Abstract: An optical device has multilayer films formed by periodically laminating a number of layers each comprising at least two kinds of optical crystal thin films (f.sub.n, g.sub.n) having different refractive indices onto a substrate. The multilayer films include a semiconductor material having a large non-linear optical coefficient as a composing material and have artificial optical anisotropy. Since the multilayer films of the optical device have a large non-linear coefficient and optical anisotropy, a non-linear phenomenon such as second-harmonic generation or the like can be efficiently caused.

Abstract: An ion beam (113) focused into a diameter of at most 0.1 .mu.m bombards substantially perpendicularly to the superlattice layers of a one-dimensional superlattice structure and is scanned rectilinearly in a direction of the superlattice layers so as to form at least two parallel grooves (108, 109, 110, 111) or at least two parallel impurity-implanted parts (2109) as potential barrier layers, whereby a device of two-dimensional superlattice structure can be manufactured. At least two parallel grooves (114, 115, 116, 117) or impurity-implanted parts are further formed orthogonally to the potential barrier layers of the two-dimensional superlattice structure, whereby a device of three-dimensional superlattice structure can be manufactured. In addition, deposition parts (2403, 2404, 2405) may well be provided by further depositing an insulator into the grooves (108, 109, 110, 111, 114, 115, 116, 117) which are formed by the scanning of the ion beam.

Abstract: The present invention provides a waveguide type optical switch which has a high extinction ratio and can be driven efficiently at a low voltage or a low current injection. Where the waveguide type optical switch is used as a reflection type optical switch, the switch section is of current confinement structure, and where it is used as a directional coupler type optical switch, the pn junction is formed in the position where the optical electric field takes the maximum value for the fundamental mode of the light propagating in the waveguide.

Abstract: An optical waveguide comprising a layer formed on a substrate, having a mixed composition of silicon oxide and silicon nitride and having an arbitrary value of refractive index ranging between those of the silicon oxide and the silicon nitride. The layer of said mixed composition can be formed on the substrate to easily fabricate the optical waveguide of the present invention by conducting a sputtering method employing a Si target and controlling the composition of a sputtering gas composed of a mixture of N.sub.2 and O.sub.2 gases.

Abstract: An optical switch wherein a stripe layer of a compound semiconductor whose refractive index is changed by changing a carrier concentration thereof is disposed so as to cut off both optical waveguides at a position of a longer diagonal line of an intersection portion between the optical waveguides formed on a substrate of a compound semiconductor and intersecting each other at a predetermined angle, and the refractive index is changed by causing current to flow to the stripe layer.

Abstract: An optical waveguide obtained by forming on a substrate an amorphous silicon film which contains a predetermined quantity of at least one of the elements of hydrogen, nitrogen and oxygen so that the amorphous silicon film has a predetermined value of refractive index. The optical waveguide can be made easily by carrying out a sputtering operation, in which Si is used as a target with a mixed gas of argon and at least one of hydrogen, nitrogen and oxygen, or a mixed gas of hydrogen and at least one of nitrogen and oxygen used as a sputtering gas, the composition of the sputtering gas being controlled in a predetermined manner during the sputtering operation.

Abstract: The present invention relates to an improvement in the optical transmission characteristics of a ridged type of optical waveguide in an optical integrated circuit. The invention is directed to reducing the effects of irregularities in the ridge sides on the optical transmission losses of the optical waveguide. According to the present invention, therefore, a hardened film of a heat-resistant, high-molecular resin is applied over the ridges and the optical waveguide, greatly reducing the optical transmission losses in the optical waveguide. An appropriate thickness of the heat-resistant, high-molecular resin film is between 200 to 1,000 nm, in consideration of the electric and magnetic fields applied thereto for the operation of the circuit. The present invention makes it possible to provide an optical integrated circuit with an optical waveguide which has low optical transmission losses.

Abstract: A spouted bed granulation process in which the average particle size of the final product is controlled by employing, as seed particles fed to the granulator, a mixture of particles of at least two different average particle sizes and changing the mixing ratio of the respective particles.

Abstract: Disclosed is a process for concentrating aqueous urea solutions in which an aqueous urea solution is allowed to flow as a falling film in countercurrent contact with a stream of hot inert gas to concentrate it to 95-99% by weight and the aqueous urea solution so concentrated is then passed through a packed zone in cocurrent contact with a stream of hot inert gas to concentrate it to not less than 99.5% by weight.

Abstract: A method for producing an optical fiber comprises (i) the step of depositing a barrier layer on the inner wall surface of a glass tube by the CVD (chemical vapor deposition) process, said barrier layer being capable of preventing the diffusion of impurities and being made of high-silica glass which has a refractive index that is substantially equal to that of the glass tube and which contains at least one substance for lowering the refractive index of silica and at least one substance for raising the refractive index of silica, (ii) the step of depositing a glass film of desired refractive index on the barrier layer by the CVD process, (iii) the step of heating and collapsing the resultant glass tube into a composite rod or the so-called optical fiber preform, and (iv) the step of heating and drawing said optical fiber preform into the optical fiber, whereby the optical fiber which has the impurity diffusion-preventing layer between the core and the outside glass layer can be easily produced.

Abstract: A method of producing an optical fiber comprising (i) the step of depositing a glass film of desired refractive index onto the inner wall surface of a quartz tube by the CVD (chemical vapor deposition) process, (ii) the step of heating the quartz tube to a high temperature while the gas of a compound which forms an oxide, enhancing the refractive index of the glass film, in an oxidizing atmosphere at the high temperature is kept flowing into the quartz tube along with an oxidizing gas, (iii) the step of heating and collapsing the quartz tube into a solid rod or the so-called preform, and (iv) the step of heating and drawing the optical fiber preform into the optical fiber.In the optical fiber produced by this method of manufacture, the lowering of the refractive index of the central part of the optical fiber is sharply reduced.

Abstract: In order to expand the product between the transmission length and the transmission bandwidth of an optical fiber for use in the optical communication and to facilitate the connection between the optical fibers, the optical fiber is made of transparent materials of three concentric layers of a core whose refractive index gradually decreases in the radial direction from the center, an intermediate layer which has a uniform refractive index lower than the varying refractive index of the core, and a cladding which has a uniform refractive index substantially equal to the lowest refractive index of the core.

Abstract: An information is written or erased in such way that, while a memory employing electrooptic ceramics wherein a ferroelectric phase and an anti-ferroelectric phase (or paraelectric phase) coexist having a morphotropic phase boundary is being heated to a temperature at which the polymorphic base boundary of the ceramic material occurs, an electric field opposite in polarity to the spontaneous polarization of the memory is applied to the material.According to the writing or erasing method, the writing of the information into the memory employing the material or the erasure of the information can be perfectly performed.

Abstract: A C-shaped resilient housing for encompassing at least three sides of an escalator belt and biasing a solution bearing pad into continuous abutment with the escalator belt. Ribs interior to the housing and flanges exterior to the rear of the housing may be included to hold the pad in place.