Abstract: An optical gain medium has first and second active layers and an injector layer interposed between the first and second active layers. The active layers have upper minibands and lower minibands. The injector layer has a miniband that transports charge carriers from the lower miniband of the first active layer to an excited state in the upper miniband of the second active layer in response to application of a voltage across the optical gain medium.

Abstract: An intersubband (ISB) optical device comprises first quantum well (QW) interior regions having upper and lower energy states between which ISB transitions take place; and superlattice (SL) barrier regions interposed between the first QW interior regions. The SL barrier regions include second barriers and second QW interior regions, with the second QW interior regions being interposed between the second barrier regions. The first QW interior regions and the SL barrier regions are configured to produce an energy gap between the upper and lower states that is larger than the energy of a 1.7 &mgr;m wavelength photon. In accordance with another aspect of our invention, an intersubband optical device comprises a core region that includes a multiplicity of repeat units (RUs), each RU including a first barrier region and a QW active region disposed adjacent thereto, characterized in that (1) each of the QWs has upper and lower energy states separated by an energy greater than that of a 1.

Abstract: A process for optically transmitting data to a remote receiver includes receiving a stream of input data signals and modulating a mid-IR laser by direct modulation with a waveform whose sequential values are responsive of the data signals of the stream. The direct modulation includes pumping the mid-IR laser to produce high and low optical power levels in response to different ones of the values. The process also includes transmitting output light from the modulated mid-IR laser to the remote receiver via a free space communications channel.

Abstract: An article comprising a QC-DFB laser is disclosed. In the QC-DFB laser, an overlying grating structure achieves relatively strong coupling of the guided mode to the grating, and is thus highly effective in inducing single-mode operation even under cw operating conditions. The grating structure includes grooves etched in a plasmon-enhanced confinement layer (PECL) disposed adjacent and in contact with an upper metallic electrode. The grating structure and the PECL are designed such that in the grooves, the laser mode travelling in the waveguide can couple efficiently to the surface-plasmon at the electrode interface. This results in strong modulation of the laser mode, leading to strong modulation of, inter alia, the effective refractive index.

Abstract: A solid state laser comprises a cavity resonator in the form of a generally cylindrical body and, located within the resonator, an active region which generates lasing light when suitably pumped. The resonator has a relatively high effective refractive index (n>2 and typically n>3) is sufficiently deformed from circularity so as to support at least one librational mode (e.g., a V-shaped or a bow-tie mode, the latter being presently preferred for generating relatively high power, directional outputs). Specifically described is a Group III-V compound semiconductor, quantum cascade (QC), micro-cylinder laser in which the resonator has a flattened quadrupolar deformation from circularity. This laser exhibits both a highly directional output emission and a three-order of magnitude increase in optical output power compared to conventional semiconductor micro-cylinder QC lasers having circularly symmetric resonators.

Abstract: A mounting technology that increases the cw operating temperature of intersubband lasers, without increasing the risk of hot spots near the facets and short circuits near the perimeter of the laser chip, is described.

Abstract: An intersubband semiconductor light source comprises a core region that includes a unipolar, radiative transition (RT) region having upper and lower energy levels, an injector-only (I) region disposed on one side of the RT region, and a reflector/extractor-only (R/E) region disposed on the other side of the RT region. The I region has a first miniband of energy levels aligned so as to inject electrons into the upper energy level, and the R/E region has a second miniband of energy levels aligned so as to extract electrons from the lower energy level. The R/E region also has a minigap aligned so as to inhibit the extraction of electrons from the upper level. A suitable voltage applied across the core region is effective to cause the RT region to generate light at a wavelength determined by the energy difference between the upper and lower energy levels. Low voltage operation at less than 3 V is described.

Abstract: A long wavelength (e.g., mid-IR to far-IR) semiconductor laser comprises an active region and at least one cladding region characterized in that the cladding region includes a light guiding interface between two materials which have dielectric constants opposite in sign. Consequently, the guided modes are transverse magnetic polarized surface waves (i.e., surface plasmons) which propagate along the interface without the need for a traditional dielectric cladding. In a preferred embodiment, the interface is formed between a semiconductor layer and a metal layer. The complex refractive index of the metal layer preferably has an imaginary component which is much larger than its real component. In an illustrative embodiment, our laser includes a QC active region sandwiched between a pair of cladding regions one of which is a guiding interface based on surface plasmons and the other of which is a dielectric (e.g., semiconductor) structure.

Abstract: A bi-directional semiconductor light source is formed that provides emission in response to either a positive or negative bias voltage. In a preferred embodiment with an asymmetric injector region in a cascade structure, the device will emit at a first wavelength (&lgr;−) under a negative bias and a second wavelength (&lgr;+) under a positive bias. In other embodiments, the utilization of an asymmetric injector region can be used to provide a light source with two different power levels, or operating voltages, as a function of the bias polarity.

Abstract: Disclosed are a method of making GaAs-based enhancement-type MOS-FETs, and articles (e.g., GaAs-based ICs) that comprise such a MOS-FET. The MOS-FETs are planar devices, without etched recess or epitaxial re-growth, with gate oxide that is primarily Ga2O3, and with low midgap interface state density (e.g., at most 1×1011 cm−2 eV−1 at 20° C.). The method involves ion implantation, implant activation in an As-containing atmosphere, surface reconstruction, and in situ deposition of the gate oxide. In preferred embodiments, no processing step subsequent to gate oxide formation is carried out above 300° C. in air, or above about 700° C. in UHV. The method makes possible fabrication of planar enhancement-type MOS-FETs having excellent characteristics, and also makes possible fabrication of complementary MOS-FETs, as well as ICs comprising MOS-FETs and MES-FETs.

