Abstract: A semiconductor laser device comprising an active layer, a layer furnished with a diffraction grating and formed in the vicinity of said active layer, and another layer formed on said layer with the diffraction grating and having a refractive index smaller than that of said active layer but greater than that of said layer with the diffraction grating.

Abstract: A distributed feedback semiconductor laser device comprising a laser oscillation region and a distributed reflector which are provided in a laminated crystal structure, and comprising facets at both the ends, wherein a light emitting face is disposed at one or both ends of the laser oscillation region, the face being parallel to the lamination direction and intersecting with the light emitting direction at an angle which is 90 degrees minus the Bresster angle.

Abstract: A buried type semiconductor laser device comprising a multi-layered epitaxial growth crystal including a striped laser-oscillation operating area on a semiconductor substrate, wherein said laser-oscillation operating area contains a buffer layer having the same polarity as said substrate, an active layer and a cladding layer having a polarity different from that of said substrate, said laser-oscillation operating area being sandwiched between one part of the burying layer and another part of the burying layer, which are disposed on said substrate and which have a polarity different from that of said substrate, through said substrate or a diffusion region having an impurity with the same polarity as said substrate so as to electrically isolate said burying layer from said cladding layer, thereby maintaining ineffective current flowing from said cladding layer to said burying layer at a low level even when current injected into said device is increased.

Abstract: A buried type semiconductor laser device comprising a multi-layered epitaxial growth crystal including a striped laser-oscillation operating area on a semiconductor substrate, wherein said laser-oscillation operating area contains a buffer layer having the same polarity as said substrate, an active layer and a cladding layer having a polarity different from that of said substrate, said laser-oscillation operating area being sandwiched between one part of the burying layer and another part of the burying layer, which are disposed on said substrate and which have a polarity different from that of said substrate, through said substrate or a diffusion region having an impurity with the same polarity as said substrate so as to electrically isolate said burying layer from said cladding layer, thereby maintaining ineffective current flowing from said cladding layer to said burying layer at a low level even when current injected into said device is increased.

Abstract: An optical device comprising a transparent plate having planar first reflecting surface and second reflecting surface, a reflector and a screen for forming interference fringes thereon. When a beam is incident on the transparent plate, a portion of the beam is reflected from the first reflecting surface, while the other portion of the beam enters the interior of the plate and is reflected at the second reflecting surface. The beam reflected from the first reflecting surface and further reflected from the reflector and the beam reflected at the second reflecting surface are superposed on the screen to produce interference fringes. The period of the interference fringes is easily variable by rotating the reflector and the screen around the line of their intersection.

Abstract: A light modulator for modulating data signal to high frequency light signal includes a semiconductor laser diode having an input for receiving the data signal and an output for producing a laser beam, a light detector for receiving the laser beam and producing an electric signal representing the laser beam, and an electric passage between the light detector and the input of the semiconductor laser diode so as to define a positive feedback circuit for feeding the output of the semiconductor laser diode to the input of the same, whereby an oscillation at a resonance frequency is effected in the semiconductor laser diode to generate a light modulated high frequency laser signal from the semiconductor laser diode.

Abstract: A method for the formation of a diffraction grating on a substrate using a holographic technique and an etching technique, wherein the periodicity of the pattern of the diffraction grating can be changed at will by a change of the light-path length of one of the two light fluxes from a holographic exposing system.

Abstract: A micro-displacement measuring apparatus using a semiconductor laser, comprises a compound resonator system containing the semiconductor laser, and a light detector receiving a light from said semiconductor laser. The compound resonator system is constructed such that a light from the semiconductor laser irradiates an object to be measured and the reflected light therefrom returns to the semiconductor laser, wherein the relationship between the reflectivity R.sub.f at the front facet of the semiconductor laser from which a laser light irradiates the object, and the reflectivity Rr at the rear facet of the semiconductor laser which is opposite the front facet is as follows: 0.1<R.sub.f Rr<1.

Abstract: A distributed feedback semiconductor laser device with a resonator comprising a multi-layered optical waveguide that contains an optical guiding area with a periodic corrugation, the optical guiding area being composed of at least two regions, a first region I and a second region II, wherein both the periodicity of the corrugation and the depth of each concave portion of the corrugation of the first region I of the optical guiding area are the same as those of the second region II of the optical guiding area, and moreover the thickness of the first region I of the optical guiding area is the same as that of the second region II of the optical guiding area, so that the effective refractive index of the first region I in the resonator direction becomes the same as that of the second region II in the resonator direction and the Bragg wavelength is maintained at a fixed level in the the resonator direction; and there is a difference in their refractive index at the interface between the first and second regions o

Abstract: A semiconductor laser comprising a triple-layered structure composed of an active layer for laser oscillation and a pair of optical guiding layers sandwiching said active layer therebetween, wherein the refractive index of each of said optical guiding layers is smaller than that of said active layer, and the bandgap of each of said optical guiding layers is greater than that of said active layer, and moreover diffraction gratings with different pitches are positioned on the outer side of each of said optical guiding layers.

Abstract: A semiconductor laser device having a buried heterostructure which includes a multi-layered crystal structure, containing an active layer for laser oscillation, on a substrate, said multi-layered crystal structure having a striped mesa-portion, a multi-layered structure surrounding said mesa-portion and a burying layer disposed on an upper face of said striped mesa-portion. The unique structure results in a heterojunction at each side of the active layer.

