Abstract: In a semiconductor laser device including having an index-guided structure and oscillating in a fundamental transverse mode, a lower cladding layer, a lower optical waveguide layer, a quantum well layer, an upper optical waveguide layer, and a current confinement structure are formed in this order. The thickness of the upper optical waveguide layer is smaller than the thickness of the lower optical waveguide layer. In addition, the sum of the thicknesses of the upper and lower optical waveguide layers may be 0.5 micrometers or greater. Further, the distance between the bottom of the current confinement structure and the upper surface of the quantum well layer may be smaller than 0.25 micrometers.

Abstract: A semiconductor laser includes a first clad layer having one of p-type conductivity and n-type conductivity, a first optical waveguide layer, a first barrier layer of GaAs1-y2Py2, a quantum-well active layer of Inx3Ga1-x3As1-y3Py3, a second barrier layer of GaAs1-y2Py2, a second optical waveguide layer and a second clad layer having the of p-type conductivity and n-type conductivity formed in this order on a GaAs substrate. Each of the first and second clad layers is of a composition which matches with the GaAs substrate in lattice. Each of the first and second optical waveguide layers is of a InGaAsP composition which matches with the GaAs substrate in lattice. Each of the first and second barrier layers is 10 to 30 nm in thickness and is of a composition which has tensile strain relative to the GaAs substrate, the product of the tensile strain and the thickness of each of the first and second barrier layers being 5 to 20% nm.

Abstract: In a semiconductor laser device, a GaAs substrate of a first conductive type, a lower cladding layer of the first conductive type, a lower optical waveguide layer made of InGaP of an undoped type or the first conductive type, an active layer made of InGaAsP or InGaAs, a first upper optical waveguide layer made of InGaP of an undoped type or a second conductive type, a second upper optical waveguide layer made of InGaP of an undoped type or the second conductive type, an upper cladding layer of the second conductive type, and a contact layer of the second conductive type are formed in this order to form a layered structure.

Abstract: In a semiconductor laser device, an active region includes alternating layers of at least one quantum well layer and a plurality of barrier layers, where two of the plurality of barrier layers are the outermost layers of the alternating layers, each of the at least one quantum well layer has a first thickness da and a compressive strain &Dgr;a, and each of the plurality of barrier layers has a second thickness db and a tensile strain &Dgr;b. In the active region, a strain buffer layer is formed between each quantum well layer and each of two barrier layers adjacent to the quantum well layer, where each strain buffer layer has a third thickness dr and an intermediate strain &Dgr;r which is between the compressive strain &Dgr;a and the tensile strain &Dgr;b.

Abstract: In a semiconductor laser device: an active layer; a first upper cladding layer of a first conductive type; a current confinement layer of a second conductive type; a second upper cladding layer of the first conductive type; and a contact layer of the first conductive type are formed above a GaN layer of the second conductive type. In the semiconductor laser device: a groove is formed through the full thickness of the current confinement layer so as to form an index-guided structure; the active layer is a single or multiple quantum well active layer formed by alternately forming at least one Inx1Ga1-x1N well and a plurality of Inx2Ga1-x2N barriers, where 0≦x2<x1<0.5; the current confinement layer has a superlattice structure formed with Ga1-z4Alz4N barriers and GaN wells, where 0<z4<1; the second upper cladding layer is formed over the current confinement layer so as to cover the groove; and the contact layer is formed on the entire upper surface of the second upper cladding layer.

Abstract: An index optical waveguide semiconductor laser is formed by a lower clad layer, a lower optical waveguide layer, an active layer, an upper optical waveguide layer and an upper clad layer superposed one on another in this order on a GaAs substrate. Each of the upper and lower clad layers and the upper and lower optical waveguide layers is of a composition which matches with the GaAs substrate in lattice. The upper optical waveguide layer is formed by an Inx2(Alz2Ga1−z2)1−x2As1−y2Py2 (1≧y2≧0.8) optical waveguide layer and a Ga1−z1Alz1As optical waveguide layer formed on the upper surface of the Inx2(Alz2Ga1−z2)1−x2As1−y2Py2 optical waveguide layer.

