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A calorimetric power meter has been developed for the highly accurate power measurement of terahertz spatial light. A solid-state terahertz absorber is used when constant terahertz wave absorption occurs due to the dielectric loss of the absorber and the sensor frequency sensitivity can be calibrated by measuring the reflectance characteristics of the absorber in the terahertz region. The stable absorption...
We report the calculations and measurements of intramolecular vibrational modes and their dependence on inhibitor binding in the THz range. We see an increase in anisotropic THz absorption at low frequency with inhibitor binding in both the measurements and calculations. This surprising result suggests an increase in flexibility with binding. We will discuss the possible reasons for this discrepancy.
We present a computationally efficient and accurate design technique for waveguide slotted arrays. The design technique is verified through measurements of a frequency-scanned antenna operating over the 275 to 295 GHz frequency range that has been fabricated using the PolyStrata® microfabrication process. Distribution Statement “A” (Approved for public release, Distribution Unlimited).
The antenna pattern of a linear Vivaldi antenna array fabricated for G-band (140–220 GHz) radar applications was measured to explore the performance of a novel fabrication technique that allows for miniature waveguide to 3D AirCoax transitions and small footprint millimeter wave RF networks without the need of a substrate. The array includes four Vivaldi elements fed through a 4:1 equal split power...
We are studying resonant-tunneling diodes (RTDs) with strong back injection of electrons from collector into quantum well. Such RTDs exhibit large negative differential conductance and they operate up to 1.46 THz in oscillators.
Optimizing high-power ultrashort pulse amplifier using double-clad Yb-doped fiber, maximum output power of >3 W with a pulse width of 110 fs without pedestal component is obtained. Using this pulse, high-power high-efficiency broadband THz pulse generation is expected.
Detection of explosives has always been an important fact for homeland security. Terahertz spectroscopy and imaging is an emerging, promising candidate in this field. We use time domain THz spectroscopy and we demonstrate that a methodology based on chemometrics is successful for discrimination of explosives and prediction of their concentration in complex samples made by mixture of products.
This paper presents a measurement-based analysis of operation of an example MOSFET detector integrated with a narrow-band patch antenna. First, responsivity of the detector was measured versus frequency of incident wave revealing two responsivity peaks, and then the antenna and the transistor were on-wafer probed to extract their impedances and antenna resonances in order to better explain the behavior...
Measurements of the absorption coefficients α of K+ —, Li+ — and Na+ — montmorillonites in the 0.2 to 1.4 THz frequency band are reported. The absorption of THz-radiation by K+ — montmorillonite is notably weaker than the absorption of THz-radiation by Li+ — and Na+ — montmorillonites. The observed difference of THz absorption coefficients is explained by the naturally lower water content of K+ —...
The injection-seeded terahertz parametric generation (is-TPG) spectroscopy is a new powerful technique that can be used for sample identification including inspection of drugs hidden inside mail envelopes. In the present paper algorithms of automatic sample identification on the basis of measured absorption spectra are discussed. We check the applicability of these algorithms for identification of...
The effective cavity length of megawatt-class gyrotrons for thermonuclear fusion plasma heating with cavity quality factors in the range of 1000 to 2000 cannot be deduced just from the cavity field profile, since this has by far not a Gaussian contour. This report presents a novel method to determine the effective length of a high-power gyrotron cavity from the eigenvalue of the operating mode, the...
A compact, robust, and reliable broadband receiver has been developed for the ITER ECE diagnostic system. The system provides continuous diagnostic coverage of the 200–300 GHz band using all solid-state components and less than 10W total power dissipation.
This paper presents the design, fabrication and characterization of a terahertz (THz) spoof surface plasmon based near field probe. It is built using a single side metalized bulls-eye plastic structure with a micro-lens at the aperture. 3-D printing is used in the fabrication of the plastic structure followed by a thin film metal coating. Details analysis is carried out using FEM simulation tool....
Using terahertz time-domain spectroscopy (THz-TDS), we measured optical constants of nine different types of common natural stones: slate, gneiss, marble, mudstone, sandstone, dolomite, granite, tuff, and diorite. The result shows that most natural stones are fairly transparent in THz frequency range, and dolomite, in particular, exhibits a nearly uniform refractive index of 2.7 over frequency range...
Heterodyne receivers at millimeter and submillimeter wavelength are widely used for radiometric spectral line observations for atmospheric remote sensing or radio astronomy. The quantitative analysis of such observations requires an accurate knowledge of the mixers's sideband ratio. In addition, its potential sensitivity to spurious harmonics needs to be well understood. In this paper, we discuss...
THE upcoming nuclear fusion plants, such as ITER, pose new challenges under many scientific and technological fields. The requirements of the materials suitable for the operations in such facilities often involve optical, thermal and mechanical characteristics. It's the case of the diamond windows, whose outstanding performances make them the ideal choice as vacuum and tritium barriers inside the...
Evaluation of the effect of the protective case of an antenna on wave propagation by measurement is difficult when the wave length is 1 mm such as for a frequency of 300 GHz. Thus, evaluation based on simulation is required and electric parameters such as the complex relative permittivity are needed for the simulation. In this study, we first constructed a system for measuring complex relative permittivity...
Attenuated total reflection spectroscopy is an accurate method for investigating the complex dielectric properties of polar liquids. In this contribution the error sources from phase instability and angular alignment uncertainty are studied. A novel method to compensate the errors is demonstrated.
In a continuous-wave terahertz spectrometer, we employ photomixing of three lasers, allowing us to measure at three terahertz frequencies simultaneously. Whilst two of the terahertz frequencies can be tuned to obtain terahertz spectra, one terahertz frequency remains fixed. The data recorded at the fixed frequency is used to normalize the spectra of the two other frequencies. As a result, the accuracy...
A highly efficient terahertz photoconductive antenna (THz-PCA) has been developed as a wideband terahertz detector for terahertz time-domain spectroscopy (THz-TDS) systems with a periodic bias line structure to remove unwanted reflections and enhance the frequency resolution. This novel THz-PCA is characterized in a THz-TDS system using a 100 fs optical pulse excitation from which a terahertz pulse...
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