Abstract: A semiconductor laser apparatus comprising a laser-oscillating area and a light-detecting area, both of which are formed on a single substrate, wherein said laser-oscillating area and said light-detecting area have a common semiconductor layer with a first polarity disposed on said substrate and a common active layer disposed on said semiconductor layer, and said layer-oscillating area of said laser-oscillating area and/or said light-detecting area has a cladding layer with a second polarity disposed on said active layer, said laser-oscillating area and said light-detecting area being separated by a groove formed from the upper face of said cladding layer to the region below said active layer, and the active layer of said laser-oscillation area being flat while the active layer of said light-detecting area is sloped.

Abstract: A semiconductor laser device comprising a GaAlAs first cladding layer, a Ga.sub.1-x Al.sub.x As (0.ltoreq.x.ltoreq.0.4) active layer for laser oscillation, an In.sub.1-y Ga.sub.y P.sub.1-z As.sub.z (z=2.04y-1.04, and 0.ltoreq.z.ltoreq.1) optical guiding layer with a diffraction grating thereon, a GaAlAs buffer layer disposed between said active layer and said optical guiding layer, and a GaAlAs second cladding layer, the width of the forbidden band of said buffer layer being greater than that of the active layer and smaller than that of the optical guiding layer.

Abstract: A semiconductor laser device for laser oscillation at a wavelength in the range of from 660 nm to 890 nm which includes an active layer of Ga.sub.1-x Al.sub.x As (0.ltoreq.x.ltoreq.0.4) or In.sub.1-y Ga.sub.y P.sub.1-z As.sub.z (0.51.ltoreq.y.ltoreq.1, 0.ltoreq.z.ltoreq.1, and z=2.04y-1.04) and a layer with a diffraction grating thereon of In.sub.1-y Ga.sub.y P.sub.1-z As (z=2.04y-1.04) which is adjacent to the active layer.

Abstract: A semiconductor laser includes a mesa-striped laser structure. A substrate has layered on it an active layer with a refractive index higher than that of, and with an energy gap smaller than that of the substrate. A first electrode is formed under the substrate. A cladding layer of a conductivity type different than that of the substrate overlays the active layer. A multilayered burying crystal includes, at the sides of the mesa-striped laser structure, successively first, second and third burying layers. The first and third burying layers are of the same conductivity type as the substrate. The second burying layer is of a conductivity type different from that of the substrate. A cap layer of a conductivity type different than the substrate covers the upper face of the mesa-striped structure and an upper face of the third burying layer. A second electrode is formed on the cap layer. Injected current flowing into a thyristor composed of the cap layer and the three burying layers can be suppressed.

Abstract: A distributed feedback semiconductor laser device comprising an active layer positioned between a first cladding layer and a second cladding layer, and an absorption layer positioned between the active layer and one of the cladding layers, the absorption layer having grooves to form a diffraction grating with a given periodicity in the direction of the propagation of laser light.

Abstract: A visible double heterostructure-semiconductor laser comprising an InGaAs, InAlP, InAlAs, InAlSb or InGaSb layer, a first cladding layer on the InGaAs, InAlP, InAlAs, InAlSb or InGaSb layer; an active layer on the first cladding layer and a second cladding layer on the active layer, wherein a mixed crystal of, respectively InGaAs, InAlP, InAlAs, InAlSb or InGaSb is used, as a substrate crystal for growing of said InGaAs, InAlP, InAlAs, InAlSb or InGaSb layer thereon, and the composition ratio of the substrate crystal and of each of the layers is selected so as to result in the approximate coincidence between the lattice constant of the substrate crystal and the lattice constant of each of these layers, an energy difference of 0.2 eV or more between the direct transition and the indirect transition within said active layer, and an energy difference of 0.2 eV or more between the active layer and either of the first or the second cladding layers.

Abstract: A method for producing a semiconductor laser device having a buried heterostructure includes a multi-layered crystal structure, containing an active layer for laser oscillation, on a p-substrate, said multi-layered crystal structure having a striped mesa-portion, a p-n-p multi-layered structure surrounding said mesa-portion and a burying layer disposed on an upper face of said striped mesa-portion. The unique structure results in a heterojunction at each of both side faces of said active layer in said mesa-portion.

Abstract: A semiconductor laser includes a current blocking layer formed on a substrate, a first cladding layer formed on the current blocking layer, an active layer formed on the first cladding layer, and a second cladding layer formed on the active layer. An indent is formed in the current blocking layer near the center of the laser element, and a V-shaped groove is formed in the current blocking layer across the indent. A gain guide structure is formed where the indent is formed, and an index guide structure is formed near the cleaved facet. A stable transverse mode laser emission is ensured without the influence of the return beam reflected from the disc surface, and the attendant mode competition noise is reduced.

Abstract: An apparatus for measuring the reflectivities of the resonator facets of a semiconductor laser when the facets are covered with a protective coating of dielectric material or the like, which comprises photodetector means for individually measuring the laser light powers from both facets of the resonator, reflector means for reflecting the laser light from one of the facets back to the laser, shutter means openable or closable at a position to block the laser light reflected from the reflector means, and photodetector means for measuring the power of the reflected laser light.