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Sample records for terahertz reflection spectroscopy

  1. Terahertz reflection spectroscopy for the detection of explosives

    NASA Astrophysics Data System (ADS)

    Leahy-Hoppa, Megan R.; Fitch, Michael J.; Osiander, Robert

    2008-02-01

    Terahertz (THz) technology has been demonstrated as a promising tool for detection of explosives and is being developed for aviation screening and sensing of improvised explosive devices. THz radiation is attractive for many applications due to its ability to penetrate through a wide range of dielectric materials including clothing, paper, cardboard, plastics, and wood. Of course, metals block THz waves as is the case for microwave, IR, and visible light. Our work has involved investigating the reflection spectroscopy of a variety of materials including explosives such as RDX and PETN, plastic explosive taggants such as DMDNB, and other organic materials. We have also investigated the changes of the reflection spectra in varying grades of sucrose. Spectral differences are observed between three grades of crystalline sugar in the region from 0.1 to 1 THz. By exploiting the unique spectral features, the discrimination capabilities of THz reflection spectroscopy points to the broad applicability of identifying a wide variety of materials.

  2. Reflection terahertz time-domain spectroscopy of RDX and HMX explosives

    NASA Astrophysics Data System (ADS)

    Choi, Kyujin; Hong, Taeyoon; Ik Sim, Kyung; Ha, Taewoo; Cheol Park, Byung; Hyuk Chung, Jin; Gyeong Cho, Soo; Hoon Kim, Jae

    2014-01-01

    We report on our study of RDX and HMX, two of the most commonly used explosive materials, in bulk pellets with reflection terahertz time-domain spectroscopy in the frequency range of 0.3-3 THz. The maximum entropy method was utilized to correct our raw reflection data against the phase error due to the relative displacement between the sample and the reference. Both the refractive index n and the extinction coefficient k in the terahertz region were acquired for these two explosives without a Kramers-Kronig analysis. Both RDX and HMX exhibit a series of distinct peaks not quite detectable in the more conventional transmission-type measurements due to their high terahertz absorptivity. Our results are compared with the literature data on powder samples.

  3. Transmission and Reflection Terahertz Spectroscopy of Insensitive Melt-Cast High-Explosive Materials

    NASA Astrophysics Data System (ADS)

    Palka, Norbert; Szala, Mateusz

    2016-10-01

    Currently, artillery shells and grenades that are introduced into the market are based on melt-castable insensitive high explosives (IHEs), which do not explode while they run a risk of impact, heat or shrapnel. Particles of explosives (such as hexogen, nitroguanidine and nitrotriazolone) are suspended in different proportions in a matrix of 2.4-dinitroanisole. In this paper, we investigated samples of commonly used IHEs: PAX-41, IMX-104 and IMX-101, whose internal structures were determined by a scanning electron microscope. Terahertz time domain spectroscopy was applied in both transmission and reflection configurations. At first, the complex refraction indices of four pure constituents creating IHEs were determined and became the basis of further calculations. Next, the experimentally determined transmission and reflection spectra of IHEs and pure constituents were compared with theoretical considerations. The influence of the grain size of constituent material and scattering on the reflection spectra was analysed, and good agreement between the experimental and theoretical data was achieved.

  4. Extracting Complex Refractive Index from Polycrystalline Glucose with Self-Referenced Method for Terahertz Time-Domain Reflection Spectroscopy.

    PubMed

    Zhang, Yu; Zhang, Lin; Sun, Ping; He, Yingfeng; Zou, Yun; Deng, Yuqiang

    2016-07-01

    A self-referenced method for extracting the complex refractive index of material was proposed. The method utilized signals reflected from the front and rear surfaces of a slice sample as reference and sample signals, respectively. Before using the self-referenced method, a hybrid filtering technique for eliminating systematic and random noises of time-domain terahertz reflection spectroscopy was used. A terahertz reflection spectrum of crystalline glucose was measured and three feature absorption peaks were obtained from 0.2 to 2.0 THz. We suggest that intermolecular vibrational modes may contribute to the observed absorption spectra in the THz frequency range.

