Abstract: An optical semiconductor device of the present invention is provided with a core layer having a quantum well layer in that film thickness gets thinner from a inner region to an end portion in an optical waveguide region.

Abstract: An optical semiconductor device of the present invention is provided with a core layer having a quantum well layer in that film thickness gets thinner from a inner region to an end portion in an optical waveguide region.

Abstract: A distribution feedback laser diode, comprises a substrate, a waveguide layer provided on the substrate, an active layer provided on the waveguide layer, a diffraction grating provided at an interface between the substrate and the waveguide layer for reflecting an optical radiation formed in the active layer back and forth, a clad layer provided on the active layer for confining the optical radiation within the active layer, a plurality of segmented electrodes provided on the top surface of the clad layer along an elongated direction of the laser diode for injecting the carriers into the active layer, wherein at least one of the segmented electrodes is provided in correspondence to a part of the active layer in which the optical radiation formed in the active layer has a maximum intensity level, and a backside electrode provided at the bottom surface of the substrate for injecting the carriers into the active layer through the substrate.

Abstract: An optical semiconductor device includes first and second cladding layers, a light guide layer sandwiched between the first and second cladding layers, and a layer structure provided in the light guide layer. The layer structure has a first periodic variation in a refractive index in a predetermined direction, and a second periodic variation in an optical gain in the predetermined direction. The first periodic variation has a period identical to that of the second periodic variation. The first periodic variation and the second periodic variation have a phase difference.

Abstract: A driver circuit of a laser diode. The laser diode has a first electrode structure for injecting a first drive current with a first magnitude and a second electrode structure separated from the first electrode structure for injecting a second drive current with a second magnitude. The second electrode structure is provided in correspondence to a location in diode at which said carriers are depleted most. The driver circuit comprises a presetting circuit for presetting a relationship between the first and second magnitudes, and a current distribution circuit controlled by the presetting circuit for producing the first and second drive currents with respective magnitude satisfying the relationship that is preset by the presetting means.

Abstract: A distribution feedback laser diode comprises a substrate, a waveguide layer provided on the substrate, an active layer provided on the waveguide layer, a diffraction grating provided at an interface between the substrate and the waveguide layer for reflecting an optical radiation formed in the active layer back and forth, a clad layer provided on the active layer for confining the optical radiation within the active layer, and a plurality of segmented electrodes provided on the top surface of the clad layer along an elongated direction of the laser diode for injecting the carriers into the active layer in dependence upon a modulation signal. At least one of the segmented electrodes is provided in correspondence to a part of the active layer in which the optical radiation formed in the active layer has a maximum intensity level, thereby enabling selective injection of carriers at that part of the active layer.