Abstract: In a semiconductor device, a quantum dot group includes a stack of plural quantum dot layers having different central wavelengths at which respective gains are maximum. A part of or all of the quantum dot layers are stacked so that the central wavelengths sequentially shifts along a stacking direction. The quantum dot group includes a longest wavelength layer group composed of some quantum dot layers including a longest wavelength layer having a longest central wavelength and at least one quantum dot layer stacked on the longest wavelength layer. The longest wavelength layer or the longest wavelength layer group has a larger gain at the central wavelength than the gain at the central wavelength of each of the other quantum dot layers.

Abstract: The semiconductor laser device includes: an activation layer having at least one first quantum dot layer and at least one second quantum dot layer having a longer emission wavelength than the first quantum dot layer. The gain spectrum of the active layer has the maximum values at the first wavelength and the second wavelength longer than the first wavelength corresponding to the emission wavelength of the first quantum dot layer and the emission wavelength of the second quantum dot layer, respectively. The maximum value of the gain spectrum at the first wavelength is defined as the first maximum value, and the maximum value of the gain spectrum at the second wavelength is defined as the second maximum value. The first maximum value is larger than the second maximum value.

Abstract: An optical semiconductor device includes an active layer having a plurality of quantum dot layers. The plurality of quantum dot layers include: a first quantum dot layer doped with a p-type impurity; and a second quantum dot layer doped with an n-type impurity and having an emission wavelength different from that of the first quantum dot layer.

Abstract: An optical semiconductor device includes an active layer having a plurality of quantum dot layers. The plurality of quantum dot layers includes at least one quantum dot player doped with a p-type impurity. Further, the plurality of quantum dot layers includes at least two quantum dot layers having different emission wavelengths and different p-type impurity concentrations.

Abstract: The semiconductor laser device includes: an activation layer having at least one first quantum dot layer and at least one second quantum dot layer having a longer emission wavelength than the first quantum dot layer. The gain spectrum of the active layer has the maximum values at the first wavelength and the second wavelength longer than the first wavelength corresponding to the emission wavelength of the first quantum dot layer and the emission wavelength of the second quantum dot layer, respectively. The maximum value of the gain spectrum at the first wavelength is defined as the first maximum value, and the maximum value of the gain spectrum at the second wavelength is defined as the second maximum value. The first maximum value is larger than the second maximum value.

Abstract: A semiconductor light-emitting element includes: a lower clad layer 12 that is provided on a substrate 10; an active layer 20 that is provided on the lower clad layer 12 and includes a quantum well layer 24 and a plurality of quantum dots 28 sandwiching a second barrier layer 22b together with the quantum well layer 24; and an upper clad layer 14 that is provided on the active layer 20, wherein a distance D between the quantum well layer 24 and the plurality of quantum dots 28 is smaller than an average of distances X between centers of the plurality of quantum dots 28.

Abstract: A semiconductor light-emitting element includes: a lower clad layer 12 that is provided on a substrate 10; an active layer 20 that is provided on the lower clad layer 12 and includes a quantum well layer 24 and a plurality of quantum dots 28 sandwiching a second barrier layer 22b together with the quantum well layer 24; and an upper clad layer 14 that is provided on the active layer 20, wherein a distance D between the quantum well layer 24 and the plurality of quantum dots 28 is smaller than an average of distances X between centers of the plurality of quantum dots 28.

Abstract: A semiconductor optical communication module includes a semiconductor chip mounted on a chip carrier and a lens assembly having an end parallel to and facing the front edge of the chip carrier. The semiconductor chip has a front facet oriented at an acute angle to the front edge of the chip carrier. An optical waveguide in the semiconductor chip transmits an optical signal that propagates on an optical axis extending from the front facet of the semiconductor chip to the end of the lens assembly. The optical axis is orthogonal to the end of the lens assembly and the front edge of the chip carrier. The angled mounting of the semiconductor chip on the chip carrier allows the lens assembly to be placed close to the edge of the chip carrier, and to be moved for optical axis adjustment without striking the chip carrier.

Abstract: A laser diode chip (110) is placed in the vicinity of the center of a sub-mount (120) under the condition that the distance (b) between an edge on an output side of the sub-mount (120) and the front face of the laser diode chip (110) meets the formula, (b)<(a)/tan(&thgr;/2), wherein the (a) is the distance between the upper surface of the sub-mount (120) and the lower surface of an active layer (140) of the laser diode chip (110) and the &thgr; is the angle of the spread in the vertical direction of the laser beam emitted from the active layer (140).

Abstract: A mask layer is formed on a semiconductor substrate such that an elongate opening of the mask layer extends lengthwise at an angle relative to a [011] direction of the semiconductor substrate. A ridge waveguide structure including an active layer is formed within the elongate opening on the semiconductor substrate by a selective growth method using the mask layer as a mask. The mask layer is then removed, and a clad layer is formed over the ridge waveguide structure.

Abstract: A method of fabricating a semiconductor laser diode includes forming a mask layer on a semiconductor substrate and forming a ridge waveguide structure including an active layer on the semiconductor substrate by selective growth method using the mask layer. The mask layer is formed to be along a direction with an angle to [011] direction of the semiconductor substrate.