  5. Extracting Complex Refractive Index from Polycrystalline Glucose with Self-Referenced Method for Terahertz Time-Domain Reflection Spectroscopy.

    PubMed

    Zhang, Yu; Zhang, Lin; Sun, Ping; He, Yingfeng; Zou, Yun; Deng, Yuqiang

    2016-07-01

    A self-referenced method for extracting the complex refractive index of material was proposed. The method utilized signals reflected from the front and rear surfaces of a slice sample as reference and sample signals, respectively. Before using the self-referenced method, a hybrid filtering technique for eliminating systematic and random noises of time-domain terahertz reflection spectroscopy was used. A terahertz reflection spectrum of crystalline glucose was measured and three feature absorption peaks were obtained from 0.2 to 2.0 THz. We suggest that intermolecular vibrational modes may contribute to the observed absorption spectra in the THz frequency range. PMID:27412185

  6. Evaluation of drug crystallinity in aqueous suspension using terahertz time-domain attenuated total reflection spectroscopy.

    PubMed

    Takebe, Gen; Kawada, Yoichi; Akiyama, Koichiro; Takahashi, Hironori; Takamoto, Hisayoshi; Hiramatsu, Mitsuo

    2013-11-01

    Terahertz pulsed spectroscopy has recently been demonstrated to be a novel technique for the investigation of the solid-state properties of pharmaceutical materials. In this study, we directly measured the crystallinity of a drug suspended in water, using a terahertz pulsed attenuated total reflection (ATR) method. The dihydropyridine calcium channel blocker nifedipine is classified as a poorly soluble drug; its most stable crystalline form is known as form I. Transmission spectra, collected from 0.2 to 2.0 THz (6.6 to 66 cm(-1) ), of nifedipine crystals had a strong absorption peak at 1.2 THz (40 cm(-1) ) at room temperature. When the nifedipine crystals were mixed with poloxamer 188 and suspended in water, the resulting spectra measured using the ATR method had a peak at the same frequency as in the spectra obtained in transmission mode. Furthermore, the peak area was proportional to the amount of crystals. The upward sloping baseline in the spectra, corresponding to water absorption, decreased stepwise with increasing amounts of crystalline particles. We confirmed that the spectra gave excellent quantitative results, using partial least-squares regression analysis. The results suggest the possibility of using this method for qualitative and quantitative assessments of crystalline drugs in suspension.

  7. Investigating murals with terahertz reflective tomography

    NASA Astrophysics Data System (ADS)

    Yuan, Minjie; Sun, Wenfeng; Wang, Xinke; Wang, Sen; Zhang, Qunxi; Ye, Jiasheng; Zhang, Yan

    2015-08-01

    Terahertz time-domain spectroscopy (THz-TDS) imaging technology has been proposed to be used in the non-invasive detection of murals. THz-TDS images provide structural data of the sample that cannot be obtained with other complementary techniques. In this paper, two types of defects hidden in the plaster used to simulate the cases of defects in the murals, have been investigated by the terahertz reflected time domain spectroscopy imaging system. These preset defects include a leaf slice and a slit built in the plaster. With the terahertz reflective tomography, information about defects has been determined involving the thickness from the surface of sample to the built-in defect, the profile and distribution of the defect. With this THz tomography, different defects with the changes of optical thickness and their relative refractive index have been identified. The application of reflective pulsed terahertz imaging has been extended to the defect detection of the murals.

