Abstract: A wavelength-tunable semiconductor laser of distributed feedback (DFB) type wherein a diffraction grating having periodic corrugations along the direction of travel of light is formed on an active layer of at least one of layers adjacent thereto. An electrode on one side is separated into four or more electrodes in the direction of the cavity of the laser. Nonadjoining ones of them are electrically connected to form two electrode groups. The total length of first regions corresponding to a first one of the two electrode groups is larger than the total length of second regions corresponding to the second electrode group. The refractive indexes of the first regions are changed through current injection change to the first electrode group to vary the lasing wavelength and the gain of the second regions is controlled through current injection to the second electrode group, thereby generating output light of a constant output power and a variable single wavelength.

Abstract: An avalanche photo diode in which the guard ring portion and the front of the pn junction of the light receiving portion are formed at the same depth from the surface of an InP layer, so that the guard ring performs its desired function.

Abstract: A quantum well structure is disclosed, which is comprised of a quantum well layer of a thickness substantially equal to the de Broglie wavelength of electrons and carrier confinement layers of an energy gap greater than that of the quantum well layer. A second material of a lattice constant different from that of a first material primarily for the quantum well layer is disposed in the quantum well layer to provide a phase shift in the period of the crystal lattice of the first material, thereby forming energy levels in the forbidden band of the quantum well layer. A semiconductor device which employs such a quantum well structure and is so constructed as to utilize its physical phenomenon which is caused by the energy levels in the forbidden band. In concrete terms, the present invention has its feature in allowing ease in the fabrication of an intermediate infrared or blue light emitting device, for instance.

Abstract: An optical modulating device is disclosed which has, on a substrate directly or via a lower cladding layer, an optical waveguide layer, an upper cladding layer of a refractive index smaller than that of the optical waveguide layer and a pair of electrodes for applying an electric field across the substrate and the upper cladding layer and in which the absorption coefficient for incident light of a fixed intensity incident to the optical waveguide layer is varied by the electric field applied across the pair of electrodes to perform the modulation of the light and the modulated light is emitted from a light emitting end face of the optical waveguide layer. In accordance with the present invention, a pn junction is formed in the upper cladding layer and at least one buffer layer of an energy gap smaller than that of the upper cladding layer but larger than that of the optical waveguide layer is interposed between the upper cladding layer and the optical waveguide layer.

Abstract: A distributed feedback semiconductor device is disclosed which has a diffraction grating disposed near a light emitting active layer, a double hetero structure with the active layer sandwiched between n- and p-type semiconductors and n- and p-side electrodes for injection a current into the active layer, one of the n- and p-side electrodes being divided into a plurality of electrodes, and in which a current is injected into the active layer across the n- and p-side electrodes for laser oscillation to obtain output light. A first current source is connected to each of electrodes into which one of the n- and p-side electrodes is divided, and a second current source is connected to the divided electrodes via resistors, for injecting a current into the active layer in a desired ratio. The first and second current sources are controlled in accordance with the light emitting state of the active layer.

Abstract: An infrared emitting device for use in the 2 to 3 .mu.m region, which is low in the threshold current and operates over a wide temperature range. In accordance with the present invention, an InP substrate is employed in place of GaSb substrate and InAs substrate heretofore employed for the 2 to 3 .mu.m infrared semiconductor lasers. Moreover, as active layers or clad layers, one of more semiconductor layers are employed which differ in lattice constant from the InP substrate.

Abstract: A semiconductor optical amplifying element is disclosed which has a semiconductor multilayer structure including at least a first semiconductor layer for providing an optical gain in response to the injection of carriers thereinto, and a p-side electrode and an n-side electrode for the carrier injection. A first reflecting surface and a second reflecting surface are disposed thickwisely of the semiconductor multilayer structure and opposite to each other thereacross. The element is designed so that light incident thereon from the thickwise direction of the semiconductor multilayer structure is amplified by propagating through the element perpendicularly to the thickwise direction of the semiconductor multilayer structure while being multiple-reflected between the first reflecting surface and the second reflecting surface.

Abstract: There is here provided a convenient bag used at the time when microorganisms which adhere to a specimen containing a solid material are extracted with a saline solution and are then examined. In this bag, a filter sheet is stuck to plastic film sidewalls so as to extend from the opening inlet to the bottom portion of the sidewalls, so that the bag is divided into two chambers. A specimen and a saline solution are poured into one of the two chambers, and the resulting extract is taken out by a pipet from another chamber.

Abstract: A variable-waveguide optical branching filter is disclosed, in which a diffraction grating is formed in the cross region of two crossing waveguides, only light of a particular wavelength which is determined by the period of the diffraction grating is branched to a desired one of the waveguides, and the refractive index of the cross region is changed by control of a voltage or a current, or by way of irradiation with light, thereby changing the wavelength of light to be branched.

