Abstract: In a magnetic recording medium (10) including a glass substrate (1) which has a principal surface and which includes a compressive stress layer (1aa) as a surface layer having the principal surface, and a magnetic layer (4) formed on the principal surface of the glass substrate, compressive stress produced on the principal surface of the glass substrate is equal to 3 kg/mm2 or more. The glass substrate has the principal surface provided with a texture (100) for inducing magnetic anisotropy in the magnetic layer. A distance from the principal surface of the glass substrate to the magnetic layer is equal to 1200 angstroms or less.

Abstract: In a method of manufacturing a chemical reinforced glass substrate, consideration is previously made about a relationship between conditions of chemical reinforcement for a glass substrate and deformation caused by the chemical reinforcement at an edge portion of the glass substrate. The glass substrate is chemically reinforced on the basis of the relationship so that an edge profile is shaped into a desirable edge profile during the chemical reinforcement. The resultant chemical reinforced glass substrate is flat and smooth in a wide area and effective to improve a recording density and to avoid head crashes.

Abstract: In a method of manufacturing a chemical reinforced glass substrate, consideration is previously made about a relationship between conditions of chemical reinforcement for a glass substrate and deformation caused by the chemical reinforcement at an edge portion of the glass substrate. The glass substrate is chemically reinforced on the basis of the relationship so that an edge profile is shaped into a desirable edge profile during the chemical reinforcement. The resultant chemical reinforced glass substrate is flat and smooth in a wide area and effective to improve a recording density and to avoid head crashes.

Abstract: A method of producing a substrate for an information recording medium in which there is a step of washing and drying the substrate, which is also subjected to precision polishing. In the method, a correlation is preliminarily obtained between a contact angle of water on a surface of the substrate before the washing/drying step and a size (height) of protrusions attached to the surface of the substrate during the washing/drying step. The contact angle of water on the surface of the substrate before the washing/drying step is controlled so that the protrusions have a size (1) so as not to cause a hit when at least a recording layer is formed on the surface of the substrate and when a slider provided with a recording device and/or a reproducing device is made to run on a surface of the information recording medium, and (2) so as not to cause an error upon recording and/or reproducing the information recording medium.

Abstract: In a method of producing a substrate for an information recording medium, the method including a washing/drying step of washing and drying said substrate subjected to precision polishing, a correlation is preliminarily obtained between a contact angle of water on a surface of the substrate before the washing/drying step and a size (height) of protrusions attached to the surface of the substrate during the washing/drying step. The contact angle of water on the surface of the substrate before the washing/drying step is controlled so that the protrusions have the size so as not to cause a hit when at least a recording layer is formed on the surface of the substrate to produce the information recording medium and when a slider provided with a recording device and/or a reproducing device is made to run on a surface of the information recording medium.

Abstract: A Mach-Zehnder optical modulator with an output light monitoring function whereby emitted light from the modulator is monitored for controlling a DC bias voltage applied between a first and a second electrode provided on a first and a second branch optical waveguide. The end face of the waveguide substrate on the output side is obliquely formed and an optical waveguide is provided on the waveguide substrate for taking out reflected light from the output end face as monitor light. A photodetector for detecting the monitor light is attached to the side face of the waveguide substrate. By such arrangement, the length of the waveguide substrate can be made shorter than that in the prior art. As an alternative, such an arrangement may be made that a double refraction crystal for separating monitor light is attached to the end face on the output side of the waveguide substrate and a prism for correcting optical path is attached to the double refraction crystal.

Abstract: An optical waveguide device which can be connected with an optical fiber through a simple positioning adjustment. The optical waveguide device comprises a substrate, a first cladding with a uniform thickness formed on the substrate, a core formed on the first cladding, a recognizable thin layer formed on the first cladding on both sides of the core, and a second cladding formed on the first cladding so as to cover the core. The thin layer is parallel to the top surface of the substrate and defines a reference plane which is substantially in the same plane as the bottom surface of the core. Connection of the optical waveguide device with the optical fiber is achieved by bringing the reference plane into contact with a plane which is in a predetermined relative position to the optical fiber and only making a planar positioning adjustment with the planes held in contact.

Abstract: A ferrule having an optical fiber connected thereto and a spherical lens are fixed in a cylindrical lens holder to form a fiber collimator. The thickness of a cylindrical wall of the lens holder is made smaller at a spherical lens receiving portion than the other portion and the cylindrical lens holder is fixed to a substrate by welding. A pair of such fiber collimators are provided in an opposing relationship to each other on the substrate, and an optical function element is disposed between the opposing fiber collimators to form an optical device. By provision of a light path changing over mechanism as such optical function element, an optical switch of a small size having a high performance can be provided.

Abstract: A semiconductor laser module comprising a serial arrangement of a laser assembly for emitting a substantially collimated beam of light, an optical isolator assembly having an optical isolator housed in a tubular package for transmitting the collimated beam of light with less loss in a forward direction than in a reverse direction, and an optical fiber assembly having a lens for converging and directing the beam from the optical isolator assembly into an optical fiber. There is also disclosed a method of optimizing the forward loss and isolation characteristics of the optical isolator assembly through adjustment of its angular position about its optical axis which is set at an angle to that of the laser assembly. For such adjustment, not only the isolator assembly is made rotatable relative to the laser assembly, but also the optical isolator itself is made rotatable within limits relative to the tubular package of the isolator assembly.

Abstract: An optical branching filter branches or mixes lights of n-kind of wavelengths. An input/output port for the light mixed n-kind of wavelengths is provided to one of two surfaces of the transparent block and second input/output parts for forming optical filters allowing only the lights having the predetermined wavelengths to pass therethrough, respectively among the lights in n-kind of wavelengths, but reflecting the lights having other wavelengths, respectively is provided to any one of two surfaces. A first input/output port and n second input/output ports, respectively is formed by an optical waveguide and a lens which optically connects the optical waveguide and first input/output part or a second input/output part. Positions of each second input/output port are selected so that the length of optical paths formed between the lenses of the first input/output port in the second input/output port are in the reverse proportion to the lengths of wavelengths corresponding to the second input/output portions.