  8. A quantitative study for determination of sugar concentration using attenuated total reflectance terahertz (ATR-THz) spectroscopy

    NASA Astrophysics Data System (ADS)

    Suhandy, Diding; Suzuki, Tetsuhito; Ogawa, Yuichi; Kondo, Naoshi; Ishihara, Takeshi; Takemoto, Yuichiro

    2011-06-01

    The objective of our research was to use ATR-THz spectroscopy together with chemometric for quantitative study in food analysis. Glucose, fructose and sucrose are main component of sugar both in fresh and processed fruits. The use of spectroscopic-based method for sugar determination is well reported especially using visible, near infrared (NIR) and middle infrared (MIR) spectroscopy. However, the use of terahertz spectroscopy for sugar determination in fruits has not yet been reported. In this work, a quantitative study for sugars determination using attenuated total reflectance terahertz (ATR-THz) spectroscopy was conducted. Each samples of glucose, fructose and sucrose solution with different concentrations were prepared respectively and their absorbance spectra between wavenumber 20 and 450 cm-1 (between 0.6 THz and 13.5 THz) were acquired using a terahertz-based Fourier Transform spectrometer (FARIS-1S, JASCO Co., Japan). This spectrometer was equipped with a high pressure of mercury lamp as light source and a pyroelectric sensor made from deuterated L-alanine triglycine sulfate (DLTGS) as detector. Each spectrum was acquired using 16 cm-1 of resolution and 200 scans for averaging. The spectra of water and sugar solutions were compared and discussed. The results showed that increasing sugar concentration caused decreasing absorbance. The correlation between sugar concentration and its spectra was investigated using multivariate analysis. Calibration models for glucose, fructose and sucrose determination were developed using partial least squares (PLS) regression. The calibration model was evaluated using some parameters such as coefficient of determination (R2), standard error of calibration (SEC), standard error of prediction (SEP), bias between actual and predicted sugar concentration value and ratio prediction to deviation (RPD) parameter. The cross validation method was used to validate each calibration model. It is showed that the use of ATR

  9. Terahertz imaging of composite materials in reflection and transmission mode with a time-domain spectroscopy system

    NASA Astrophysics Data System (ADS)

    Sørgârd, Trygve R.; van Rheenen, Arthur D.; Haakestad, Magnus W.

    2016-02-01

    A fiber-coupled Terahertz time domain spectroscopy (THz-TDS) system based on photoconductive antennas, pumped by a 100-fs fiber laser, has been used to characterize materials in transmission and reflection mode. THz images are acquired by mounting the samples under investigation on an x-y stage, which is stepped through the beam while the transmitted or reflected THz waveform is captured. The samples include a carbon fiber epoxy composite and a sandwich-structured composite panel with an aramid fiber honeycomb core in between two skin layers of fiberglass reinforced plastic. The former has an artificially induced void, and from a comparison of recorded reflected time-domain signals, with and without the void, a simple model for the structure of the composite is proposed that describes the time-domain signals reasonably well.

  10. Terahertz time-domain spectroscopy of biological tissues

    SciTech Connect

    Nazarov, M M; Shkurinov, A P; Kuleshov, E A; Tuchin, V V

    2008-07-31

    Terahertz absorption spectra and dispersion of biologically important substances such as sugar, water, hemoglobin, lipids and tissues are studied. The characteristic absorption lines in the frequency range of a terahertz spectrometer (0.1-3.5 THz) are found. The refraction indices and absorption coefficients of human tooth enamel and dentine are measured. The method of terahertz phase reflection spectroscopy is developed for strongly absorbing substances. Simple and reliable methods of time-resolved terahertz spectroscopy are developed. (biophotonics)

  11. Beating the wavelength limit: three-dimensional imaging of buried subwavelength fractures in sculpture and construction materials by terahertz time-domain reflection spectroscopy.

    PubMed

    Schwerdtfeger, M; Castro-Camus, E; Krügener, K; Viöl, W; Koch, M

    2013-01-20

    We use reflection terahertz spectroscopy to locate and produce three-dimensional images of air gaps between stones that resemble fractures, even of subwavelength thicknesses. This technique is found to be promising tool for sculpture and building damage evaluation as well as structural quality control in other dielectric materials. PMID:23338182

  12. Phase-sensitive terahertz spectroscopy with backward-wave oscillators in reflection mode

    NASA Astrophysics Data System (ADS)

    Pronin, A. V.; Goncharov, Yu. G.; Fischer, T.; Wosnitza, J.

