Abstract: A vertical optical modulator comprising: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type bonded to the first semiconductor layer; a third semiconductor layer of the second conductivity type; a dielectric layer formed between the second semiconductor layer and the third semiconductor layer; an antenna electrode having a plurality of conductive pieces which are formed within the dielectric layer so as to have a net-like shape as a whole, to be separated from one another at the intersections of the net-like shape, and to be in contact with both the second semiconductor layer and the third semiconductor layer; a first electrode electrically connected to the first semiconductor layer; and a second electrode electrically connected to the third semiconductor layer.

Abstract: A vertical optical modulator comprising: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type bonded to the first semiconductor layer; a third semiconductor layer of the second conductivity type; a dielectric layer formed between the second semiconductor layer and the third semiconductor layer; an antenna electrode having a plurality of conductive pieces which are formed within the dielectric layer so as to have a net-like shape as a whole, to be separated from one another at the intersections of the net-like shape, and to be in contact with both the second semiconductor layer and the third semiconductor layer; a first electrode electrically connected to the first semiconductor layer; and a second electrode electrically connected to the third semiconductor layer

Abstract: A vertical optical modulator comprising: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type bonded to the first semiconductor layer; a third semiconductor layer of the second conductivity type; a dielectric layer formed between the second semiconductor layer and the third semiconductor layer; an antenna electrode having a plurality of conductive pieces which are formed within the dielectric layer so as to have a net-like shape as a whole, to be separated from one another at the intersections of the net-like shape, and to be in contact with both the second semiconductor layer and the third semiconductor layer; a first electrode electrically connected to the first semiconductor layer; and a second electrode electrically connected to the third semiconductor layer.

Abstract: A vertical optical modulator comprising: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type bonded to the first semiconductor layer; a third semiconductor layer of the second conductivity type; a dielectric layer formed between the second semiconductor layer and the third semiconductor layer; an antenna electrode having a plurality of conductive pieces which are formed within the dielectric layer so as to have a net-like shape as a whole, to be separated from one another at the intersections of the net-like shape, and to be in contact with both the second semiconductor layer and the third semiconductor layer; a first electrode electrically connected to the first semiconductor layer; and a second electrode electrically connected to the third semiconductor layer.

Abstract: The semiconductor laser device of the present invention includes a GaAs substrate and a multi-layer structure formed on the GaAs substrate. The multi-layer structure includes an active layer for emitting light. The active layer includes an InNxAsyP1−x−y (where 0<x<1 and 0≦y<1) layer that is lattice-matched with the GaAs substrate.

Abstract: The semiconductor laser of the invention includes: a semiconductor substrate of a first conductivity type; a stripe-shaped multilayer structure, formed on the semiconductor substrate, the stripe-shaped multilayer structure including an active layer; and a current blocking portion formed on the semiconductor substrate on both sides of the stripe-shaped multilayer structure, wherein the current blocking portion has a first current blocking layer of a second conductivity type, and a second current blocking layer of the first conductivity type formed on the first current blocking layer, the first current blocking layer includes a low-concentration region having a relatively low concentration of an impurity of the second conductivity type, and a high-concentration region having an impurity concentration which is higher than that of the low-concentration region, and the low-concentration region is provided at a position closer to the stripe-shaped multilayer structure than the high-concentration region.

Abstract: In a semiconductor laser device 100, an n-type InGaAsP light confinement layer 2, a multiple quantum well active layer 3, a p-type InGaAsP light confinement layer 4, and a p-type InP cladding layer 5 are formed on an n-type InP substrate 1 to be in a mesa structure extending in stripes along the cavity length direction. Moreover, regions on both sides of this striped mesa are buried with a p-type InP current blocking layer 6 and an n-type InP current blocking layer 7. Furthermore, a p-type InP burying layer 8 and a p-type InGaAsP contact layer 9 are formed thereon. The oscillation wavelength of the semiconductor laser device 100 is around 1.3 .mu.m. The stripe width of the active layer 3 is such that the width W1 at the front end face and the width W2 at the rear end face have a relationship of W1<W2, and the stripe width is continuously reduced from W2 to W1 along the cavity length direction.

