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A terahertz absorption spectrometer with a quantum-cascade laser (QCL) for high-resolution molecular spectroscopy is realized. The spectrometer is based on high-frequency (up to 50 MHz) modulation of the QCL frequency. This allows for the determination of the absorption coefficient and dispersion of the absorbing medium along with a very precise measurement of the line shape of the absorption feature...
We investigate the photothermoelastic response of ZnTe and GaP crystals irradiated by THz-frequency radiation from a quantum cascade laser. We present a full theoretical description of this interaction that agrees well with the measured response.
Video-rate THz reflection imaging, at 450 GHz using a high-resolution INO 384×288 pixel camera core, of pills in blister packs further contained within their final commercial packages is reported. These results open the door to deployable real-time THz cameras for see-through imaging applications, providing a tool for NDE quality control and security inspection of goods within their final packaging.
We fabricated a few periods of THz-QCL structures with small areas to investigate the formation of high-field domains that may prevent laser oscillations. The current-voltage characteristics for a two-well THz-QCL structure did not show any signs of the formation of high-field domains.
Investigation into emission of THz radiation in narrow gap HgCdTe layers and QWs is presented. The results are compared with THz photoconductivity spectra and relaxation kinetics. A possibility of THz lasing in CdHgTe waveguide QW structures is discussed.
Terahertz quantum cascade lasers (THz QCLs) are a promising semiconductor THz source to realize the expected widely compact size THz applications. Currently limitation of THz QCLs is the limited maximum operation temperature (Tmax) and the extension of the operation frequency. Here we propose one Al0.175Ga0.825As/GaAs indirect injection design QCLs operated near 1.9 THz with 160 K. Indirect scattering...
We present a terahertz quantum cascade laser providing 875 mW two-facet output power in pulsed mode, at a frequency around 4.7 THz and at a heatsink temperature of 10 K. The laser has a single plasmon waveguide. The active region is based on four quantum wells with longitudinal optical phonon extraction.
Antenna-coupled field effect transistors have been developed as plasma-wave THz detectors in both InAs nanowire and graphene channel materials. Room temperature operation has been achieved up to 3 THz, with noise equivalent power levels < 10−10 W/Hz1/2, and high-speed response already suitable for large area THz imaging applications.
Mode profiles, transmission attenuation and dispersion in flexible dielectric-lined hollow metallic cylindrical waveguides are analyzed experimentally and numerically. Using dielectric coatings made of different materials and different thicknesses, we show the crossover between the fundamental TE11 and TM11 modes and the hybrid HE11 mode.
The intrinsic linewidth of Surface Plasmon Polariton resonance in a micrometric metal mesh has been measured with a collimated mid-infrared beam, provided by an External-Cavity, tunable Quantum Cascade Laser. The use of a collimated beam yields a resonance linewidth of 12 cm−1, much narrower than by conventional black-body sources. This opens more favorable perspectives to the use of metal meshes...
For the researches of input structure of confocal quasi-cylindrical gyrotron amplifier with frequency at 220GHz, the parameters of input structure are optimum with a help of CST studio. The input structure including WR4 waveguide, WR2.8 waveguide, 90o circle waveguide and confocal quasi-cylindrical waveguide are studied. The results show that the TE06 mode is obtained in confocal quasi-cylindrical...
We report on the first demonstration of a quartz enhanced photo-acoustic (QEPAS) sensor in the Terahertz (THz) range. The sensor is based on a QCL emitting at 3.93 THz and a customized quartz tuning fork. For methanol detection we reached a normalized noise-equivalent absorption of 2×10−10 cm−1W/Hz½ comparable with the best result of mid-IR QEPAS.
We use an ultrafast NbN superconducting detector to investigate dynamic bulk heat-storage effects in a THz QCL. A first-order heat-accumulation model is used to obtain reliable estimates of the thermal resistance and heat capacity from the measured temperature variation.
A fundamental 1.9–2.8 THz Schottky diode mixer has been modified to enable high harmonic mixing, thus allowing use of the mixer for phase locking of a quantum cascade laser (QCL) to an stable external microwave source. Phase locking to a reference will transfer the spectral line profile of the reference to the THz source; this will control the phase precisely. Stabilizing a QCL for a single frequency...
We report on a phase locking experiment of a 3.4 THz Quantum Cascade Laser (QCL) by using only room temperature electronics. A super-lattice harmonic mixer was used to produce a bit signal between the QCL signal and the 18th harmonic of a 190 GHz reference generator. The beat signal more than 30 dB above the noise level for 1 MHz RBW was observed. Such a signal to noise ratio was sufficient to provide...
We report on injection induced terahertz electroluminescence from SiC p-n junctions. The emission is assigned to intracenter optical transitions in shallow donors, initiated by the injection.
A heterogeneous THz-QCL is used for diffuse-reflectance imaging of powdered solids at 4 frequencies in the range 3.05–3.35 THz. An effective-optical-path-length model reproduces TDS absorption spectra accurately and discriminates between admixtures of materials with differing concentrations.
A terahertz transmission imaging system based on a quantum-cascade laser (QCL), a fast scanning mirror, and a sensitive Ge:Ga detector is demonstrated. In order to reduce artifacts, special care was taken on the optics and the conversion of the measured data into the image. Images with a diameter of approximately 40 mm and a signal-to-noise ratio of up to 28 dB were obtained within 1.1 s. The system...
Quantum Cascade Lasers are promising sources of Terahertz radiation. Picosecond pulses generation with these lasers is currently at its infancy and their detection is difficult. An intensity electro-optic sampling method is used here to demonstrate 19ps FWHM pulses from a QCL via active modelocking.
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