    2009-12-01

    In this article we describe a method which allows accurate measurements of the complex reflection coefficient r̂=|r̂|ṡexp(iφR) of a solid at frequencies of 1-50 cm-1 (30 GHz-1.5 THz). Backward-wave oscillators are used as sources for monochromatic coherent radiation tunable in frequency. The amplitude of the complex reflection (the reflectivity) is measured in a standard way, while the phase shift, introduced by the reflection from the sample surface, is measured using a Michelson interferometer. This method is particular useful for nontransparent samples, where phase-sensitive transmission measurements are not possible. The method requires no Kramers-Kronig transformation in order to extract the sample's electrodynamic properties (such as the complex dielectric function or complex conductivity). Another area of application of this method is the study of magnetic materials with complex dynamic permeabilities different from unity at the measurement frequencies (for example, colossal-magnetoresistance materials and metamaterials). Measuring both the phase-sensitive transmission and the phase-sensitive reflection allows for a straightforward model-independent determination of the dielectric permittivity and magnetic permeability of such materials.

  13. Terahertz Spectroscopy of Biomolecules

    NASA Astrophysics Data System (ADS)

    Korter, Timothy; Plusquellic, David; Hight Walker, Angela; Heilweil, Edwin

    2002-03-01

    A novel, continuous-wave (CW) terahertz spectrometer has been constructed to investigate the flexibility and dynamics of small biological molecules. Hydrogen bonding interactions, torsional vibrations, and conformational changes are expressed in this far-infrared region of the spectrum. Terahertz (THz) radiation (0 - 4 THz or 0 - 133 wavenumber) is generated at the difference frequency of two near-infrared pump lasers by optical heterodyne mixing at the surface of a solid-state photomixer. This spectrometer has been used to probe the low-frequency vibrational modes of several members of the vitamin B-complex including riboflavin, pantothenic acid, and biotin. Interpretation of these unique THz spectra has been aided by low-frequency Raman experiments as well as ab initio predictions for normal mode frequencies and intensities. Instrumental details, vitamin B-complex analyses, and preliminary results for myoglobin and other large biomolecules will be presented.

  14. Probing biological systems with terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Pickwell-MacPherson, Emma; Sun, Yiwen; Parrott, Edward P. J.

    2012-10-01

    Terahertz spectroscopy is able to probe several aspects of biological systems. Most well known is its sensitivity to water due to the strong water absorptions at terahertz frequencies. However an increasing number of studies have shown that it is not just water content that terahertz is sensitive to and that other factors such as tissue structure, molecular arrangement or even temperature can also affect the signal. Examples ranging from breast cancer spectroscopy to antibody protein spectroscopy will be presented and discussed.

  15. Brain tumor imaging of rat fresh tissue using terahertz spectroscopy

    PubMed Central

    Yamaguchi, Sayuri; Fukushi, Yasuko; Kubota, Oichi; Itsuji, Takeaki; Ouchi, Toshihiko; Yamamoto, Seiji

    2016-01-01

    Tumor imaging by terahertz spectroscopy of fresh tissue without dye is demonstrated using samples from a rat glioma model. The complex refractive index spectrum obtained by a reflection terahertz time-domain spectroscopy system can discriminate between normal and tumor tissues. Both the refractive index and absorption coefficient of tumor tissues are higher than those of normal tissues and can be attributed to the higher cell density and water content of the tumor region. The results of this study indicate that terahertz technology is useful for detecting brain tumor tissue. PMID:27456312

  16. Brain tumor imaging of rat fresh tissue using terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Sayuri; Fukushi, Yasuko; Kubota, Oichi; Itsuji, Takeaki; Ouchi, Toshihiko; Yamamoto, Seiji

    2016-07-01

    Tumor imaging by terahertz spectroscopy of fresh tissue without dye is demonstrated using samples from a rat glioma model. The complex refractive index spectrum obtained by a reflection terahertz time-domain spectroscopy system can discriminate between normal and tumor tissues. Both the refractive index and absorption coefficient of tumor tissues are higher than those of normal tissues and can be attributed to the higher cell density and water content of the tumor region. The results of this study indicate that terahertz technology is useful for detecting brain tumor tissue.

