A semiconductor laser includes an active layer which is provided between the p-type semiconductor region and the n-type semiconductor region and has a type II quantum well structure. The type II quantum well structure includes a well layer made of a III-V compound semiconductor and a plurality of barrier layers. The well layer includes a first region and a second region, the first region having a low potential for electrons in the well layer and a high potential for holes in the well layer, the second region having a high potential for electrons in the well layer and a low potential for holes in the well layer. The first region and the second region of the well layer are arranged in a direction from one of the barrier layers to another of the barrier layers.

A method for tuning an emission wavelength of a laser device, including: acquiring a drive condition of a wavelength tunable laser diode to make the wavelength tunable laser diode oscillate at a wavelength from a memory; driving a first thermo-cooler and a first heater based on the drive condition of the wavelength tunable laser diode; determining whether respective control values of the first thermo-cooler and the first heater are reached within a first range of target values; and driving a gain region after the control values have been reached within the first range.

A semiconductor laser device includes a first semiconductor layer and an active layer provided above the first semiconductor layer. The first semiconductor layer is a superlattice layer and includes a plurality of first layers and a plurality of second layers. The plurality first layers and the plurality of second layers are alternately stacked upon each other. Thicknesses of the plurality of first layers are equal to each other, and thicknesses of the plurality of second layers are equal to each other.

[Object] To provide a laser device that has a concave mirror structure and exhibits excellent optical characteristics, a laser device array, and a method of producing the laser device.

[Solving Means] A laser device according to the present technology includes: a first light-reflecting layer; a second light-reflecting layer; and a stacked body. The stacked body includes an active layer, a lens being provided on a first surface on a side of the first light-reflecting layer. The lens has a lens shape protruding toward a side of the first light-reflecting layer with a first direction as a longitudinal direction and a second direction as a lateral direction, a central portion of the lens in the first direction having a first width that is the shortest width along the second direction, a non-central portion of the lens in the first direction having a second width that is the largest width along the second direction, the lens having a shape in which a height thereof is uniform or the central portion is higher than an end portion, a radius of curvature of an apex of the lens in the second direction being uniform. The first light-reflecting layer is stacked on the first surface to form a concave mirror having a concave surface shape on the lens.

An optical modulator is formed on a substrate constituted of InP, and an active layer is formed on the substrate via a lower InP layer constituted of InP. The active layer has a multiple quantum well structure including a well layer constituted of a group III-V compound semiconductor including In, As, and P as constituent elements and a barrier layer constituted of a group III-V compound semiconductor including In, Ga, P, and Sb as constituent elements.

A semiconductor nanolaser includes a rib formed by a stack of layers, in which stack central layers (33, 34, 35) forming an assembly of quantum wells are placed between a lower layer (32) of a first conductivity type and an upper layer (36) of a second conductivity type. Holes (42) are drilled right through the thickness of the rib, wherein the lower layer includes first extensions (38, 40) that extend laterally on either side of the rib, and that are coated with first metallizations (42, 44) that are located a distance away from the rib. The stack includes second extensions (45, 46) that extend longitudinally beyond said rib, and that are coated with second metallizations (47, 48).

A light emitting device includes: a first semiconductor light emitting element that includes a first active layer and a first resonator portion over a semiconductor substrate, and emits a first light; a second semiconductor light emitting element that includes a first reflector, a second resonator portion including a second active layer excited by the first light, and a second reflector stacked in this order over the first semiconductor light emitting element, and emits a second light, wherein an oscillation wavelength of the second semiconductor light emitting element is longer than that of the first semiconductor light emitting element, wherein the second semiconductor light emitting element includes a saturable absorption layer between the second resonator portion and the second reflector, and wherein a thickness L and an absorption coefficient ? of the second active layer satisfy the following inequality.

[00001]$3.45???L?15$

A semiconductor laser may include a substrate, a multi quantum well (MQW) active layer, and an electron stopper layer. The MQW active layer may include a quantum well that is tensile strained and a barrier that is compressively strained. The barrier may be formed from an aluminum gallium indium arsenide phosphide alloy having a first Al.sub.xGa.sub.yIn.sub.(1-x-y)As.sub.zP.sub.(1-z) composition. The electron stopper layer may include an aluminum gallium indium arsenide phosphide alloy having a second Al.sub.xGa.sub.yIn.sub.(1-x-y)As.sub.zP.sub.(1-z) composition.

A process of forming a semiconductor optical device is disclosed. The semiconductor optical device provides a waveguide structure accompanied with a heater for varying a temperature of the waveguide structure. The process includes steps of: (a) forming a striped mask on a semiconductor substrate; (b) selectively growing a dummy layer on the semiconductor substrate; (c) removing the patterned mask; (d) burying the dummy layer by a supplemental layer; (e) exposing a portion of the dummy layer by etching a portion of the supplemental layer; (f) and removing the dummy layer by immersing the dummy layer within a solution that shows an etching rate for the dummy layer enough faster than an etching rate for the supplemental layer and the substrate so as to leave a void in a region the dummy layer had existed.

A semiconductor nanolaser includes a rib formed by a stack of layers, in which stack central layers (33, 34, 35) forming an assembly of quantum wells are placed between a lower layer (32) of a first conductivity type and an upper layer (36) of a second conductivity type. Holes (42) are drilled right through the thickness of the rib, wherein the lower layer includes first extensions (38, 40) that extend laterally on either side of the rib, and that are coated with first metallizations (42, 44) that are located a distance away from the rib. The stack includes second extensions (45, 46) that extend longitudinally beyond said rib, and that are coated with second metallizations (47, 48).