Abstract: The present invention provides a photodiode comprising a p-i-n or pn junction at least partly formed by first and second regions (2) made of semiconductor materials having opposite conductivity type, wherein the p-i-n or pn junction comprises a light absorption region (11) for generation of charge carriers from absorbed light. One section of the p-i-n or pn junction is comprises by one or more nanowires (7) that are spaced apart and arranged to collect charge carriers generated in the light absorption region (11). At least one low doped region (10) made of a low doped or intrinsic semiconductor material provided between the nanowires (7) and one of said first region (1) and said second region (2) enables custom made light absorption region and/or avalanche multiplication region of the active region (9).

Abstract: Apparatus and methods for generating radiation via difference frequency generation (DFG). In one exemplary implementation, a quantum cascade laser (QCL) has a significant second-order nonlinear susceptibility (?(2)) integrated in an active region of the QCL. The QCL is configured to generate first radiation at a first frequency ?1, second radiation at a second frequency ?2, and third radiation at a third frequency ?3=?1??2 based on difference frequency generation (DFG) arising from the non-linear susceptibility. In one aspect, the QCL may be configured to generate appreciable THz radiation at room temperature.

Abstract: A mid infrared spectrometer comprises a high brightness broadband source that generates an output with a broad spectral range in the order of hundreds of wave numbers, a wavelength dispersive element and a detector. In one embodiment, the source comprises an array of semiconductor laser devices operating simultaneously. Each device emits light at wavelength different from the wavelengths emitted by the other devices in the array and the devices are arranged so that the combined output continuously covers the broad spectral range. In another embodiment, each of the lasers in the array is a quantum cascade laser device. In still another embodiment, the quantum cascade laser devices in the array are operated in the regime of Risken-Nummedal-Graham-Haken (RNGH) instabilities. In yet another embodiment, each of the lasers in the array is a mode-locked quantum cascade laser device.

Abstract: A broadly tunable single-mode infrared laser source based on semiconductor lasers. The laser source has two parts: an array of closely-spaced DFB QCLs (or other semiconductor lasers) and a controller that can switch each of the individual lasers in the array on and off, set current for each of the lasers and, and control the temperature of the lasers in the array. The device can be used in portable broadband sensors to simultaneously detect a large number of compounds including chemical and biological agents. A microelectronic controller is combined with an array of individually-addressed DFB QCLs with slightly different DFB grating periods fabricated on the same broadband (or multiple wavelengths) QCL material. This allows building a compact source providing narrow-line broadly-tunable coherent radiation in the Infrared or Terahertz spectral range (as well as in the Ultraviolet and Visible spectral ranges, using semiconductor lasers with different active region design).

Abstract: An apparatus for collimating radiation can include an aperture of subwavelength dimensions and a neighboring set of grooves defined on a metal film integrated with an active or passive device that emits radiation. Integration of the beam collimator onto the facet of a laser or other radiation-emitting device provides for beam collimation and polarization selection. Beam divergence can be reduced by more than one order of magnitude compared with the output of a conventional laser. An active beam collimator with an aperture-groove structure can be integrated with a wide range of optical devices, such as semiconductor lasers (e.g., quantum cascade lasers), light emitting diodes, optical fibers, and fiber lasers.

Abstract: The solar cell structure according to the present invention comprises a nanowire (205) that constitutes the light absorbing part of the solar cell structure and a passivating shell (209) that encloses at least a portion of the nanowire (205). In a first aspect of the invention, the passivating shell (209) of comprises a light guiding shell (210), which preferably has a high- and indirect bandgap to provide light guiding properties. In a second aspect of the invention, the solar cell structure comprises a plurality of nanowires which are positioned with a maximum spacing between adjacent nanowires which is shorter than the wavelength of the light which the solar cell structure is intended to absorbin order to provide an effective medium for light absorption. Thanks to the invention it is possible to provide high efficiency solar cell structures.

Abstract: Apparatus and methods for generating radiation via difference frequency generation (DFG). In one exemplary implementation, a quantum cascade laser (QCL) has a significant second-order nonlinear susceptibility (?(2)) integrated in an active region of the QCL. The QCL is configured to generate first radiation at a first frequency ?1, second radiation at a second frequency ?2, and third radiation at a third frequency ?3=?1??2 based on difference frequency generation (DFG) arising from the non-linear susceptibility. In one aspect, the QCL may be configured to generate appreciable THz radiation at room temperature.

Abstract: A quantum cascade laser utilizing non-resonant extraction design having a multilayered semiconductor with a single type of carrier; at least two final levels (1 and 1?) for a transition down from level 2; an energy spacing E21 greater than ELO; an energy spacing E31 of about 100 meV; and an energy spacing E32 about equal to ELO. The carrier wave function for level 1 overlaps with the carrier wave function for level 2. Likewise, the carrier wave function for level 1? overlaps with the carrier wave function for level 2. In a second version, the basic design also has an energy spacing E54 of about 90 meV, and levels 1 and 1? do not have to be spatially close to each other, provided that level 2 has significant overlap with both these levels. In a third version, there are at least three final levels (1, 1?, and 1?) for a transition down from level 2. Each of the levels 1, 1?, and 1? has a non-uniform squared wave function distribution.

Abstract: A broadly tunable single-mode infrared laser source based on semiconductor lasers. The laser source has two parts: an array of closely-spaced DFB QCLs (or other semiconductor lasers) and a controller that can switch each of the individual lasers in the array on and off, set current for each of the lasers and, and control the temperature of the lasers in the array. The device can be used in portable broadband sensors to simultaneously detect a large number of compounds including chemical and biological agents. A microelectronic controller is combined with an array of individually-addressed DFB QCLs with slightly different DFB grating periods fabricated on the same broadband (or multiple wavelengths) QCL material. This allows building a compact source providing narrow-line broadly-tunable coherent radiation in the Infrared or Terahertz spectral range (as well as in the Ultraviolet and Visible spectral ranges, using semiconductor lasers with different active region design).