  17. Modulated orientation sensitive terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Singh, Rohit

    The energies of protein correlated motions lie in the far infrared or THz frequency range (lambda = 1 cm -- 50 mm, f = 0.03 -- 6 THz). The existence of correlated motions has been confirmed by neutron and inelastic x-ray scattering measurements. These techniques require large sample volumes and specialized facilities, limiting their application to systematic studies of changes in correlated motions with functional state and allosteric interactions. Standard terahertz time domain spectroscopy measurements have shown sensitivity to protein-ligand binding, oxidation state, conformation, temperature and hydration. However, the response is broad, in part from the large vibrational density of states and in part from the dielectric response contribution from surface water and side-chains. As an overall strategy to measure the correlated structural motions in protein, we use anisotropic and birefringent behavior of molecular crystals to develop a new technique called MOSTS (Modulated Orientation Sensitive Terahertz Spectroscopy). We achieve high sensitivity and mode separation, by using single molecular crystal such as sucrose and oxalic acid, and rapid modulation of the relative alignment of the terahertz polarization and the crystal axes by rotating the sample. By locking into the signal at the rotation frequency, we determine the polarization sensitive signal and map out the optically active vibrational resonances. To illustrate the technique, we compare our measured spectra with the calculated, and find a close agreement. We measure dielectric properties of oxalic acid, sucrose and protein crystals and polycarbonate sheet using standard terahertz time domain spectroscopy. We determine the absorbances in oxalic acid and sucrose crystals, using MOSTS technique. We compare the resonances in these two distinct methods. Then, we develop a protein model sample by sticking together two thin plates of sucrose and polycarbonate. We carry out standard THz-TDS and MOSTS

  18. Medical diagnostics using terahertz pulsed spectroscopy

    NASA Astrophysics Data System (ADS)

    Zaytsev, Kirill I.; Kudrin, Konstantin G.; Koroleva, Svetlana A.; Fokina, Irina N.; Volodarskaya, Svetlana I.; Novitskaya, Ekaterina V.; Perov, Artem N.; Karasik, Valeriy E.; Yurchenko, Stanislav O.

    2014-03-01

    The paper contains recent results of studying the ability of human body disease diagnosis with terahertz time-domain spectroscopy. In vitro skin cancer samples (squamous cell carcinoma, epithelioid cell melanoma, infiltrating carcinoma) were studied experimentally with terahertz pulsed spectrometer. The parametrical in vitro images of skin cancers are presented. The ability to make early tooth cariosity diagnosis with terahertz time-domain spectroscopy was also shown experimentally. The results of studying the in vitro tooth samples are presented and discussed.

  19. Terahertz spectroscopy of liver cirrhosis: investigating the origin of contrast

    NASA Astrophysics Data System (ADS)

    Sy, Stanley; Huang, Shengyang; Wang, Yi-Xiang J.; Yu, Jun; Ahuja, Anil T.; Zhang, Yuan-ting; Pickwell-MacPherson, Emma

    2010-12-01

    We have previously demonstrated that terahertz pulsed imaging is able to distinguish between rat tissues from different healthy organs. In this paper we report our measurements of healthy and cirrhotic liver tissues using terahertz reflection spectroscopy. The water content of the fresh tissue samples was also measured in order to investigate the correlations between the terahertz properties, water content, structural changes and cirrhosis. Finally, the samples were fixed in formalin to determine whether water was the sole source of image contrast in this study. We found that the cirrhotic tissue had a higher water content and absorption coefficient than the normal tissue and that even after formalin fixing there were significant differences between the normal and cirrhotic tissues' terahertz properties. Our results show that terahertz pulsed imaging can distinguish between healthy and diseased tissue due to differences in absorption originating from both water content and tissue structure.