Abstract: A distributed feedback semiconductor laser which includes a semiconductor substrate of a first conductive type; a semiconductor multi-layer structure provided on the semiconductor substrate and including an active layer for generating laser light; and a gain-coupled diffraction grating provided between the semiconductor substrate and the semiconductor multi-layer structure. The diffraction grating includes a plurality of curved projections periodically arranged at a surface of the semiconductor substrate and a quantum well light absorption layer for covering the plurality of curved projections. The quantum well light absorption layer includes a light absorption area having a first thickness at each border between two adjacent curved projections and a non-light absorption area having a second thickness which is smaller than the first thickness at a top of each of the curved projections.

Abstract: The semiconductor laser of the invention includes: a semiconductor substrate of a first conductivity type; a stripe-shaped multilayer structure, formed on the semiconductor substrate, the stripe-shaped multilayer structure including an active layer; and a current blocking portion formed on the semiconductor substrate on both sides of the stripe-shaped multilayer structure, wherein the current blocking portion has a first current blocking layer of a second conductivity type, and a second current blocking layer of the first conductivity type formed on the first current blocking layer, the first current blocking layer includes a low-concentration region having a relatively low concentration of an impurity of the second conductivity type, and a high-concentration region having an impurity concentration which is higher than that of the low-concentration region, and the low-concentration region is provided at a position closer to the stripe-shaped multilayer structure than the high-concentration region.

Abstract: A distributed feedback semiconductor laser which includes a semiconductor substrate of a first conductive type; a semiconductor multi-layer structure provided on the semiconductor substrate and including an active layer for generating laser light; and a gain-coupled diffraction grating provided between the semiconductor substrate and the semiconductor multi-layer structure. The diffraction grating includes a plurality of curved projections periodically arranged at a surface of the semiconductor substrate and a quantum well light absorption layer for covering the plurality of curved projections. The quantum well light absorption layer includes a light absorption area having a first thickness at each border between two adjacent curved projections and a non-light absorption area having a second thickness which is smaller than the first thickness at a top of each of the curved projections.

Abstract: A multi quantum well semiconductor laser includes an InP substrate and a multi-layered structure formed on the InP substrate, lasing at 1.29 .mu.m to 1.33 .mu.m wavelength, wherein the multi-layered structure includes at least a multi quantum well active layer, the multi quantum well active layer including InGaAsP well layers and InGaAsP barrier layers alternately provided, the InGaAsP barrier layers are lattice matched with the InP substrate, and a bandgap wavelength of the InGaAsP barrier layers is substantially equal to 1.05 .mu.m.

Abstract: The semiconductor laser of the invention includes: a semiconductor substrate of a first conductivity type; a stripe-shaped multilayer structure, formed on the semiconductor substrate, the stripe-shaped multilayer structure including an active layer; and a current blocking portion formed on the semiconductor substrate on both sides of the stripe-shaped multilayer structure, wherein the current blocking portion has a first current blocking layer of a second conductivity type, and a second current blocking layer of the first conductivity type formed on the first current blocking layer, the first current blocking layer includes a low-concentration region having a relatively low concentration of an impurity of the second conductivity type, and a high-concentration region having an impurity concentration which is higher than that of the low-concentration region, and the low-concentration region is provided at a position closer to the stripe-shaped multilayer structure than the high-concentration region.

Abstract: A distributed feedback semiconductor laser which includes a semiconductor substrate of a first conductive type; a semiconductor multi-layer structure provided on the semiconductor substrate and including an active layer for generating laser light; and a gain-coupled diffraction grating provided between the semiconductor substrate and the semiconductor multi-layer structure. The diffraction grating includes a plurality of curved projections periodically arranged at a surface of the semiconductor substrate and a quantum well light absorption layer for covering the plurality of curved projections. The quantum well light absorption layer includes a light absorption area having a first thickness at each border between two adjacent curved projections and a non-light absorption area having a second thickness which is smaller than the first thickness at a top of each of the curved projections.