Abstract: Briefly, embodiments of a configuration for ultra-low friction is disclosed

Abstract: A new class of photonic devices called active optical antennas, which consist of metallic structures directly integrated on to the facet of a semiconductor lasers, and of instruments based on such antennas are disclosed. The structures consist of metallic elements which function as antennas at optical wavelengths by spatially concentrating laser radiation of wavelength in the range from the UV to the mid-infrared into spots (with sizes in the range 10-100 nm) in the so called near field zone, that is at subwavelength distances from the facet. Various antenna designs are considered depending on the laser under consideration and applications. This invention has wide ranging applications such as new microscopes for high-resolution spatially resolved imaging and spectroscopy, new probes for biology, laser assisted processing and repair of devices, circuits and masks, as well new optical tweezers and phased array devices. Microscopes and other systems based on this invention are discussed.

Abstract: An optoelectronic transducer comprises a unipolar, intraband active region and a micro-cavity resonator. The resonator includes a 2D array of essentially equally spaced regions that exhibits resonant modes. Each of the spaced regions has a depth that extends through the active region and has an average refractive index that is different from that of the active region. The refractive index contrast, the spacing of the spaced regions, and the dimensions of the spaced regions are mutually adapted so that the array acts as a micro-cavity resonator and so that at least one frequency of the resonant modes of the array falls within the spectrum of an optoelectronic parameter of the active region (i.e., the gain spectrum where the transducer is a laser; the absorption spectrum where the transducer is a photodetector). In a first embodiment, the transducer is an ISB laser, whereas in a second embodiment it is a unipolar, intraband photodetector.

Abstract: Embodiments of a laser are disclosed.

Abstract: A broadband CLE capable of operation simultaneously at multiple wavelengths comprises: a core region including a multiplicity or cascade of stages, each stage including a radiative transition region. A first group of stages emits radiation at a first wavelength and at a first aggregate intensity per group, and a second group of stages emits radiation at a second wavelength and at a second aggregate intensity per group lower than the first intensity. The invention is characterized in that the second group has more stages than said first group, and the per-stage intensity of the first group is greater than that of the second group. This design reduces the difference between said first and second aggregate intensities. In one embodiment, groups that are located at or near to the ends of the cascade have more stages than groups that are centrally located within the cascade regardless of their wavelength.

Abstract: A broadband CLE capable of operation simultaneously at multiple wavelengths comprises: a core region including a multiplicity or cascade of stages, each stage including a radiative transition region. A first group of stages emits radiation at a first wavelength and at a first aggregate intensity per group, and a second group of stages emits radiation at a second wavelength and at a second aggregate intensity per group lower than the first intensity. The invention is characterized in that the second group has more stages than said first group, and the per-stage intensity of the first group is greater than that of the second group. This design reduces the difference between said first and second aggregate intensities. In one embodiment, groups that are located at or near to the ends of the cascade have more stages than groups that are centrally located within the cascade regardless of their wavelength.

Abstract: An optoelectronic transducer comprises a unipolar, intraband active region and a micro-cavity resonator. The resonator includes a 2D array of essentially equally spaced regions that exhibits resonant modes. Each of the spaced regions has a depth that extends through the active region and has an average refractive index that is different from that of the active region. The refractive index contrast, the spacing of the spaced regions, and the dimensions of the spaced regions are mutually adapted so that the array acts as a micro-cavity resonator and so that at least one frequency of the resonant modes of the array falls within the spectrum of an optoelectronic parameter of the active region (i.e., the gain spectrum where the transducer is a laser; the absorption spectrum where the transducer is a photodetector). In a first embodiment, the transducer is an ISB laser, whereas in a second embodiment it is a unipolar, intraband photodetector.

Abstract: Techniques for amplifying light produced by a quantum cascade laser are described. An assembly according to the present invention includes an optical amplifier having an optical input and an optical output. The optical output has an area significantly greater than that of the optical output and the geometry of the amplifier is such that the amplifier widens from the optical input to the optical output. The optical amplifier is formed of a layered waveguide structure which achieves quantum confinement of electrons and photons within the active region. A distributed feedback laser is suitably coupled to the optical amplifier at the optical input of the amplifier. The widening of the amplifier makes available a large number of electrons, so that the amplifier is able to produce many photons resulting from stimulated transitions caused by introduction of light to the optical input of the amplifier, even if the great majority of the transitions occur nonradiatively.

Abstract: A monolithic apparatus has a laser optical cavity. The laser optical cavity has a multi-layer structure that includes a first active semiconductor multi-layer and a second semiconductor multi-layer. The second semiconductor multi-layer is located laterally adjacent to the first active semiconductor multi-layer. The first active semiconductor multi-layer includes a sequence of quantum well structures that produce light of a lasing frequency in response to being electrically pumped. The second semiconductor multi-layer includes a sequence of quantum well structures and is configured to both absorb light of the lasing frequency and produce one of parametric light and harmonic light in response to absorbing light of the lasing frequency.

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 an intersubband light emitter, at least two injection/relaxation (I/R) regions contiguous with the same RT region have different doping levels. Preferably, one I/R region has a doping level that is at least 100 times lower than that of the other I/R region. In one embodiment, one I/R region is undoped, whereas the other I/R region is doped.