Abstract: A semiconductor laser device comprises a GaAs substrate, a first cladding layer having either one of p-type electrical conductivity and n-type electrical conductivity, a first optical waveguide layer, an In.sub.x2 Ga.sub.1-x2 As.sub.1-y2 P.sub.y2 first barrier layer, an In.sub.x3 Ga.sub.1-x3 As.sub.1-y3 P.sub.y3 quantum well active layer, an In.sub.x2 Ga.sub.1-x2 As.sub.1-y2 P.sub.y2 second barrier layer, a second optical waveguide layer, and a second cladding layer having the other electrical conductivity, the layers being overlaid in this order on the substrate. Each cladding layer and each optical waveguide layer have compositions, which are lattice matched with the substrate. Each of the first and second barrier layers has a tensile strain with respect to the substrate and is set such that a total layer thickness of the barrier layers may be 10 nm to 30 nm, and a product of a strain quantity of the tensile strain and the total layer thickness may be 0.05 nm to 0.2 nm.

Abstract: A III-V group semiconductor laser includes a first clad layer, a first optical waveguide layer, a first barrier layer, an active layer, a second barrier layer, a second optical waveguide layer and a second clad layer formed in this order on a GaAs substrate which is a III-V group compound semiconductor. Each of the first and second clad layers and the first and second optical waveguide layers is of a composition which matches with the GaAs substrate in lattice. The active layer is of a composition which induces compressive strain on the GaAs substrate. Each of the first and second barrier layers is of a composition which induces tensile strain on the GaAs substrate, thereby compensating for the compressive strain induced in the active layer. The ratio of V group elements contained in the first optical waveguide layer is the same as that in the first barrier layer, and the ratio of V group elements contained in the second optical waveguide layer is the same as that in the second barrier layer.

Abstract: A short wavelength laser includes a light source having a fundamental generating portion which emits fundamental wave and a wavelength convertor which converts the fundamental wave to its second harmonic. A light amplifier amplifies the second harmonic.

Abstract: A semiconductor laser includes a first clad layer, a first optical waveguide layer, a first barrier layer, an active layer, a second barrier layer, a second optical waveguide layer and a second clad layer formed in this order on a GaAs substrate which is a III-V group compound semiconductor. Each of the layers contains As and P, each of the first and second clad layers and the first and second optical waveguide layers is of a composition which matches with the GaAs substrate in lattice. The active layer is of a composition which induces compression strain on the GaAs substrate, and each of the first and second barrier layers is of a composition which induces tensile strain on the GaAs substrate, thereby compensating for the compression strain induced in the active layer.

Abstract: An integrated optics semiconductor laser device comprises, combined with one another, a light emitting section, a diffraction grating for controlling the wavelength of a produced laser beam, and an optical amplifier, which has a tapered portion, that confines a guided optical wave therein, and in which an optical wave is guided with refractive index wave guiding through an active medium. Unevenness is formed on side surfaces of the tapered portion, which side surfaces extend in a direction along which the optical wave is guided. The integrated optics semiconductor laser device can be controlled to produce a laser beam in the fundamental transverse mode even under the conditions for radiating a laser beam having a high intensity.

Abstract: A semiconductor laser comprises an active layer, optical waveguide layers formed on opposite sides of the active layer, and cladding layers. The active layer is constituted of an InGaAsP type of compound semiconductor. Each of the optical waveguide layers is constituted of an InGaAsP type of quarternary compound semiconductor, in which the content of As in the Group-V elements is at least 2%, or an InGaAlAsP type of five-element compound semiconductor, in which the content of As in the Group-V elements falls within the range of 2% to 10%. Each of the cladding layers is constituted of an InGaAsP type of quarternary compound semiconductor, in which the content of As in the Group-V elements falls within the range of 2% to 10%, or an InGaAlAsP type of five-element compound semiconductor, in which the content of As in the Group-V elements falls within the range of 2% to 10%.

Abstract: In a semiconductor laser, lower layers (an optical waveguide and a carrier blocking layer), which are exposed to air after they have been etched to form diffraction gratings until crystals are regrown, are formed of a five-element AlGaInAsP-based compound semiconductor material. Thus, a semiconductor laser is obtained which has a high yield and the oscillation wavelength range of 740-1000 nm and maintains a high reliability over a long period of time.

Abstract: An integrated phase-locked semiconductor laser wherein a plurality of waveguide paths extend in parallel to each other. A current blocking layer is formed on one of opposite major surfaces of a semiconductor substrate and is divided into a plurality of regions by a plurality of stripe-like channels. Each of the channels has a depth which reaches at least the above-mentioned major surface of the substrate. A first cladding layer covers the surface of the current blocking layer and those regions of the substrate which are exposed to the channels. A waveguide layer is deposited on the first cladding layer and has a surface opposite to the first cladding layer which is substantially flat. An active layer, a reflecting layer, a second cladding layer and a cap layer are deposited one upon another on the waveguide layer layer.