Abstract: An optical semiconductor device includes a semiconductor multilayer structure, an active region interposed between a first facet on a light emitting side and a second facet opposing to the first facet, and a first electrode layer provided on a top of the semiconductor multilayer structure and a second electrode layer provided on a bottom of the semiconductor multilayer structure; and an electrical connection region connected to at least one of the first electrode layer and the second electrode layer of the optical semiconductor device and used for injecting a current to the active region, and ?>? and ?>0 are satisfied where ? is the contact area included in a half region on the first facet side in a top area of the optical semiconductor device and ? is the contact area included in a half region on the second facet side.

Abstract: A submount on which a semiconductor device is mounted and which is mounted on a base made of metal, the submount including: a substrate; a first coating layer formed on a first surface of the substrate and made of a material having a higher coefficient of thermal expansion than that of the substrate; and a second coating layer formed on a second surface, positioned on a side opposite to the first surface, of the substrate and made of a material having a higher coefficient of thermal expansion than that of the substrate, in which a coating area of the second coating layer is smaller than a coating area of the first coating layer.

Abstract: An optical semiconductor device includes a semiconductor multilayer structure, an active region interposed between a first facet on a light emitting side and a second facet opposing to the first facet, and a first electrode layer provided on a top of the semiconductor multilayer structure and a second electrode layer provided on a bottom of the semiconductor multilayer structure; and an electrical connection region connected to at least one of the first electrode layer and the second electrode layer of the optical semiconductor device and used for injecting a current to the active region, and ?>? and ?>0 are satisfied where ? is the contact area included in a half region on the first facet side in a top area of the optical semiconductor device and ? is the contact area included in a half region on the second facet side.

Abstract: A semiconductor laser device includes a semiconductor layer portion having an active layer and performs multi-mode oscillation of laser light. Further, the semiconductor layer portion includes first and second regions, the second region being located closer to a facet on a laser light radiation side than the first region, the first region and the second region include a stripe region in which the laser light is guided, and an optical confinement effect of the laser light to the stripe region in a horizontal direction in the second region is less than that in the first region.

Abstract: A submount on which a semiconductor device is mounted and which is mounted on a base made of metal, the submount including: a substrate; a first coating layer formed on a first surface of the substrate and made of a material having a higher coefficient of thermal expansion than that of the substrate; and a second coating layer formed on a second surface, positioned on a side opposite to the first surface, of the substrate and made of a material having a higher coefficient of thermal expansion than that of the substrate, in which a coating area of the second coating layer is smaller than a coating area of the first coating layer.

Abstract: A semiconductor laser device includes a semiconductor layer portion having an active layer and performs multi-mode oscillation of laser light. Further, the semiconductor layer portion includes first and second regions, the second region being located closer to a facet on a laser light radiation side than the first region, the first region and the second region include a stripe region in which the laser light is guided, and an optical confinement effect of the laser light to the stripe region in a horizontal direction in the second region is less than that in the first region.

Abstract: A semiconductor laser device with an active layer having a multi-quantum well structure including more than one well layer and more than one barrier layer and having a cavity length of more than 800 ?m is disclosed, wherein the active layer includes a doped region which includes at least one well layer and at least one barrier layer adjacent to the well layer. The entire active region, comprising all of the well and active layers may be doped. Adjacent to the active layer are upper and lower optical confinement layers falls having a thickness within a range of from about 20 to about 50 nm. A optical fiber amplifier incorporating the semiconductor laser is also disclosed, including the semiconductor laser device sealed within a package disposed over a cooler, and wherein a light incidence facet of an optical fiber is optically coupled to the optical output power facet of the semiconductor laser device.

Abstract: A semiconductor laser device is provided in which compositions of a lower optical confinement layer and an upper optical confinement layer are continuously changed in a thickness direction and the change in composition is reverse with respect to an active layer.

Abstract: A semiconductor laser device is provided in which compositions of a lower optical confinement layer and an upper optical confinement layer are continuously changed in a thickness direction and the change in composition is reverse with respect to an active layer.

Abstract: A semiconductor laser device with an active layer having a multi-quantum well structure including more than one well layer and more than one barrier layer and having a cavity length of more than 800 &mgr;m is disclosed, wherein the active layer includes a doped region which includes at least one well layer and at least one barrier layer adjacent to the well layer. The entire active region, comprising all of the well and active layers may be doped. Adjacent to the active layer are upper and lower optical confinement layers falls having a thickness within a range of from about 20 to about 50 nm. A optical fiber amplifier incorporating the semiconductor laser is also disclosed, including the semiconductor laser device sealed within a package disposed over a cooler, and wherein a light incidence facet of an optical fiber is optically coupled to the optical output power facet of the semiconductor laser device.