The light emitting device includes a substrate, and a laminated structure provided to the substrate, and including a plurality of columnar parts, wherein the columnar part includes a first semiconductor layer, a second semiconductor layer different in conductivity type from the first semiconductor layer, and a light emitting layer disposed between the first semiconductor layer and the second semiconductor layer, the laminated structure includes a third semiconductor layer which is connected to an opposite side to the substrate of the second semiconductor layer, and is same in conductivity type as the second semiconductor layer, the second semiconductor layer is disposed between the light emitting layer and the third semiconductor layer, the third semiconductor layer is provided with a recessed part, an opening of the recessed part is provided to a surface at an opposite side to the substrate side of the third semiconductor layer, and a diametrical size in a bottom of the recessed part is smaller than a diametrical size in the opening of the recessed part.

A QCL may include a substrate, and a sequence of semiconductor epitaxial layers adjacent the substrate and defining an active region, an injector region adjacent the active region, and a waveguide optically coupled to the active region. The active region may include stages, each stage having an upper laser level and a lower laser level defining respective first and second wave functions. The upper laser level may have an upper laser level average coordinate, and the lower laser level may have a lower laser level average coordinate. The upper laser level average coordinate and the lower laser level average coordinate may have spacing of less than 10 nm. Wave functions for all active region energy levels located below the lower laser level may have greater than 10% overlap with the injector region.

A semiconductor structure can include a substrate comprising a first in-plane lattice constant, a graded layer on the substrate, and a first region of the graded layer comprising a first epitaxial oxide material comprising a second in-plane lattice constant. The graded layer on the substrate can include (Al.sub.x1Ga.sub.1−x1).sub.y1O.sub.z1, wherein x1 is from 0 to 1, wherein y1 is from 1 to 3, wherein z1 is from 2 to 4, and wherein x1 varies in a growth direction such that the graded layer has the first in-plane lattice constant adjacent to the substrate and a second in-plane lattice constant at a surface of the graded layer opposite the substrate. In some cases, a semiconductor structure includes a first region comprising a first epitaxial oxide material; a second region comprising a second epitaxial oxide material; and the graded region located between the first and the second regions.

A plasmonic laser array device may comprise a first microcavity element having a first radiating end facet and a second radiating end facet opposite the first radiating end facet in a longitudinal direction of the device. The device may comprise a second microcavity element having a third radiating end facet and a fourth radiating end facet opposite the third radiating facet in the longitudinal direction. The device may comprise a first microcavity gap configured to separate the first microcavity element and the second microcavity element in the longitudinal direction. The device may comprise a bottom (e.g., metal) layer configured to underly the first microcavity element, the second microcavity element, and the first microcavity gap. The device may comprise an arrangement that places the first microcavity element and the second microcavity element into a phase-locked orientation for a phased-locked operation of the plasmonic laser array device.

A semiconductor laser includes: a multi-quantum well layer in a mesa structure; a buried layer comprising a semi-insulating semiconductor, the buried layer being in contact with each of both sides of the mesa structure; a first cladding layer with a first conductivity type, the first cladding layer having a lower refractive index than the multi-quantum well layer; a high refractive index layer configured to not absorb light oscillating in the multi-quantum well layer, the high refractive index layer having a higher refractive index than the first cladding layer; a diffraction grating layer at least partially constituting a diffraction grating capable of diffracting the light oscillating in the multi-quantum well layer, the diffraction grating layer not contacting the high refractive index layer; a substrate with the first conductivity type; and a second cladding layer with a second conductivity type above the multi-quantum well layer.

An optical apparatus comprises a semiconductor substrate, and a supermode filtering waveguide (SFW) emitter disposed on the semiconductor substrate. The SFW emitter comprises a first optical waveguide, a spacer layer, and a second optical waveguide spaced apart from the first optical waveguide by the spacer layer. The second optical waveguide is evanescently coupled with the first optical waveguide and is configured, in conjunction with the first waveguide, to selectively propagate only a first mode of a plurality of optical modes. The SFW emitter further comprises an optically active region disposed in one of the first optical waveguide and the second optical waveguide.

An optical apparatus comprises a semiconductor substrate, and a supermode filtering waveguide (SFW) emitter disposed on the semiconductor substrate. The SFW emitter comprises a first optical waveguide, a spacer layer, and a second optical waveguide spaced apart from the first optical waveguide by the spacer layer. The second optical waveguide is evanescently coupled with the first optical waveguide and is configured, in conjunction with the first waveguide, to selectively propagate only a first mode of a plurality of optical modes. The SFW emitter further comprises an optically active region disposed in one of the first optical waveguide and the second optical waveguide.

Building blocks are provided for on-chip chemical sensors and other highly-compact photonic integrated circuits combining interband or quantum cascade lasers and detectors with passive waveguides and other components integrated on a III-V or silicon. A MWIR or LWIR laser source is evanescently coupled into a passive extended or resonant-cavity waveguide that provides evanescent coupling to a sample gas (or liquid) for spectroscopic chemical sensing. In the case of an ICL, the uppermost layer of this passive waveguide has a relatively high index of refraction that enables it to form the core of the waveguide, while the ambient air, consisting of the sample gas, functions as the top cladding layer. A fraction of the propagating light beam is absorbed by the sample gas if it contains a chemical species having a fingerprint absorption feature within the spectral linewidth of the laser emission.

A quantum cascade laser device includes a QCL element; a lens; and a lens holder having a small-diameter hole, a large-diameter hole, and a counterbore surface. At least a part of a side surface of the lens is fixed to an inner surface of the large-diameter hole in a state where an edge portion of an incident surface of the lens is in contact with the counterbore surface. A central axis of the small-diameter hole is eccentric from that of the large-diameter hole. The side surface of the lens is positioned with respect to the inner surface of the large-diameter hole along a direction from the central axis of the large-diameter hole toward the central axis of the small-diameter hole. A central axis of the lens is disposed at a position closer to the central axis of the small-diameter hole than to the central axis of the large-diameter hole.

A light emitting device includes a substrate, a laminated structure provided to the substrate, and including a plurality of columnar parts, and a covering part configured to cover the laminated structure, wherein the columnar parts have a light emitting layer, and the covering part is provided with a through hole penetrating the covering part.