Abstract: An optical waveguide element includes a substrate made of a lithium tantalate single crystal or a lithium niobate-lithium tantalate solid solution single crystal and a bulky optical waveguide made of a lithium niobate single crystal is directly joined to the substrate. The c-axis of the single crystal substrate is tilted at an angle with respect to the surface of the substrate to which the bulky optical waveguide is joined. The tilted angle is preferably within a range of 17-37 degrees.

Abstract: An optical waveguide element has a substrate made of a lithium tantalate single crystal or a lithium niobate-lithium tantalate solid solution single crystal and a bulky optical waveguide made of a lithium niobate single crystal directly joined the substrate. The c-axis of the single crystal to constitute the substrate is tilted from the surface of the substrate to be joined preferably by 17-37 degrees.

Abstract: An optical transmission member-fixed assembly including a substrate with a receipt groove in which a core wire of an optical transmission member is received, a lid integrated with the substrate, while between the substrate and the lid is provided a receipt space in which at least a covering of the optical transmission member is received, a dimension of the receipt space being greater than that of the receipt groove when viewed in a width direction, wherein an adhesive is filled around the core wire inside the receipt groove for fixing the core wire there, an adhesive is filled around the optical transmission member within the receipt space for fixing the optical transmission member there, a thickness of the adhesive filled around the optical transmission member inside a boundary space zone between the receipt space and the receipt groove is continuously reduced as a location of the boundary space zone is at least near and goes to an opening of the receipt groove at an end opposed to the receipt space.

Abstract: A compound optical waveguide device which is of a reduced size has an optical waveguide chip, a photodiode, and a laser diode. The optical waveguide chip has a substrate of LiNbO.sub.3, a Y-shaped optical waveguide, a phase modulator, and a polarizer. The substrate has an end face inclined at 70.degree. with respect to the optical axis of the Y-shaped optical waveguide. A photodiode is fixedly mounted on the substrate. A portion of light propagated through the Y-shaped optical waveguide is reflected by the inclined end face to enter the photodiode. Light emitted from the laser diode enters the Y-shaped optical waveguide through the inclined end face.

Abstract: A V groove and guide grooves are defined in a ceramic substrate, and an optical fiber is fixedly disposed in the V groove by the ceramic substrate and a cover, thereby producing a first optical waveguide chip. A V groove and guide grooves are also defined in another ceramic substrate, and an optical fiber is fixedly disposed in the V groove by the ceramic substrate and a cover, thereby producing a second optical waveguide chip. The first optical waveguide chip has an end face inclined to the direction of propagation of light through the optical fiber thereof, and the second optical waveguide chip also has an end face inclined to the direction of propagation of light through the optical fiber thereof. The first and second optical waveguide chips are positioned relatively to each other by guide pins intimately placed in the guide grooves, and the inclined end faces extend substantially parallel to each other with an air layer interposed therebetween.

Abstract: A first optical waveguide chip has a ceramic substrate and a cover, and the ceramic substrate has a V groove and guide grooves with an optical fiber being fixed in the V groove. A second optical waveguide chip has a ceramic substrate and a cover, and the ceramic substrate has a V groove and guide grooves with an optical fiber being fixed in the V groove. The first and second optical waveguide chips have respective end faces inclined 62.degree. to the direction in which light is propagated through the optical fibers. The first and second optical waveguide chips are positioned by guide pins intimately fitted in the guide grooves.

Abstract: A method for optically measuring an AC electric field or an AC voltage is disclosed. According to the method, a light beam emitted from a light-emitting portion is transmitted through a sensing head including a Pockel's-effect element while an AC electric field to be measured is applied to the Pockel's-effect element, so that the light beam is modulated by the applied AC electric field. The transmitted light beam is then received by a light-detecting portion, while in turn produces an electric signal corresponding to the received light beam. From the electric signal are selected a first component (E.omega.) having a same angular frequency as that of the AC electric field, and a second component (E.sub.2 .omega.) having an angular frequency which is two times that of the AC electric field. Then, a ratio (E.sub.2 .omega./E.omega.

