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We present an analytical model carefully describing the time-frequency behavior of all the stages composing our whole Terahertz Time Domain Spectroscopy laser based system, from the THz pulses generation via Optical Rectification, to their detection through Electro-Optic Sampling technique, by way of diffraction, collecting and focusing effects. In order to prove the effectiveness of our work, we...
We investigate the ion effect on 1, 2-ditetradecanoyl-sn-glycero-3-phosphocholine lipid hydration with attenuated total reflection terahertz time domain spectroscopy. The absorption difference between lipid solutions and buffers (water and NaCl solution) shows that lipid-ion interaction accelerates the water reorientation motion confined in nanometer scale structure.
Intense terahertz pulses are used to investigate nonlinear carrier dynamics in Au thin films with different morphologies. From THz field-dependent transmission measurements, we found that the conductivity in percolated Au nanostructures increases with increasing the incident field strength. The measured complex dielectric dispersion was analyzed using the Drude-Smith model to discuss the dynamics...
We propose a novel THz material analysis approach which consists of a combination of a stratified dispersive model, an appropriate measurement configuration and a time-domain based fitting procedure. The measurement configuration is modeled as a stratified system where for each layer the light-matter interaction is realistically described. The method is illustrated for the industrial quality control...
We present experimental results from the application of terahertz time-domain spectroscopy in diagnosis of scald burns in a standardized porcine model in a clinical Operating Room setting. Superficial, deep partial-thickness and full-thickness burns were differentiated according to the spectral information between 0.2 and 0.8 THz. The severity of wounds were quantified based to the depth of the burned...
We present a design of periodically arranged microslits in a gold film for nonlinear terahertz phonon spectroscopy. Global optimization of array parameters gives a field enhancement of more than 50, due to plasmonic coupling between individual slits.
The THz/FarIR beamline at the Australian Synchrotron is currently extending its capabilities to includes lasers. These lasers could be used for photolysis, pyrolysis or steady state pump/probe experiments. We currently have a high powered cw CO2 laser and a pulsed YAG laser.
We investigated the transient response of the solvated electron ejected by photodetachment from potassium ferrocyanide in water using time resolved terahertz spectroscopy (TSTS). We find that the measured frequency dependent conductivity can be well described by a Drude-Smith model, supplemented by a Lorentz model oscillating near 5 THz.
Gyrotrons have demonstrated operation at frequencies above 1.0 THz both in pulsed and cw operation. An important present-day application of THz gyrotrons is in the field of Dynamic Nuclear Polarization/Nuclear Magnetic Resonance spectroscopy, providing enhanced NMR signals at high magnetic fields. THz gyrotrons have the potential for providing narrow bandwidth, high power coherent radiation at frequencies...
The analysis of petrochemical samples by Terahertz (THz) spectroscopy is investigated. THz spectroscopy is a nondestructive, contact-free analysis method for the study of many different materials. In this work, we show that the THz spectra can be used to get different chemical and structural information from a potential hydrocarbon source. Density of the geological samples has the potential for valuable...
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.
Topological insulators represent a new state of matter where bulk insulators exhibit metallic surfaces that are protected by time reversal symmetry. However, in common transport measurements residual bulk conductivity hinders the properties of the topologically protected surfaces. Alternatively, terahertz spectroscopy has recently been shown to be capable of discerning the bulk and surface carrier...
Terahertz time-domain spectroscopy was used as a nondestructive and a noncontact optical probe to investigate the material properties and high frequency carrier dynamics of undoped and Al-doped ZnO nanowires (NWs). The frequency dependent refractive index was first determined through effective medium theory and numerical iteration process applied to the detected terahertz signals transmitted through...
Terahertz ellipsometric and polarimetric measurement systems have been commissioned with the Novosibirsk free electron laser (FEL) being a source of monochromatic radiation. Calibration experiments with semiconductors and metamaterials showed correct operation of these systems. Blood films, monosaccharide, amino acids, and culture medium were studied.
Propagation of a pulse THz radiation through molecular gas mediums has series of features. In the paper three of them (giant light speed reduction, commensurate echoes, and non-Faraday rotation of polarization) are presented. The effects were measured directly in real time by a powerful pulse radiation of the Novosibirsk terahertz free-electron laser and our ultrafast detection technique.
This paper describes the application of multivariate analysis (MVA) techniques to terahertz (THz) gas-phase absorption spectra at around 245 GHz. The THz spectra of gaseous volatile organic compounds (VOCs) and their complex mixtures at pressures between 10 and 5000 Pa were acquired with a vector network analyzer (VNA) and an absorption cell. With the subsequent MVA our experiment shows the feasibility...
A monochromatic continuous wave terahertz source with widely tunable frequency range and high resolution has been used to measure the water absorption spectrum at temperatures up to 500 °C. Experiments are carried out based on the HITRAN simulation at different humidity levels. The whole THz spectroscopy system was validated with a strong absorption peak at 0.557 THz (18.38 cm−1) that appears at both...
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+ —...
THz and mid IR spectroscopy of high molecular PE (HMW) and ultra high molecular PE (UHMW) reveals modifications of the molecular structure induced by γ-Co60 radiation. UHMW-PE and HMW-PE can be distinguished. The integral absorption in the B1u THz-region can quantitatively describe the amorphization of crystallinity. The formation of trans vinylene unsaturations and the decay of vinyl can be followed...
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...
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