Abstract: A distributed feedback semiconductor laser selectively performs one of two oscillations in different polarization modes having different polarization planes. The laser includes a substrate, a light waveguide formed on the substrate, which at least partially includes an active layer, a diffraction grating formed around the waveguide, and an injecting unit for injecting a modulation current into a portion of the waveguide. The waveguide and the grating are constructed such that oscillation wavelengths of the polarization modes are different from each other and minimum values of threshold gain in the polarization modes near the Bragg wavelength are approximately equal to each other. The semiconductor laser can be driven by a minute modulation current and prevents degradation of response characteristics due to dynamic wavelength fluctuation in a high-frequency range when used in optical communication systems in which the switching of polarization mode is performed.

Abstract: An optical device includes an asymmetric dual quantum well (ADQW) structure which is comprised of a plurality (at least two) of different semiconductor quantum well layers coupled to each other. In the ADQW structure, the width of a deeper quantum well layer having a narrower band gap is made narrower than that of a less deeper quantum well layer having a wider band gap such that the shift of an exciton wavelength is scarcely caused due to the quantum confined Stark effect by the application of an electric field in a predetermined range. As a result, only a refractive index of the ADQW structure is changed, but an absorption factor is scarcely changed for a given range of wavelength by the application of the electric field. Further, there is provided a member for applying an electric field to the asymmetric dual quantum well structure.

Abstract: A tunable-filter control method or apparatus tracks a central wavelength in a transmission spectrum of a tunable-filter to a wavelength of light to be received. The central wavelength in the transmission spectrum of the tunable-filter is periodically and minutely modulated. An error signal is generated for use in tracking the central wavelength to the wavelength of the light to be received, by using a tunable-filter output which exhibits the effect of the minute modulation of the central wavelength. A tracking condition, which corresponds to one of a draw-in state and a stable state, is monitored to control the modulation of the central wavelength based on a result of the monitoring, so that a modulation amplitude of the central wavelength in the minute modulation is increased at the time of the draw-in state of the tracking condition and is decreased at the time of the stable state of the tracking condition.

Abstract: In optical communications, an optical receiver or semiconductor apparatus and an optical communication system using the semiconductor apparatus of the present invention solve the problem of polarization dependency. The optical receiver or optical semiconductor apparatus includes a pair of optical filters arranged such that tuned wavelengths for two different modes, e.g., tuned wavelengths for TE and TM modes, are set as light components having the same wavelength, and a beam splitting path for directing signal light to the pair of optical filters. Alternatively, the optical receiver or optical semiconductor apparatus includes a filter waveguide or waveguides capable of setting the tuned wavelength of one mode (e.g., TE) to be the same as the tuned wavelength of the other mode (e.g., TM) of two modes having different orders of transverse modes (e.g., two orthogonal modes), and an input waveguide. The input waveguide and filter waveguide are arranged to equally couple a signal light to those two modes.

Abstract: A semiconductor optical filter that includes a semiconductor substrate and a laser structure formed on the substrate. The laser structure includes an active layer of a quantum well structure and a grating formed along the active layer. The active layer is constructed to have a ground state level and an energy level other than the ground state level. A saturation gain of the ground state level is set to a value less than an internal loss, and the other energy level is set to permit an increase in the amount of carriers injected into the laser structure. The laser structure is typically a distributed feedback type laser structure. Anti-reflection coatings may be formed on the end surfaces of the laser structure.

Abstract: An optical semiconductor device with wavelength selectivity comprises a substrate, a collector layer provided on said substrate and composed of a semiconductor having a first conductive type, a multiple quantum well layer provided on said collector layer, a base layer provided on said multiple quantum well layer and composed of a semiconductor having a second conductive type, said base layer consisting of an active layer, and first and second semiconductor layers with said active layer sandwiched therebetween and having a wider band gap than said active layer, said base layer and said multiple quantum well layer propagating light, an emitter layer provided on said base layer and composed of a semiconductor having the first conductive type, and a collector electrode, a base electrode and an emitter electrode electrically connected to said collector layer, base layer and emitter layer, respectively.

Abstract: A Bloch line transferring method or system comprises a step of transferring only a first Bloch line of the Bloch line pair in the magnetic wall in a predetermined direction, and a step of transferring a second Bloch line of the Bloch line pair in the predetermined direction to form the Bloch line pair. It typically comprises applying a magnetic field perpendicular to a film plane of a magnetic thin film having the magnetic wall, to the magnetic thin film, and applying a magnetic field parallel to the film plane of the magnetic film, to the magnetic thin film along the magnetic wall.

Abstract: A transfer method for transferring Bloch lines present in the magnetic wall of a magnetic section formed in a magnetic thin film along the magnetic wall includes the steps of distributing a predetermined soft magnetic material layer pattern on the magnetic thin film, applying a magnetic field to the soft magnetic material layer pattern parallel to the film surface of the magnetic thin film to form a potential well in the magnetic thin film, positioning the Bloch lines in the potential well, and varying the direction of the magnetization of the soft magnetic material layer pattern in a plane parallel to the film surface to move the potential well along the magnetic wall and transfer the Bloch lines.

Abstract: A semiconductor laser element capable of changing an oscillation wavelength over a wide range without increasing a threshold current is disclosed. A wavelength selective filter capable of changing a selected wavelength over a wide range is also disclosed. The semiconductor laser element has a substrate and a laser resonator formed on the substrate by stacking semiconductor layers including an active layer and an optical waveguide layer of a superlattice structure. The resonator includes a first reflection portion, an active portion, a phase adjustment portion and second reflection portion which are juxtaposed in a resonance direction. Diffraction gratings are formed in the optical guide layer of the first and second reflection portions. Electrodes are independently formed in the active portion, the phase adjustment portion and the first and second reflection portions. Further, a method for driving the semiconductor laser is disclosed.

