a flux. A composition of the liquid phase is within a region encompassed by a straight line K linking a point A (95, 5, 0) and a point B (95, 2, 3), a straight line G linking the point A (95, 5, 0) and a point C (60, 40, 0), a straight line H linking the point C (60, 40, 0) and a point D (60, 0, 40), a straight line J linking the point B (95, 2, 3) and a point E (0, 40, 60) and a curved line I defining a composition whose saturation temperature is not more than 1200.degree. C. Each line is shown in a triangular diagram of a pseudo-ternary system of LiNbO.sub.3 -LiTaO.sub.3 --a melting medium.

Abstract: Optoelectric article includes a substrate made of an optoelectric single crystal and a film of a single crystal of lithium niobate formed on the substrate by a liquid phase epitaxial process, wherein a ratio of lithium/niobium of a composition of the film of the lithium niobate single crystal falls in a range of 48.6/51.4 to 49.5 to 50.5 or 50.5/49.5 to 52.3/47.7.

Abstract: A process is disclosed for producing a film of an oxide type single crystal on a substrate of such an oxide type single crystal by epitaxially growing the oxide type single crystal on the substrate through contacting the substrate onto a melt in an overcooled state. The substrate of the oxide type single crystal is contacted with the melt held in a first furnace, and the substrate of the oxide type single crystal is held inside a second furnace separated from said first furnace, and the temperature of the substrate is adjusted in the second furnace. An oxide type single crystal film-producing apparatus is also disclosed.

Abstract: According to the invention, a film of optoelectric single crystal may be formed on a substrate made of optoelectric single crystal by a liquid phase epitaxial process. The process comprises the steps of producing a melt of a solute and a melting medium, a solid phase and a liquid phase coexisting in the melt; then cooling the liquid phase for producing super cooling state in the liquid phase; and contacting the substrate to the liquid phase to form the film on the substrate by an epitaxial growing process. The film may be produced on the substrate, the film having a half value width of an X-ray rocking curve not more than that of the substrate.

Abstract: A process for producing optoelectric articles, in which an optoelectric single crystal film is formed on an optoelectric single crystal substrate, is disclosed. The optoelectric single crystal substrate is exposed to a liquid phase in a supercooling state of a melt including a solute and a melting medium, and the optoelectric single crystal film is formed by a liquid phase epitaxial process. In this case, a viscosity of the liquid phase is set to 75%.about.95% preferably 75%.about.90% with respect to a viscosity at which a degree of supercooling of the liquid phase is zero.