  20. Characterization of burn injuries using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Arbab, M. Hassan; Dickey, Trevor C.; Winebrenner, Dale P.; Chen, Antao; Mourad, Pierre D.

    2011-03-01

    The accuracy rates of the clinical assessment techniques used in grading burn injuries remain significantly low for partial thickness burns. In this paper, we present experimental results from terahertz characterization of 2nd and 3rd degree burn wounds induced on a rat model. Reflection measurements were obtained from the surface of both burned and normal skin using pulsed terahertz spectroscopy. Signal processing techniques are described for interpretation of the acquired terahertz waveform and differentiation of burn wounds. Furthermore, the progression of burn injuries is shown by comparison between acute characterization and 72-hours survival studies. While the water content of healthy and desiccated skin has been considered as a source of terahertz signal contrast, it is demonstrated that other biological effects such as formation of post-burn interstitial edema as well as the density of the discrete scattering structures in the skin (such as hair follicles, sweat glands, etc.) play a significant role in the terahertz response of the burn wounds.

  1. A Concealed Barcode Identification System Using Terahertz Time-domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Guan, Yu; Yamamoto, Manabu; Kitazawa, Toshiyuki; Tripathi, Saroj R.; Takeya, Kei; Kawase, Kodo

    2015-03-01

    We present a concealed terahertz barcode/chipless tag to achieve remote identification through an obstructing material using terahertz radiation. We show scanned terahertz reflection spectral images of barcodes concealed by a thick obstacle. A concealed and double- side printed terahertz barcode structure is proposed, and we demonstrate that our design has better performance in definition than a single-side printed barcode using terahertz time-domain spectroscopy. This technique combines the benefits of a chipless tag to read encoded information covered by an optically opaque material with low cost and a simple fabrication process. Simulations are also described, along with an explanation of the principle of the terahertz barcode identification system.

  2. Examining pharmaceuticals using terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Sulovská, Kateřina; Křesálek, Vojtěch

    2015-10-01

    Pharmaceutical trafficking is common issue in countries where they are under stricter dispensing regime with monitoring of users. Most commonly smuggled pharmaceuticals include trade names Paralen Plus, Modafen, Clarinase repetabs, Aspirin complex, etc. These are transported mainly from Eastern Europe (e.g. Poland, Ukraine, Russia) to countries like Czech Republic, which is said to have one of the highest number of methamphetamine producers in Europe. The aim of this paper is to describe the possibility of terahertz spectroscopy utilization as an examining tool to distinguish between pharmaceuticals containing pseudoephedrine compounds and those without it. Selected medicaments for experimental part contain as an active ingredient pseudoephedrine hydrochloride or pseudoephedrine sulphate. Results show a possibility to find a pseudoephedrine compound spectra in samples according to previously computed and experimentally found ones, and point out that spectra of same brand names pills may vary according to their expiration date, batch, and amount of absorbed water vapours from ambience. Mislead spectrum also occurs during experimental work in a sample without chosen active ingredient, which shows persistent minor inconveniences of terahertz spectroscopy. All measurement were done on the TPS Spectra 3000 instrument.

  3. Terahertz homodyne self-mixing transmission spectroscopy

    SciTech Connect

    Mohr, Till Breuer, Stefan; Blömer, Dominik; Patel, Sanketkumar; Schlosser, Malte; Birkl, Gerhard; Elsäßer, Wolfgang; Simonetta, Marcello; Deninger, Anselm; Giuliani, Guido

    2015-02-09

    A compact homodyne self-mixing terahertz spectroscopy concept is experimentally investigated and confirmed by calculations. This method provides amplitude and phase information of the terahertz radiation emitted by a photoconductive antenna in a transmission experiment where a rotating chopper wheel serves as a feedback mirror. As a proof-of-principle experiment the frequency-dependent refractive index of Teflon is measured.

