In an embodiment, a laser includes a gain section. The gain section includes an active region, an upper separate confinement heterostructure (SCH), and a lower SCH. The upper SCH is above the active region and has a thickness of at least 60 nanometers (nm). The lower SCH is below the active region and has a thickness of at least 60 nm.

A gas measuring apparatus includes a cell portion, a light source portion, a detection portion, and a control portion. The cell portion includes a space into which a sample gas containing breath containing a first isotope of carbon dioxide and a second isotope of carbon dioxide is introduced. The light source portion changes a wavelength of the light in a band of 4.345 μm or more and 4.384 μm or less. The detection portion performs an operation including first detection of an intensity of the light passing through the space and second detection of an intensity of the light passing through the space into which the sample gas is not introduced. The control portion calculates a ratio of an amount of the second isotope to an amount of the first isotope based on a result of the first detection and a result of the second detection.

A strained quantum well structure of the present disclosure is a type I strained quantum well structure grown by using an InP crystal as a substrate and including a luminescence wavelength of 1.9 μm or longer and 2.5 μm or shorter, in which a well layer is an InGaAs, InAs, or InGaAsSb crystal including a compression strain, a barrier layer is an InGaAsSb crystal including a tensile strain, and a band discontinuity in a conduction band is 100 meV or greater.

A vertical-cavity surface-emitting laser (VCSEL) including a substrate including a plurality of emitters forming an array region, a lower mirror, an upper mirror, an active layer interposed between the lower mirror and the upper mirror, an aperture forming layer interposed between the upper mirror and the active layer and including an oxidation region and a window region, a connector disposed on the upper mirror, a plurality of oxidation holes passing through the upper mirror and the aperture forming layer, an upper insulation layer covering the plurality of oxidation holes, and a pad electrically connected to the connector, in which at least a portion of the connector is disposed in the plurality of oxidation holes, the plurality of emitters is disposed in substantially a honeycomb shape on the substrate, and the pad is formed on one side of the substrate adjacent to the array region.

This semiconductor laser device includes a semiconductor laser chip and a spatial light modulator SLM optically coupled to the semiconductor laser chip. The semiconductor laser chip LDC includes an active layer 4, a pair of cladding layers 2 and 7 sandwiching the active layer 4, a diffraction grating layer 6 optically coupled to the active layer 4, and a drive electrode E3 that is disposed between the cladding layer 2 and the spatial light modulator SLM and supplies an electric current to the active layer 4, and the drive electrode E3 is positioned within an XY plane and has a plurality of openings as viewed from a Z-axis direction and has a non-periodic structure.

Methods of passivating at least one facet of a multilayer waveguide structure can include: cleaning, in a first chamber of a multi-chamber ultra-high vacuum (UHV) system, a first facet of the multilayer waveguide structure; transferring the cleaned multilayer waveguide structure from the first chamber to a second chamber of the multi-chamber UHV system; forming, in the second chamber, a first single crystalline passivation layer on the first facet; transferring the multilayer waveguide structure from the second chamber to a third chamber of the multi-chamber UHV system; and forming, in the third chamber, a first dielectric coating on the first single crystalline passivation layer, in which the methods are performed in an UHV environment of the multi-chamber UHV system without removing the multilayer waveguide structure from the UHV environment.

A quantum cascade laser includes a semiconductor substrate and an active layer having a cascade structure, in which unit layered bodies, each composed of a quantum well light emitting layer and an injection layer, are stacked, wherein the unit layered body has a subband level structure having an upper laser level, a lower laser level, and a relaxation miniband composed of at least two energy levels with an energy spacing smaller than the energy difference (E.sub.UL) between the upper laser level and the lower laser level, the energy width of the relaxation miniband is smaller than the energy (E.sub.LO−E.sub.UL) obtained by subtracting the energy difference (E.sub.UL) from the energy (E.sub.LO) of longitudinal optical phonons, and electrons subjected to the intersubband transition are relaxed in the relaxation miniband and are injected into a quantum well light emitting layer in a subsequent unit layered body.

A semiconductor stack includes a first-conductivity-type layer, a quantum well structure, and a second-conductivity-type layer. The first-conductivity-type layer, the quantum well structure, and the second-conductivity-type layer are stacked in this order. The quantum well structure includes a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer. In the first semiconductor layer and the third semiconductor layer, compositions of the first semiconductor layer and the third semiconductor layer are changed such that a bandgap decreases toward the second semiconductor layer. Transition of an electron is possible between a conduction band of each of the first semiconductor layer and the third semiconductor layer and a valence band of the second semiconductor layer.

A quantum cascade laser includes a substrate having a group III-V compound semiconductor and a core region that is provided on the substrate and that includes a group III-V compound semiconductor. The core region includes a plurality of unit structures that are stacked on top of one another. Each of the plurality of unit structures includes an active layer and an injection layer. The injection layer includes at least one strain-compensated layer including a first well layer and a first barrier layer and at least one lattice-matched layer including a second well layer and a second barrier layer. The first well layer has a lattice constant larger than a lattice constant of the substrate. The first barrier layer has a lattice constant smaller than the lattice constant of the substrate. The second well layer and the second barrier layer each have a lattice constant that is lattice-matched to the substrate.

The present disclosure describes broadband optical emission sources that include a stack of semiconductor layers, wherein each of the semiconductor layers is operable to emit light of a different respective wavelength; a light source operable to provide optical pumping for stimulated photon emission from the stack; wherein the semiconductor layers are disposed sequentially in the stack such that a first one of the semiconductor layers is closest to the light source and a last one of the semiconductor layers is furthest from the light source, and wherein each particular one of the semiconductor layers is at least partially transparent to the light generated by the other semiconductor layers that are closer to the light source than the particular semiconductor layer. The disclosure also describes various spectrometers that include a broadband optical emission device, and optionally include a tuneable wavelength filter operable to allow a selected wavelength or narrow range of wavelengths to pass through.