A semiconductor laser device includes an N-type cladding layer, an active layer, and a P-type cladding layer. The active layer includes a well layer, a P-side first barrier layer above the well layer, and a P-side second barrier layer above the P-side first barrier layer. The P-side second barrier layer has an AI composition ratio higher than an AI composition ratio of the P-side first barrier layer. The P-side second barrier layer has band gap energy greater than band gap energy of the P-side first barrier layer. The semiconductor laser device has an end face window structure in which band gap energy of a portion of the well layer in a vicinity of an end face that emits the laser light is greater than band gap energy of a central portion of the well layer in a resonator length direction.

A semiconductor optical device includes an active layer, the active layer including a plurality of quantum well layers having gain peak wavelengths different from one another in a layering direction thereof, and a plurality of barrier layers, wherein the quantum well layers and the barrier layers are alternately layered over each other, and an n-type dopant has been added in the plurality of quantum well layers having gain peak wavelengths different from one another and in the plurality of barrier layers.

A laser diode chip is described. In an embodiment the laser diode chip includes an n-type semiconductor region, a p-type semiconductor region and an active layer arranged between the n-type semiconductor region and the p-type semiconductor region, wherein the active layer is in the form of a single quantum well structure. The single quantum well structure includes a quantum well layer, which is arranged between a first barrier layer and a second barrier layer, wherein the first barrier layer faces the n-type semiconductor region, and the second barrier layer faces the p-type semiconductor region. An electronic bandgap E.sub.QW of the quantum well layer is smaller than an electronic bandgap E.sub.B1 of the first barrier layer and smaller than an electronic bandgap E.sub.B2 of the second barrier layer, and the electronic bandgap E.sub.B1 of the first barrier layer is larger than the electronic bandgap E.sub.B2 of the second barrier layer.

Disclosed is a semiconductor laser device assembly including a semiconductor laser device; and a dispersion compensation optical system, where a laser light exited from the semiconductor laser device is incident and exits to control a group velocity dispersion value of the laser light exited from the semiconductor laser device per wavelength.

A modulation doped semiconductor laser includes a multiple quantum well composed of a plurality of layers including a plurality of first layers and a plurality of second layers stacked alternately and including an acceptor and a donor; a p-type semiconductor layer in contact with an uppermost layer of the plurality of layers; and an n-type semiconductor layer in contact with a lowermost layer of the plurality of layers, the plurality of first layers including the acceptor so that a p-type carrier concentration is 10% or more and 150% or less of the p-type semiconductor layer, the plurality of second layers containing the acceptor so that the p-type carrier concentration is 10% or more and 150% or less of the p-type semiconductor layer, the plurality of second layers containing the donor, and an effective carrier concentration corresponding to a difference between the p-type carrier concentration and an n-type carrier concentration is 10% or less of the p-type carrier concentration of the plurality of second layers.

A gain medium for semiconductor optical amplifier in high-power operation includes a substrate with n-type doping; a lower clad layer formed overlying the substrate; a lower optical confinement stack overlying the lower clad layer; an active layer comprising a multi-quantum-well heterostructure with multiple well layers characterized by about 0.8% to 1.2% compressive strain respectively separated by multiple barrier layers characterized by about −0.1% to −0.5% tensile strain. The active layer overlays the lower optical confinement stack. The gain medium further includes an upper optical confinement stack overlying the active layer, the upper optical confinement stack being set thinner than the lower optical confinement stack; an upper clad layer overlying the upper optical confinement stack; and a p-type contact layer overlying the upper clad layer.

Surface-emitting laser devices and light-emitting devices including the same are provided. A surface-emitting laser device can include: a first reflective layer and a second reflective layer; and an active region disposed between the first reflective layer and the second reflective layer, wherein the first reflective layer includes a first group first reflective layer and a second group first reflective layer, and the second reflective layer includes a first group second reflective layer and a second group second reflective layer.

A monolithic laser device assembly 10A in the present disclosure includes a first gain portion 20 having a first end portion 20A and a second end portion 20B, a second gain portion 30 having a third end portion 30A and a fourth end portion 30B, one or multiple ring resonators 40, a semiconductor optical amplifier 50 for amplifying a laser light emitted from the first gain portion 20, and a pulse selector 60 disposed between the first gain portion 20 and the semiconductor optical amplifier 50, in which the ring resonator 40 is optically coupled with the first gain portion 20 and with the second gain portion 30, and laser oscillation is performed on either the first gain portion 20 or the second gain portion 30.

A quantum cascade laser device includes a semiconductor substrate, an active layer provided on the semiconductor substrate, and an upper clad layer provided on a side of the active layer opposite to the semiconductor substrate side and having a doping concentration of impurities of less than 1×10.sup.17 cm.sup.−3. Unit laminates included in the active layer each include a first emission upper level, a second emission upper level, and at least one emission lower level in their subband level structure. The active layer is configured to generate light having a center wavelength of 10 μm or more due to electron transition between at least two levels of the first emission upper level, the second emission upper level, and the at least one emission lower level in the light emission layer in each of the unit laminates.

A semiconductor light source is disclosed. In one embodiment, a semiconductor light source includes at least one semiconductor laser configured to generate a primary radiation and at least one conversion element configured to generate a longer-wave visible secondary radiation from the primary radiation, wherein the conversion element includes a semiconductor layer sequence having one or more quantum well layers, wherein, in operation, the primary radiation is irradiated into the semiconductor layer sequence parallel to a growth direction thereof, with a tolerance of at most 15°, wherein, in operation, the semiconductor layer sequence is homogeneously illuminated with the primary radiation, and wherein a growth substrate of the semiconductor layer sequence is located between the semiconductor layer sequence and the semiconductor laser, the growth substrate being oriented perpendicular to the growth direction.