Abstract: A waveguide of an optical device is formed by a ridge waveguide portion which is formed as a substantially stripe convex portion extending in a guiding direction, and a gain waveguide portion which guides light in a gain region optically coupled with the ridge waveguide portion. An extended portion is formed to extend from the gain waveguide portion in the lateral direction of the waveguide. With this extended portion, an electrode and a pad are connected by a planar structure on the flat surface continuing from the upper surface of the ridge waveguide portion, without using any resin step. A phase shift effect is also obtained in the gain waveguide portion.

Abstract: A transmitter and a receiver for wavelength division multiplexing optical transmission need no multiplexer and can be made compact and manufactured easily while promising a high reliability of a system using them. By using second-order Bragg diffraction gratings to form the output mechanism, a plurality of DFB laser-type elements can be integrated so that their optical outputs adversely affect each other. Therefore, a plurality of lasers can be arranged coaxially to form a light source for wavelength division multiplexing optical transmission without using a multiplexer. By using the same mechanism on the part of a receiver, a demultiplexer can be omitted.

Abstract: A burying-heterostructure (BH) type semiconductor laser having a constricted mesa which has an active region. The laser has two spaces, located above and below the active region, for constricting a current to reduce a leakage current. The laser further has a first group of columns extending through the space located above the active region, and a second group of columns extending through the space located below the space. The columns of the first group are staggered in a vertical plane, with respect to the columns of the second group.

Abstract: Disclosed are a semiconductor light emitting element whose temperature characteristics are compensated for so as to provide a stable temperature characteristics in a temperature range from -40.degree. C. to +85.degree. C., and an optical fiber transmission system using the same semiconductor light emitting element. In the semiconductor light emitting element, an active layer (2) is buried on an n-type InP semiconductor substrate (1) formed with an n-side electrode (21). The upper layers (4, 5) are covered with an insulating film (22). A p-side electrode (20) is formed on the uppermost layer of the semiconductor substrate so as to cover the insulating film (22). A relatively large metallic resistance element (30) whose resistance increases with increasing temperature is wired on the insulating film (22) as a shunt path, so as to compensate for the temperature characteristics of the semiconductor light emitting element.

Abstract: A GCL is formed on a first major surface of a semi-insulating InP substrate. Specifically, an InGaAsP active layer, an InGaAsP waveguide path and a striped grating having two phase shift portions are formed on the first major surface of the InP substrate. An EA modulator is formed on a second major surface of the semi-insulating InP substrate. Specifically, a p-InP layer, an MQW structure of 100-layer, an n.sup.- -InP layer and an n.sup.+ -InP layer are formed on the second major surface of the InP substrate. The first major surface and second major surface of the InP substrate are inclined to each other by a few degrees.

Abstract: A linear active layer, a current block layer and a clad layer are formed on the first major surface of a wafer, while a first electrode is formed on the second major surface of the wafer. A linear first opening is formed in the first electrode. The wafer exposed to the first opening is etched to form a first guide groove linearly extending in a direction perpendicular to the active layer. A second electrode is formed on the clad layer and etched to form a linear second opening therein. The clad layer, current block layer and wafer, located directly under the second opening, are etched to form a second guide groove thereon so as to extend in a direction parallel to the active layer. The wafer is cleaved along the first guide groove to form bars each having semiconductor lasers. The bars are arranged in parallel to one another and separated from one another by the second guide groove. The wafer is cleaved or cut along the second guide groove to obtain semiconductor chips.

Abstract: A distributed feedback semiconductor laser comprises a semiconductor substrate, a waveguiding structure, provided on the semiconductor substrate, including a diffraction grating, an active layer and a top layer for ohmic contact, a first electrode provided on the top layer, a second electrode attached to the semiconductor substrate, and means for compensating spatial nonuniformity of a carrier density caused by spatial hole burning. The means changes an electrical resistance between the first electrode and the active layer, corresponding to a spatial distribution of photon density along the waveguiding structure.

Abstract: A buried heterostructure type distributed feedback semiconductor laser comprises a semiconductor substrate transparent to an oscillation light beam, a laser stripe including a diffraction grating, an active layer, and a guiding layer formed on the semiconductor substrate, and semiconductor peripheral region formed so as to cover the laser stripe on the semiconductor substrate. The semiconductor peripheral region is transparent to an oscillation light beam. Rectangular grooves are formed near both sides of emission facet of the laser stripe more deeply than the laser stripe. Since a radiation mode from the laser stripe is reflected and scattered by the grooves, it cannot hardly reach the emission facet. Therefore, the radiation mode does not interfere with an output beam from the laser.

Abstract: A semiconductor laser chip comprises a semiconductor substrate, two laser stripes formed on the semiconductor substrate and each having a light waveguide path and a diffraction grating extending along the light waveguide path, and a groove for electrically isolating the laser stripes from each other. The facet phases of the diffraction grating at those facets of the plural laser stripes which are located at least in the same direction are different from each other. The diffraction gratings at the facets of two laser stripes comprise a plurality of grooves extending at an acute angle relative to the facets.

Abstract: Disclosed is a grating-coupled surface emitting laser capable of obtaining a beam with high directivity, structured by forming a light output window in a limited regions with high intensity radiations along the propagation direction. Its intensity distribution of radiation mode along the axis can be controlled by injecting a current independently into the multiply-divided electrodes or by pumping optically these electrodes independently. The control is, in principle, achieved by an equivalent change of the phase-shift of the gratings.

Abstract: A method of oscillating a continuous caster mold at high frequencies comprises disposing a plurality of oscillators having substantially the same oscillating characteristic at appropriate intervals along or in the vicinity of a line where liquid metal contacts an inner lining of a mold, connecting the tip of each oscillator to the inner lining so that the axis of the oscillator extends at right angles to the surface of the inner lining, and supplying power from an oscillation generator to each oscillator so that the oscillation frequencies of any two adjoining oscillators are differentiated within the limit of 2 KHz. Thus, any two adjoining oscillators oscillate the inner lining at right angles to the surface thereof at mutually differentiated frequencies.