Abstract: A method of forming selected Group III-nitride regions uses a masking layer to cause differential growth between single crystal Group III-nitride material and polycrystalline Group III-nitride material. The epitaxial process is chosen to provide vertical growth so as to allow for replication of the mask edges at the defined limits for the selected regions. By using an etchant that is selective between polycrystalline and single crystal Group III-nitride material, the polycrystalline material (that grew over the mask layer) can be removed, leaving only the single crystal Group III-nitride (that grew over the exposed substrate material).

Abstract: An MQW laser comprises an active region in which a multiplicity of barriers each includes a doped barrier layer separated from its adjacent quantum well layers by undoped barrier layers. In a preferred embodiment, each barrier of an InGaAsP/InP SCH MQW laser includes a p-type (e.g., Be, Mg or C) delta-doped InGaAsP barrier layer sandwiched between a pair of undoped InGaAsP barrier layers. With suitable doping concentration and thickness of the delta-doped barrier layer, we have demonstrated MQW lasers with To as high as 82 K.

Abstract: The specification describes a lift-off technique useful in the manufacture of III-V semiconductor devices such as MQW lasers. The lift-off step is improved by a spacer layer of III-V semiconductor that can be non-selectively etched to form a mesa stripe, and selectively etched for the lift-off step. The spacer layer allows the etch mask to be dimensionally adjusted to reduce or eliminate overhang of the mesa, and prevent adverse shadowing effects. MBE is effective for both growing the multilayer stack and regrowing the blocking layer. A self-aligned mask on the multilayer stack can be produced by removing the overhang, and facilitating lift-off by producing an undercut in the III-V spacer layer using selective etching.

Abstract: A multiple wavelength quantum cascade (QC) superlattice (SL) light source has at least three energy levels in each radiative transition (RT) region, and electron transitions between the levels give rise to emission lines at different wavelengths. In one embodiment, a lower miniband has at least a first energy level and an upper miniband has at least third and fourth energy levels. In another embodiment, the lower miniband has first and second energy levels. In both cases, electron transitions between a first pair of the upper and lower levels generates light at a first spontaneous emission line having a center wavelength .lambda..sub.1 and a line broadening first energy, and electron transitions between a second pair of the upper and lower levels generates light at a second spontaneous emission line having a center wavelength .lambda..sub.2 and a line broadening second energy.

Abstract: The quantum cascade (QC) photon source according to this invention can emit simultaneously at two distinct wavelengths, typically both in the mid-infrared. This is accomplished through provision of a semiconductor layer structure in which, at the proper bias voltage, electrons are injected into an energy level E.sub.3 and then forced to cascade through an intermediate level E.sub.2 before reaching the ground state E.sub.1 of the active region. In the process, photons of energy E.sub.3 -E.sub.2 (wavelength .lambda..sub.1) and E.sub.2 -E.sub.1 (wavelength .lambda..sub.2) are emitted. Dual wavelength photon sources according to this invention can be used in a variety of ways, e.g., to determine the absorption of a gaseous sample at wavelengths .lambda..sub.1 and .lambda..sub.2, exemplarily to determine the concentration of a particular chemical compound in the sample.

Abstract: A novel quantum cascade (QC) laser comprises a multiplicity of identical repeat units, with each repeat unit comprising an active region and an injector region. The injector region comprises quantum wells and barriers, selected to facilitate, under appropriate bias, resonant carrier transport from a lower energy level of a given active region to an upper energy level of an adjacent downstream active region. Carrier transition from the upper energy level to a lower energy level of an active region results in emission of infrared radiation. The laser is advantageously used in, e.g., a measurement system for detection of trace compounds in air.

Abstract: A solid state laser comprises a cavity resonator in the form of a generally cylindrical body and, located within the resonator, an active region which generates lasing light when suitably pumped. The resonator has a relatively high effective refractive index (n>2 and typically n>3) is sufficiently deformed from circularity so as to support at least one librational mode (e.g., a V-shaped or a bow-tie mode, the latter being presently preferred for generating relatively high power, directional outputs). Specifically described is a Group III-V compound semiconductor, quantum cascade (QC), micro-cylinder laser in which the resonator has a flattened quadrupolar deformation from circularity. This laser exhibits both a highly directional output emission and a three-order of magnitude increase in optical output power compared to conventional semiconductor micro-cylinder QC lasers having circularly symmetric resonators.

Abstract: The specification describes a method for producing black phosphorus from red phosphorus by thermally cycling red phosphorus in a vacuum between 360-400.degree. C. and 200-240.degree. C., whereupon the red phosphorous undergoes an allotropic phase change to black phosphorus.

Abstract: A novel superlattice quantum cascade (SLQC) laser has undoped SL active regions, with the dopant concentration in the injector region being selected, such that, under an appropriate electrical bias, the SL active region is substantially electric field free. The absence of dopant atoms in the SL active region results in reduced carrier scattering and reduced optical losses, with consequent low threshold current and/or room temperature operation. The novel laser emits in the mid-IR spectral region and can be advantageously used in measurement or monitoring systems, e.g., in pollution monitoring systems.

Abstract: Instead of trying to keep the SLs of a QC laser field free, we "pre-bias" the actual electronic potential by varying the SL period (and hence average composition) so as to achieve an essentially flat profile, on average, of upper and lower minibands, despite the presence of an applied field in the SLs. In one embodiment, in at least a first subset of the QW layers, the thicknesses of the QW layers are varied from QW layer to QW layer so as to increase in the direction of the applied field. In this embodiment, the upper and lower lasing levels are located, in the absence of an applied electric field, each at different energies from layer to layer within the first subset, so that despite the presence of an applied field, the desired flatband condition of the upper and lower minibands is realized.