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KIDCAM is demonstration of a deployable cryogen-free passive THz imaging technology. A linear focal plane array of Lumped Element Kinetic Inductance Detectors (LEKIDs) is cooled to sub-K temperatures without the consumption of liquid cryogens. The instrument offers extremely high detection sensitivity with video frame rate capability and high spatial resolution to suit many imaging applications. The...
Terahertz in-line and reference-beam holography has been implemented using the Novosibirsk free electron laser as a source of monochromatic radiation. Holograms of amplitude and phase objects were recorded with temperature-sensitive phosphor image plate. Spatial resolution of the reconstructed images was about 0.4 mm at a wavelength of 0.13 mm.
A 10 MW, 140 GHz ECRH system with a pulse duration of 30 minutes is currently under construction for the stellarator W7-X at Greifswald. The RF power will be provided by 10 gyrotrons. A European collaboration has been established to develop and build 9 (out of 10) tubes each with an output power of 1 MW for continuous wave (CW) operation. This contribution reports on recent progress with the series...
A reconfigurable, all-reflective terahertz imager has been constructed, capable of 4096-pixel resolution in 20 seconds. The imager spans 0.09–0.90 THz in 5 bands, each represented by a 16-element detector array. Both, beam profiling and confocal imaging configurations have been demonstrated.
We observed detailed spectrum of THz frequency comb by extending the measured time window of the pulsed THz electric field up to ten pulse periods with asynchronous-optical-sampling THz-TDS (ASOPS-THz-TDS). Observed spectrum of THz comb mode has a linewidth of 5.6 MHz and a frequency interval of 56 MHz.
Carrier dynamic for Be doped multi-quantum-well InGaAs-InAlAs material systems are measured using an infrared pump-probe measurement system at 1550 nm wavelength range. The carrier life-time for as-grown materials and for materials with two different levels of Be doping annealed at different temperatures are measured and the results are compared. Subpicosecond carrier lifetimes are obtained.
Terahertz radiations are well suited to detect material structural defects. This paper presents an approach aimed to detect and align 3D shapes, from terahertz tomographies, with the corresponding CAD model. This is a fundamental step to subsequently achieve an automatic process of flaws detection and geometrical measurement of the component.
A flexible terahertz (THz)-time domain spectroscopy (TDS) system has been fabricated by using air guided photonic crystal fibers for 1.56 μm laser and a DAST crystal as an emitter. Using this system we could obtain reliable refractive index value n of Si in the frequency ranges from 0.2–2.8 THz.
A new dual-frequency quasi-optical mode conversion system for a step-tunable gyrotron is discussed. The design methodology improves upon those for previously reported designs in that the optimization of the launcher and mirror system have been integrated, and power losses within the mirror system are explicitly minimized.
Transmittance measurements on micro- and nano-sized powdered barium ferrite (BaFe12O19) and strontium ferrite (SrFe12O19) have been studied in a broadband millimeter wave frequency range for the first time. Measurements have been performed using a free space quasi-optical millimeter wave spectrometer, equipped with high power backward wave oscillators as sources of tunable coherent radiation. A tunable...
We have carried out a theoretical and computation study of optical response of bilayer graphene in the terahertz regime. It is found that the optical response of bilayer graphene can be significantly enhanced by nonlinear process for fields greater than 1000v/cm. The optical nonlinearity of bilayer graphene persists even in room temperature. This suggests that bilayer graphene can potentially be utilized...
A fast-scanning tunable Fabry-Perot filter has been developed for signature identification in reflective THz sensor systems. The reflectors are metal mesh filters having reflectivity between 0.90 and 0.95, depending on the specific frequency. A demonstration of the filter has been carried out at 530 GHz with a resolution of ∼10 GHz (Q ∼ 50), a scan range of ∼50 GHz, and a scan time of 0.5 seconds...
A principal model of a high-frequency modulator of infrared radiation working at different temperatures has been created. The modulator is working on the magnetorefractive effect near the Curie temperature of magnetoresistive manganite films in the middle infrared spectral range.
The generation of terahertz pulses in nonlinear optical crystals by optical rectification of laser pulses is a common and known method. So called LO-TO splitting can be a measure of the crystal ability to show nonlinear properties. A series of organic crystals along different crystallographic directions has been investigated.
Perylene 3,4,9,10-tetracarboxylic dianhydride (PTCDA), one of the perylene derivatives, has many absorption peaks in the THz region. Density functional theory (DFT) analysis of the crystal geometry elucidated that intermolecular vibrations of relative rotation and translation, and intramolecular vibrations of torsion and bending dominate below and above 2 THz, respectively. The frequency shifts relative...
In this report we present our experimental study on a super-focusing effect of a V-groove metallic structure for THz pulsed waves. Without using coupling lens, a 17% amplitude transmission of THz broadband waves (0∼2.5 THz) through a 2-μm bottom-width was observed without significant waveform distortion and phase delay.
A torus diamond window prototype for an ITER electron cyclotron heating and current drive (EC H&CD) system was fabricated based on the latest design. It was installed in the ITER relevant transmission line and high power-long pulse experiment was carried out. Transmission of 740kW–100sec and was performed. It was observed that the cooling water temperature was stabilized and significant low loss...
We demonstrated a fiber-coupled THz time-domain spectroscopy (TDS) system. A THz output power of 132 nW of the THz emitter in the system was measured by a Golay-cell. Water vapor dips in the free space were clearly observed by the THz detector in the system.
Reflection measurements of pigments used in artworks will be performed in the THz spectral range, utilizing the THz sources available at the ENEA research center of Frascati in collaboration with CISA3, University of California.
In this work, terahertz spectroscopy was used to study the hydrogen bonding behaviour in mixtures of ethyl lactate and water. The results obtained show a marked deviation from a two-phase system, which agrees with data from other techniques.
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