Abstract: A spatial light modulating element including an electrooptic and photoconductive single crystal plate, a light-transmitting insulating layer provided on at least one of opposite surfaces of the electrooptic and photoconductive single crystal plate, and a pair of electrodes provided for applying an electric field to the insulating layer and the single crystal plate. The insulating layer is formed from a uniaxial single oxide crystal which is crystallographically oriented such that the insulating layer exhibits neither birefringence, nor an electrooptic effect in a direction of the electric field. The insulating layer may be a LiNbO.sub.3, LiTaO.sub.3 or TiO.sub.2 (rutile) single crystal plate cut normal to the (001)-axis.

Abstract: An instrument including a light-emitter for emitting a light beam, a sensing head portion through which the light beam is transmitted, a light-detective element receiving the beam from the head portion, and a detector receiving an electric signal from the light-detective element. The head portion has a thermo-optical element for changing a first component of the light beam with an ambient temperature, and an optical element for changing a second component of the beam with an electric quantity. The electric signal produced by the light-detective element has a first and a second component which correspond to the first and second components of the light beam, respectively. The detector determines the ambient temperature based on the first component of the electric signal, and determines the electric quantity based on the second component of the electric signal. The electric quantity may be an AC magnetic field, a current, an AC electric field or a voltage.

Abstract: An optical unit including a first electrooptical crystal element having a pyroelectric effect and first polarized faces, and a second electrooptical crystal element having a pyroelectric effect and having second polarized faces corresponding to the first polarized faces. The first and second polarized faces are electrically connected to each other such that a polarity of an electrical charge on each of the first polarized faces is opposite to that of an electrical charge on a corresponding one of the second polarized faces. The first electrooptical crystal element is positioned such that a light beam is propagated through the first electrooptical crystal element.

Abstract: An optical device including an optical bench and a plurality of optical elements. The optical bench has first and second supporting sections, separated from each other, each having at least two supporting surfaces. The optical elements secured to the first and second supporting sections have cylindrical bodies, so that these optical elements contact the sections only by lines. Therefore, the relative positions of each optical elements in the optical device are maintained for a long time without being affected by temperature variation in the atmosphere surrounding the optical device.

Abstract: A system for optically measuring the strength of an AC magnetic field, by an apparatus which includes a sensing head having a magnetooptical element, a polarizer and an analyzer, a light source device for producing a light beam to be transmitted through the sensing head, and a light-sensitive device for converting an optical output of the sensing head into an electric signal. The light beam is modulated by the sensing head to provide the optical output indicative of the strength of the AC magnetic field to which the magnetooptical element is exposed. The magnetooptical element is exposed also to a reference magnetic field different from the AC magnetic field, to thereby bias the light beam while being transmitted through the magnetooptical element. A first and a second component (E.omega.) and (E.sub.2 .omega.) of the electric signal is produced by the light-sensitive device. The first component (E.omega.) has the same angular frequency as that of the AC magnetic field, while the second component (E.sub.2 .

Abstract: A method and an apparatus for measuring the strength of an AC electric field or an equivalent voltage, or the strength of an AC magnetic field or an equivalent current, based on a light beam which is transmitted through and thus modulated by an optical sensing head due to the Pockel's and Faraday effects, while the sensing head is exposed to the AC electric and magnetic fields. The sensing head includes an optical material which exhibits the Pockel's effect and an optical material which exhibits the Faraday effect, or includes an optical material which exhibits both the Pockel's and Faraday effects. The modulated beam is applied to a light-sensitive element, which produces an electric output signal. A first and a second component of the electric output signal are retrieved by respective detectors. The first component has a same frequency as that of the electric or magnetic field, while said second component has a frequency which is two times that of said electric or magnetic field.

Abstract: An apparatus for detecting an accident of electric wire lines a single light emitting element, a plurality of optical sensor heads arranged respectively to the lines to be observed, for modulating a light supplied form the light emitting element through a light transmission line in response to electric variations in the line, and a single light receiving element for receiving the synthetic light. Therefore, since the light transmission line is used instead of electric wires, the apparatus has good insulation characteristics and thus the apparatus is not affected by an electromagnetic induction from the electric wire lines. Moreover, since use is made of single light emitting element and single light receiving element, high S/N ratio is realized.