Abstract: Method for transferring the Bloch line present in the magnetic wall of the magnetic domain formed in the magnetic thin film, along the magnetic wall is characterized by the steps of forming a predetermined stress distribution along the magnetic wall in the magnetic thin film, positioning the Bloch line to a predetermined position in the magnetic wall in accordance with the stress distribution, and applying a pulsive magnetic field normally to a film plane of the magnetic thin film in synchronism with the formation of the stress distribution. The Bloch line is transferred from the predetermined position to another position by the stress distribution formation step and the magnetic field application step.

Abstract: A solid state memory device has a thin film for bubble memory, a laser light source, and optical means using a laser light emitted from the laser light source to cause information to be stored in the form of bubbles on the thin film for bubble memory and reproduce the stored information.

Abstract: In a method or device for detecting the presence and/or absence of a Bloch line in a magnetic wall of a magnetic domain formed in a thin magnetic film, a magnetic field parallel to the plane of the thin magnetic film is applied to the magnetic domain to cause a variation in the magnetic domain, the state of variation of the magnetic domain is detected and the presence and/or absence of a Bloch line in a predetermined position of the magnetic wall is detected according to the result of the detection of the state of variation set forth above.

Abstract: A wavelength selective filter capable of changing a selected wavelength over a wide range, andd a method for driving such a filter. The wavelength selective filter has a substrate and an optical waveguide layer including a superlattice structure on the substrate. The optical waveguide layer includes a reflection portion and an optical waveguide portion which are juxtaposed in a light propagation direction. A diffraction grating is formed in the reflection portion of the optical waveguide layer, and an electrode is formed in the reflection portion for applying voltage.

Abstract: There is disclosed a method of recording and/or reproducing in/from a Bloch line memory, including the step of: radiating or guiding a light beam to a vicinity of a distal end of a magnetic domain capabable of forming a Bloch line therein or on an extending line thereof.

Abstract: A magnetic memory has a substrate, a magnetic film provided on the substrate including a recording medium capable of producing a recording carrier, and a light waveguide layer on the magnetic film or on that surface of the substrate which is opposite to a surface on which the magnetic film is present. Recording and reproduction of information are effected relative to the magnetic film by a light propagated through the light waveguide layer.

Abstract: A magnetic record reproducing method includes the steps of bringing a magnetic film, capable of producing a magneto static wave, into intimate contact with or proximity to the recording surface of a magnetic recording medium, causing the magnetic film to produce the magnetostatic wave, detecting any variation in wave number in the magnetostatic wave attributable to the magnetized signal of the recording surface, and converting the variation in wave number in the magnetostatic wave into an electrical signal.

Abstract: A process for transferring Bloch lines formed in a magnetic wall of a magnetic domain and a magnetic memory apparatus for recording/reproducing information in utilizing Bloch lines formed in the magnetic wall of the magnetic domain as a information carrier are disclosed. The process comprises steps of forming a positive or negative magnetic charge area in the magnetic wall, thereby attaching a Bloch line to the area, and moving the magnetic charge area, thereby moving the Bloch line. The apparatus comprises a memory substrate having a stripe-shaped magnetic domain, a way to write Bloch lines in the magnetic wall of the stripe-shaped magnetic domain according to input information, a way to read the Bloch lines so stored to reproduce the information in the form of electric signals and a way to apply a rotating magnetic field parallel to the plane of the memory substrate, to the stripe-shaped magnetic domain, to move the Bloch lines along the magnetic wall.

Abstract: A method of transferring Bloch lines present in a domain wall of a magnetic domain formed in a thin magnetic firm, includes cyclically forming asymmetrical potential wells along the domain wall in order to locate the Bloch lines at predetermined positions of the domain wall, and applying a pulsed magnetic film to shift the Bloch lines from a predetermined potential well to another potential well. In a magnetic memory for recording information using Bloch lines as an information carrier, a memory substrate has a stripe magnetic domain defined by a domain wall along which asymmetrical potential wells are cyclically formed to stabilize the Bloch lines along the domain wall. The Bloch lines are written in the domain wall in accordance with input information, the Bloch lines so formed are read out, and the read-out Bloch lines are converted into an electrical signal.

Abstract: A method of treating an aqueous sodium sulfide solution, such as white liquor in kraft pulping systems, for the oxidation of the sulfide with oxygen in the presence of a specific activated carbon catalyst which is (a) a particulate activated carbon catalyst having an average particle diameter of 0.2-4 mm, a pore volume of at least 0.25 cc/g in pores with diameters of not smaller than 100 .ANG. and a pore volume of at least 35% of the total pore volume in pores with diameters of not smaller than 100 .ANG. or (b) a fibrous activated carbon catalyst having a specific surface area of 300-2500 m.sup.2 /g and an outer surface area of 0.1-5 m.sup.2 /g.

Abstract: A catalyst for hydrotreating a heavy hydrocarbon oil containing asphaltenes comprises a porous carrier composed of one or more inorganic oxides of at least one element selected from among those of Groups II, III and IV of the Periodic Table, and at least one catalytic metal component composited with the carrier. The metal of the catalytic metal component is selected from among those of Groups VB, VIB, VIII and IB of the Periodic Table. The catalyst contains about 1 to 30% by weight of such catalytic metal component and has the following pore characteristics with regard to its pores having a diameter of 75 .ANG. or more: an average pore diameter APD of about 180 to 500 .ANG., a total pore volume PV, expressed in cc/g, being equal to or greater than a value X ##EQU1## the volume of pores with a diameter of about 180 to 500 .ANG. being at least about 0.2 cc/g, the volume of pores with a diameter of at least 1,500 .ANG. being not greater than about 0.03 cc/g, and a total surface area being at least about 60 m.