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We present a novel approach to determine the individual layer thickness in a dielectric multilayer sample using pulsed terahertz spectroscopy in reflection geometry. In a first step, the optical parameters of each layer have to be determined. Based on these parameters, we simulate the reflected THz-pulse from the multilayer system and compare it to the measurement. A genetic algorithm is used to determine...
Optical pump-terahertz probe spectroscopy was used to study the key electronic properties of GaAs, InAs and InP nanowires at room temperature. Of all nanowires studied, InAs nanowires exhibited the highest mobilities of 6000 cm2V−1s−1. InP nanowires featured the longest photoconductivity lifetimes and an exceptionally low surface recombination velocity of 170 cm/s.
Structural evolution with temperature of tetraphenylethene (TPE) is followed using THz-TDS. The observed changes in the terahertz spectra are rationalized by performing DFT calculations on experimentally determined low and high temperature crystal structures, thus allowing the changes to be rationalized in terms of the subtle changes in the supramolecular structure.
Collagen sheets were prepared from sea cucumber and their absorption properties were measured at terahertz frequencies. Adding salt to the collagen sheet caused the spectral shape to noticeably change at around 170 cm−1, and this change was related to the contraction and condensation of collagen fibers.
Terahertz time domain spectroscopy has been used to characterize various tissues in biomedical research to date. In this paper the terahertz properties of three groups of rat skin tissues treated with different injections (normal saline control, high dose of Dotarem, and high dose of Omniscan) are measured. The difference in terahertz properties of the tissues can be clearly observed from the results.
Development and applications of one-pulse time-domain spectroscopy on terahertz Novosibirsk free-electron laser is described. Spectrometer with Fabry-Perot etalon in reference branch is used for NovoFEL pulse diagnostics with measuring time of 0.4–0.5 ns. More long HCN-gas reference was applied for high resolution (38 MHz; 1.8·10−5) gas spectroscopy. Spectral resolution of the method as expected to...
We report on a newly developed and integrated microscopy and nanoscopy station at the ANKA-IR2 beamline. We further elucidate how vibrational near-field and micro-spectroscopy can give new insights in medical applications.
Terahertz time domain spectroscopy in the range 0.3–1.5 THz has been conducted for D-glucose at physiological concentrations from 25–200 mg/dL in pure water and in 0.9% saline by mass. The results show that the ions do not uniformly affect absorption of aqueous glucose, so NaCl ions should not be modeled simply as transparent holes in the water framework.
I will briefly review the history of THz free-electron lasers (FEL) as versatile sources for semiconductor spectroscopy and present some recent experiments using the FEL in Dresden.
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...
Terahertz spectroscopy of human hair has attracted much interest in fields such as biochemistry of biopolymer fiber, nondestructive food inspection, and monitoring health condition. We have measured human hairs by two orthogonal polarization directions with transmission terahertz time-domain spectroscopy (THz-TDS) in 0.2 to 3 THz band, and detected a difference between spectra of the two polarizations...
A THz spectrometer based onto the photomixing technique associated with a femtosecond frequency comb is a perfect tool for the study of radicals, which usually required a very large tunability. The spectra of OH, SH and SO have been revisited and updated data have been obtained.
Activation energy of phospholipids in aqueous solution was obtained by terahertz (THz) time domain spectroscopy. The THz absorption as a function of temperature, an Arrhenius plot, yields activation energy of water relaxation process. Head group structure and phase dependence of the activation energy is reported.
THz spectroscopy is a promising technique to study intermolecular interactions and molecular dynamics in organic crystals. In this work, aromatic thiourea compounds with methyl substituents were used as model systems to study the intermolecular interactions between aromatic rings and the dynamics of the methyl internal rotation which falls into the terahertz region. The THz spectra of two phenylthiourea...
Following an established concept of IR spectroscopy, the total absorber was transferred to the THz wavelength. This allows for measurement of effects interesting for life-science applications like DNA hybridization and molecular resonances. The complete process from simulations to measurements will be addressed.
Temperature dependence of FID signal emitted by AFM in NdFeO3 is investigated by employing THz time-domain spectroscopy. Our results reveal that Γ4→Γ24 phase transition occurs around T1=170 K, and both two phases have the same AFM resonant frequency of 0.485 THz. The frequency softening is observed for Γ24→Γ2 occurring around T2=110 K.
We studied salt effects on hydration water of protein using terahertz time-domain spectroscopy (THz-TDS). The number of hydration water molecules at the protein surface was observed to decrease by addition of ammonium sulfate, while ammonium thiocyanate increases it.
The potential of terahertz spectroscopy in distinguishing aromatic carbon compounds in bio-chars is demonstrated. Several types of biochar samples were measured and compared with the THz spectra of pure aromatic compounds. Infrared spectra were modeled with B3LYP and mP2PLYP methods. Modeling could not identify accurately each of the absorption lines. However modeling shows that one of the lines close...
We measured terahertz (THz) emission from the vertically aligned indium arsenide (InAs) nanowires using THz time-domain spectroscopy. The photoexcited InAs nanowires were grown by metalorganic chemical vapor deposition on type <111> silicon substrate. Experimental results shows that THz emission mechanism of InAs nanowires are very different from that of bulk InAs substrates.
By combining a UTC-PD as a THz emitter and a 400 GHz Schottky-based heterodyne detection, we realized an indoor THz link working up to 22 Gbps at 400 GHz carrier frequency with ultra-low THz power. The eye diagram at receiver is clearly opened are the system is working with only 1 µW received THz power.
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