  4. Terahertz spectroscopy of two-dimensional subwavelength plasmonic structures

    SciTech Connect

    Azad, Abul K; Chen, Houtong; Taylor, Antoinette; O' Hara, John F; Han, Jiaguang; Lu, Xinchao; Zhang, Weili

    2009-01-01

    The fascinating properties of plasmonic structures have had significant impact on the development of next generation ultracompact photonic and optoelectronic components. We study two-dimensional plasmonic structures functioning at terahertz frequencies. Resonant terahertz response due to surface plasmons and dipole localized surface plasmons were investigated by the state-of-the-art terahertz time domain spectroscopy (THz-TDS) using both transmission and reflection configurations. Extraordinary terahertz transmission was demonstrated through the subwavelength metallic hole arrays made from good conducting metals as well as poor metals. Metallic arrays m!lde from Pb, generally a poor metal, and having optically thin thicknesses less than one-third of a skin depth also contributed in enhanced THz transmission. A direct transition of a surface plasmon resonance from a photonic crystal minimum was observed in a photo-doped semiconductor array. Electrical controls of the surface plasmon resonances by hybridization of the Schottkey diode between the metallic grating and the semiconductor substrate are investigated as a function of the applied reverse bias. In addition, we have demonstrated photo-induced creation and annihilation of surface plasmons with appropriate semiconductors at room temperature. According to the Fano model, the transmission properties are characterized by two essential contributions: resonant excitation of surface plasmons and nonresonant direct transmission. Such plasmonic structures may find fascinating applications in terahertz imaging, biomedical sensing, subwavelength terahertz spectroscopy, tunable filters, and integrated terahertz devices.

  5. Terahertz spectroscopy of plasmonic fractals.

    PubMed

    Agrawal, A; Matsui, T; Zhu, W; Nahata, A; Vardeny, Z V

    2009-03-20

    We use terahertz time-domain spectroscopy to study the transmission properties of metallic films perforated with aperture arrays having deterministic or stochastic fractal morphologies ("plasmonic fractals"), and compare them with random aperture arrays. All of the measured plasmonic fractals show transmission resonances and antiresonances at frequencies that correspond to prominent features in their structure factors in k space. However, in sharp contrast to periodic aperture arrays, the resonant transmission enhancement decreases with increasing array size. This property is explained using a density-density correlation function, and is utilized for determining the underlying fractal dimensionality, D(<2). Furthermore, a sum rule for the transmission resonances and antiresonances in plasmonic fractals relative to the transmission of the corresponding random aperture arrays is obtained, and is shown to be universal.

  6. Research on time-resolved terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Deng, Yuqiang; Sun, Qing; Liu, Feng; Wang, Changlei; Xing, Qirong

    2010-10-01

    We have built a set of terahertz time-domain spectroscopy system using electro-optic crystals. Conventional terahertz time-domain spectroscopy based on Fourier-transform for spectra analysis, which mixes the frequency components of the entire temporal terahertz waveform in one frequency domain; therefore, it yields different terahertz spectra from a same terahertz pulse with different scanning lengths. We introduce a new technique for the joint time-frequency analysis of terahertz time-domain spectroscopy based on wavelet-transform technique. With this technique, the frequency components in different time locations are clearly exhibited on a two-dimensional plane; therefore, the noise in the pulse tail cannot affect the frequency in the main pulse. This technique clearly separates the frequency of terahertz from that of its echo in the time domain; therefore, the interference spectrum occur in Fourier-transform is naturally removed. By varying the shape of analysis wavelet, high time resolution and high frequency resolution are easily obtained. The absorption coefficients of envelope, plastic, foam and cotton have been measured with the wavelet technique.

