Abstract: A three-dimensional nanoresonator structure has a stack of laterally confined layers including at least a first layer and a second layer of different conductive materials between which a dielectric layer is interposed. The layers have at least a respective accessible surface area exposed to an environment in which the structure is immersed. Multiple three-dimensional nanoresonators that can be dispersed in an environment are formed from an array of nanoresonators fixed to a sacrificial substrate. The nanoresonators are subsequently separated from the substrate and conjugated with a chemical agent adapted to promote the formation of a stable colloidal suspension of nanoresonators in a liquid medium.

Abstract: A three-dimensional nanoresonator structure has a stack of laterally confined layers including at least a first layer and a second layer of different conductive materials between which a dielectric layer is interposed. The layers have at least a respective accessible surface area exposed to an environment in which the structure is immersed. Multiple three-dimensional nanoresonators that can be dispersed in an environment are formed from an array of nanoresonators fixed to a sacrificial substrate. The nanoresonators are subsequently separated from the substrate and conjugated with a chemical agent adapted to promote the formation of a stable colloidal suspension of nanoresonators in a liquid medium.

Abstract: A semiconductor laser includes a laser resonator (1) having a planar active region (3), a first (2) and a second (6) wave-guide layer that define the active region (3). The resonator (1) has a shape that is defined by a perimeter, along which the first layer (2) radiation guide has a plurality of cuts (4) forming a lattice. The cuts are made as at least two adjacent slits (4a, 4b) and a zone between the slits in which an uncut portion (5a) of wave-guiding layer is present. In the case of a circular semiconductor laser, the number of cuts (4) is a prime number, or an odd number that is a multiple of a prime number, the prime number being greater than or equal to five. This way, it is avoided that resonance modes evolve outside of the zone with the cuts, or in any case with a component that is different from zero of the wave vector in a radial direction, and a pure whispering gallery operating mode is obtained, with maximum of the emitted radiation that evolves in a vertical direction, i.e.

Abstract: A semiconductor laser comprises an active region (12) which, in response to a pumping energy applied thereto, can produce a stimulated emission of radiation with a central wavelength (?) in the far infrared region, and a confinement region (16, 18, 22) suitable for confining the radiation in the active region (12), and comprising at least one interface (16a, 16b, 22a) between adjacent layers that is capable of supporting surface plasmon modes generated by an interaction of the interface with the radiation. The confinement region (16, 18, 22) comprises a wave-guide layer (16) which is delimited on opposite sides by a first interface and by a second interface (16a, 16b).

Abstract: A semiconductor laser comprises an active region (12) which, in response to a pumping energy applied thereto, can produce a stimulated emission of radiation with a central wavelength (?) in the far infrared region, and a confinement region (16, 18, 22) suitable for confining the radiation in the active region (12), and comprising at least one interface (16a, 16b, 22a) between adjacent layers that is capable of supporting surface plasmon modes generated by an interaction of the interface with the radiation. The confinement region (16, 18, 22) comprises a wave-guide layer (16) which is delimited on opposite sides by a first interface and by a second interface (16a, 16b).

Abstract: The measurement of intersubband electroluminescence (ISB-EL) in unipolar quantum cascade lasers is achieved by forming a longitudinal cleave through the active region and waveguide of the QC laser device, exposing a complete side face of the device, including the active region. The conventional laser facets at the entrance and exit of the active region are coated with a highly reflective material and the emission from the exposed side face is measured. In theory, the sideface emission would comprise only the ISB-EL spontaneous emission, but some additional laser emission (due to scattering in the imperfect waveguide structure) also exits along this sideface. Spatial filtering and/or polarization monitoring can be used to differentiate the laser emission from the ISB-EL spontaneous emission.

Abstract: The RT regions of an ISB light emitter comprise pre-biased SLs and a multiplicity of split quantum wells (SPQWs). A SPQW is a quantum well that is divided into a multiplicity of sub-wells by a first barrier layer sufficiently thin that the upper and lower energy states are split beyond their natural broadening and contribute to different minibands in each RT region. In contrast, adjacent SPQWs are coupled to one another by second barrier layers. The thicknesses of the latter layers are chosen so that minibands are created across each RT region. In one embodiment, the emitter includes an I/R region between adjacent RT regions, and in another embodiment the I/R regions are omitted.

Abstract: A surface plasmon laser structure is formed to include a DFB structure as the metal carrying layer, thus forming a single mode surface plasmon laser. The DFB structure comprises a multiple layer metallic surface guiding structure (for example, titanium stripes covered with a layer of gold. forming alternating Ti/Au—Au stripes). The active region, in one embodiment, may comprise a quantum cascade structure.

Abstract: The measurement of intersubband electroluminescence (ISB-EL) in unipolar quantum cascade lasers is achieved by forming a longitudinal cleave through the active region and waveguide of the QC laser device, exposing a complete side face of the device, including the active region. The conventional laser facets at the entrance and exit of the active region are coated with a highly reflective material and the emission from the exposed side face is measured. In theory, the sideface emission would comprise only the ISB-EL spontaneous emission, but some additional laser emission (due to scattering in the imperfect waveguide structure) also exits along this sideface. Spatial filtering and/or polarization monitoring can be used to differentiate the laser emission from the ISB-EL spontaneous emission.

Abstract: In a mesa geometry semiconductor laser, a patterned dielectric coating used to define the stripe geometry contact on the top the mesa and to provide significant waveguiding comprises a chalcogenide glass. Applications to intersubband (e.g., quantum cascade) lasers are specifically described.

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 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 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: 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 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.