An active layer of a quantum cascade laser includes an active layer includes a plurality of emission regions and a plurality of injection regions. Each emission region includes an injection barrier layer, and an light-emitting quantum well layer that has at least two well layers, and that emits infrared light by undergoing an intersubband transition. Each injection region includes an extraction barrier layer, and a relaxation quantum well layer that creates an energy level for relaxing the energy of carriers from the each emission region. One of adjacent two well layers in the light-emitting quantum well layer of the each emission region on the side of the extraction barrier layer is deeper than a second well layer on the side of the injection barrier layer. The each emission region and the injection region are alternately stacked.

A solid-state device, and use and formation thereof. The device includes a light emitter (102) that emits light with abeam propagation direction and includes an emitter epitaxial layer stack (940); a light routing medium (103) in optical communication with the light emitter; and a light detector (104) in optical communication with the light routing medium, which detects light emitted by the light emitter and includes a detector epitaxial stack (945). The light emitter and detector are monolithically formed on a semiconductor substrate. The emitter and detector epitaxial layer stacks include different pluralities of layers of a single epitaxial layer stack. The beam propagation direction is either in-plane with the single epitaxial layer stack and the light detector detects light out of plane with the single epitaxial layer stack, or out of plane with the single epitaxial layer stack and the light detector detects light in plane with the single epitaxial layer stack.

A simple optical layout for a grazing angle probe mount that allows coupling to a mid-infrared (MIR), laser-based spectrometer is provided. The assembly enables doing reflectance measurements at high incident angles. In the case of optically thin films and deposits on MIR reflective substrates, a double pass effect, accompanied by absorption by the chemicals or biological samples deposited in an Infrared Reflection-Absorption Infrared Spectroscopy (IRRAS) modality is achieved. The optical system includes a probe that allows the passage of MIR light through the same sampling area twice. Initially, the infrared beam produces a spot on the surface, and then the light is returned in back reflection to the sample surface producing a new little slightly larger spot onto the selfsame position.

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 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 method for tuning the frequency of THz radiation is provided. The method utilizes an apparatus comprising a spin injector, a tunnel junction coupled to the spin injector, and a ferromagnetic material coupled to the tunnel junction. The ferromagnetic material comprises a Magnon Gain Medium (MGM). The method comprises the step of applying a bias voltage to shift a Fermi level of the spin injector with respect to the Fermi level of the ferromagnetic material to initiate generation of non-equilibrium magnons by injecting minority electrons into the Magnon Gain Medium. The method further comprises the step of tuning a frequency of the generated THz radiation by changing the value of the bias voltage.

A method is for making a QCL having an InP spacer within a laser core, the QCL to provide a CW output in a high quality beam. The method may include selectively setting parameters for the QCL. The parameters may include a number of the InP spacer, a thickness for each InP spacer, a number of stages in the laser core, and a dopant concentration value in the laser core. The method may include forming the QCL based upon the parameters so that a figure of merit comprises a greatest value for a fundamental mode of operation for the QCL.

A QCL may include a substrate, an emitting facet, and semiconductor layers adjacent the substrate and defining an active region. The active region may have a longitudinal axis canted at an oblique angle to the emitting facet of the substrate. The QCL may include an optical grating being adjacent the active region and configured to emit one of a CW laser output or a pulsed laser output through the emitting facet of substrate.

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.

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.