Abstract: The present invention provides a QCL device with an electrically controlled refractive index through the Stark effect. By changing the electric field in the active area, the energy spacing between the lasing energy levels may be changed and, hence, the effective refractive index in the spectral region near the laser wavelength may be controlled.

Abstract: A semiconductor light source comprises a substrate, lower and upper claddings, a waveguide region with imbedded active area, and electrical contacts to provide voltage necessary for the wavelength tuning. The active region includes single or several heterojunction periods sandwiched between charge accumulation layers. Each of the active region periods comprises higher and lower affinity semiconductor layers with type-II band alignment. The charge carrier accumulation in the charge accumulation layers results in electric field build-up and leads to the formation of generally triangular electron and hole potential wells in the higher and lower affinity layers. Nonequillibrium carriers can be created in the active region by means of electrical injection or optical pumping. The ground state energy in the triangular wells and the radiation wavelength can be tuned by changing the voltage drop across the active region.

Abstract: Quantum-cascade lasers are provided with an active section in which relaxation of carriers from a lower laser level is provided by three or more phonon-assisted transitions to levels within the active section whose energies are below the energy of the lower laser level. The gain region of the laser consists of alternating active and injector sections, with an injection barrier inserted between each injector section and the adjacent active section, and an exit barrier inserted between each active section and the adjacent injector section. The active section comprises a sufficient number of quantum wells separated by quantum barriers to produce the desired energy-level structure consisting of an upper laser level, a lower laser level, and at least three levels that have lower energies than the lower laser level, with the separation of adjacent energy levels below and including the lower laser level that are at least equal to the energy of the quantum well material's longitudinal optical phonon.

Abstract: Electrically conductive, embedded current injection layers are provided in combination with cladding layers to provided improved current conduction to the active light-emitting regions of semiconductor light-emitting devices. The embedded electrical contact layers are used to inject current directly into the active region of semiconductor light-emitting devices. Free-carrier loss within the cladding layers is reduced, and power efficiency is improved by eliminating voltage drops associated with current transport through the cladding layers. Moreover, use of the embedded current injection layers eliminates the need to transport current through the cladding layers thereby allowing the use of a wider range of materials for the cladding layers. The present current injection layers may be embedded in various semiconductor light-emitting devices, i.e.

Abstract: Cladding layers for semiconductor lasers provide improved heat transfer and optical confinement properties. The cladding layers may comprise superlattices such as AlSb/GaAs, AlSb/AlAs, AlSb/GaSb/AlAs, AlGaSb/AlGaAs and AlSb/AlGaAs. The cladding layers may also comprise Al-As-Sb ternary alloys or Al-Ga-As-Sb quaternary alloys. Such cladding layers may be used in interband cascade lasers or other types of semiconductor lasers to significantly increase heat flow out of the active light-emitting region of the device, while providing improved optical confinement characteristics.

Abstract: The present invention relates to quantum well semiconductor light emitting devices such as lasers and other devices that utilize type-II quantum wells and interband transitions of energy states between the conduction band and the valence band for light emission, resulting in significant improvement in radiative efficiency. The semiconductor light emitting devices comprise a multilayer semiconductor structure comprising a plurality of essentially identical active regions, each active region being separated from its adjoining active regions by an injection region that serves as the collector for the preceding active region and the emitter for the following active region. Each of said active regions comprises multiple quantum well regions or finite superlattice regions to improve carrier injection efficiency and enhance optical gain without using a large number of cascade stages. This can reduce the operating voltage and increase the power efficiency.