Abstract: A semiconductor laser is disclosed in which a light emitting region having a light emitting layer and a waveguide region having a waveguide layer which is coupled to at least one side of the light emitting layer with a high efficiency are integrated on the same substrate; the light emitting region includes an active filter section having a diffraction grating equipped with a band-pass filter function; the light emitting region and the waveguide region are electrically isolated and are each provided with an electrode; and the oscillation wavelength of the semiconductor lase is changed by changing the refractive indices of at least the waveguide region and the active filter section through voltage application or current injection to the electrodes, thereby producing a narrow-linewidth, single-wavelength oscillation output light of a wavelength which corresponds to the transmission wavelength of the active filter section determined by the preset refractive indices of the waveguide region and the active filter se

Abstract: A method is disclosed for manufacturing a diffraction grating formed by corrugations reversed in phase between a first region and a second region through use of two kinds of photoresists of opposite photosensitive characteristics. An isolation film is introduced for preventing the photoresists from getting mixed with each other, permitting the combined use of any photoresists. A step may be further included in which the isolation film is deposited on one of two kinds of photoresist films in at least one of a first region and a second region, is subjected to two-beam interference exposure, is removed and then a degraded layer, which is formed in the surface of the above said one kind of photoresist film during the deposition of the isolation film, is removed.

Abstract: A distributed feedback semiconductor laser with monitor is disclosed, in which the energy gap of a light absorbing layer provided on the window region alone is smaller than the energy gap of the light emitting layer, and in which an independent pn junction isolated from the pn junction in the laser region is provided in or at one edge of the light absorbing layer on the window region.

Abstract: An optical waveguide switch is disclosed in which at least two optical waveguides intersect at a predetermined angle to each other to provide, on both sides of the intersection region, input side optical waveguide regions for receiving incident light and output side optical waveguide regions for outputting guided light, and in which the incident light is input into one of the input side optical waveguide regions and is output from a desired one of the output side optical waveguide regions. In accordance with the present invention, an optically nonlinear material whose refractive index undergoes a substantial variation, depending on the intensity of incident light, is disposed in the intersection region. A loop is provided in association with a corresponding one of the input side optical waveguide regions for essentially branching the guided light in the corresponding waveguide output side optical waveguide region for feedback to the corresponding input side optical waveguide region.

Abstract: An optical switch is disclosed in which a switching section for switching the optical path of an incident light is formed in a region where two semiconductor optical waveguides cross each other. The switching section is composed of n-, i-, p-, i- and n-type semiconductor layers laminated in that order, each i-type layer being formed by a superlattice layer composed of a plurality of semiconductor thin films so that the i-type layer is higher in the effective refractive index and smaller in the effective energy gap than each n-type layer. The impurity concentrations of the n-, i-, p-, i-, and n-type layers and the thicknesses of the i-, p-, and i-type layers are determined so that the i-, p- and i-type layers are depleted in a thermal equilibrium state.

Abstract: An avalanche photo diode in which the guard ring portion and the front of the pn junction of the light receiving portion are formed at the same depth from the surface of an InP layer, so that the guard ring performs its desired function.

Abstract: An avalanche photodiode with a quantum well layer in which a thin film, periodic multilayer structure composed of two different semiconductors is formed in a carrier multiplying region, the effective ionization coefficient ratio of carriers is raised by a quantum well layer formed by the thin film, multilayer periodic structure, and only electrons of large ionization coefficient are injected into the multiplying region, thereby to reduce noise in the APD.

Abstract: A semiconductor photo detector provided with a photo detecting portion, in which at least three semiconductor layers of the same conductivity type and different energy gaps are formed in the order of magnitude of the energy gap, and in which another semiconductor layer which has the same composition as a first semiconductor layer having the largest energy gap among the at least three semiconductor layers but is different in conductivity type from the first semiconductor layer is formed in contact with the first semiconductor layer at the optical input side of the semiconductor photo diode.

Abstract: A distributed feedback semiconductor laser, in which the periodic corrugations in the first region and the second region of the light emitting region of the DFB laser have different lengths or depths to make the intensities of the Bragg reflection of the first region and the second region different from each other, thereby obtaining asymmetrical light outputs from the both sides of the DFB laser.

Abstract: A semiconductor device, which is formed by a sequential lamination of a first semiconductor layer having a carrier concentration more than 10.sup.17 cm.sup.-3, a second semiconductor layer having a carrier concentration less than 10.sup.16 cm.sup.-3, a third semiconductor layer having a carrier concentration more than 10.sup.17 cm.sup.-3 and a thickness less than 300 .ANG., a fourth semiconductor layer having a carrier concentration less than 10.sup.16 cm.sup.-3, and a fifth semiconductor layer having a carrier concentration more than 10.sup.17 cm.sup.-3 and, in which the first and fifth semiconductor layers are the same in conductivity type and the third semiconductor layer is different in conductivity type from the fifth semiconductor layer. In accordance with the present invention, the energy gap of the third semiconductor layer is larger than the energy gaps of the second and fourth semiconductor layers.

Abstract: A distributed feedback semiconductor laser, in which a DFB region is formed by a plurality of first semiconductor layers and a plurality of second semiconductor layers larger in energy gap than the first semiconductor layers which are alternately arranged on a substrate with a period for developing a Bragg reflection at a desired wavelength. A p-type region is formed in a part of the DFB region in a manner to provide a plane of junction across the plurality of first semiconductor layers and the plurlaity of second semiconductor layers while an n-type region is formed in the remaining part of the DFB region. The plurality of first semiconductor layers and the plurality of second semiconductor layers are alternately deposited to form the DFB region.