  7. Terahertz correlation spectroscopy infers particle velocity and rheological properties.

    PubMed

    Rees, Eric J; Su, Ke; Zeitler, Axel

    2016-07-15

    Correlation spectroscopy is an analytical technique that can identify the residence time of reflective or fluorescent particles in a measurement spot, allowing particle velocity or diffusion to be inferred. We show that the technique can be applied to data measured with a time-domain terahertz sensor. The speed of reflectors such as silica ballotini or bubbles can thus be measured in fluid samples. Time-domain terahertz sensors can therefore be used, for the first time, to measure rheological properties of optically opaque fluids that contain entrained reflectors, such as polyethylene beads. PMID:27420517

  8. Extending applicability of terahertz spectroscopy for biosensing

    NASA Astrophysics Data System (ADS)

    Parthasarathy, Ramakrishnan

    Terahertz (THz) vibrational resonance spectroscopy has recently emerged as a promising technique for fingerprinting biological molecules. Absorption spectra in this frequency range (0.1-10 THz) reflect molecular internal vibrations involving the weakest hydrogen bonds and/or non-bonded interactions, which are species specific. Of prime importance is improving detection sensitivity of molecules with low absorption characteristics in the THz gap. Also of importance is the characterization of biological molecules in the THz gap (10-25 cm-1) by physical parameters (refractive index and absorption coefficient) rather than sample dependent parameters (transmission, reflection) and extending spectroscopy to the low THz range where remote sensing is most viable. To address the sensitivity issue, it is shown that periodic arrays of rectangular slots with subwavelength width provide for local electromagnetic field enhancements due to edge effects in the low frequency range of interest, 10-25 cm-1 (300-750 GHz). Periodic structures of Au, doped Si and InSb were studied. InSb is confirmed to offer the highest results with the local power enhancements on the order of 1100 at frequency 14 cm -1. InSb and Si have large skin depths in the frequency range of interest and so the analysis of their structures was done through the Fourier expansion method of field diffracted from gratings. Au however has small skin depths at these frequencies compared to the thickness. Surface impedance boundary conditions were employed to model the Au structure, for which the Fourier expansion method was unsuitable owing to the huge magnitude of Au permittivity. The applications possibly include development of novel bio-sensors, with the strongly enhanced local electromagnetic fields leading to increased detection sensitivity, and monitoring biophysical processes such as DNA denaturation. Transmission and reflection data from parallel, independent experiments are utilized in the Interference

  9. Terahertz wave reflective sensing and imaging

    NASA Astrophysics Data System (ADS)

    Zhong, Hua

    Sensing and imaging technologies using terahertz (THz) radiation have found diverse applications as they approach maturity. Since the burgeoning of this technique in the 1990's, many THz sensing and imaging investigations have been designed and conducted in transmission geometry, which provides sufficient phase and amplitude contrast for the study of the spectral properties of targets in the THz domain. Driven by rising expectations that THz technology will be a potential candidate in the next generation of security screening, remote sensing, biomedical imaging and non-destructive testing (NDT), most THz sensing and imaging modalities are being extended to reflection geometry, which offers unique and adaptive solutions, and multi-dimensional information in many real scenarios. This thesis takes an application-focused approach to the advancement of THz wave reflective sensing and imaging systems: The absorption signature of the explosive material hexahydro-1,3,5-trinitro-1,3,5triazine (RDX) is measured at 30 m---the longest standoff distance so far attained by THz time-domain spectroscopy (THz-TDS). The standoff distance sensing ability of THz-TDS is investigated along with discussions specifying the influences of a variety of factors such as propagation distance, water vapor absorption and collection efficiency. Highly directional THz radiation from four-wave mixing in laser-induced air plasmas is first observed and measured, which provides a potential solution for the atmospheric absorption effect in standoff THz sensing. The simulations of the beam profiles also illuminate the underlying physics behind the interaction of the optical beam with the plasma. THz wave reflective spectroscopic focal-plane imaging is realized the first time. Absorption features of some explosives and related compounds (ERCs) and biochemical materials are identified by using adaptive feature extraction method. Good classification results using multiple pattern recognition methods are

  10. High frequency resolution terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Sangala, Bagvanth Reddy

    2013-12-01

    A new method for the high frequency resolution terahertz time-domain spectroscopy is developed based on the characteristic matrix method. This method is useful for studying planar samples or stack of planar samples. The terahertz radiation was generated by optical rectification in a ZnTe crystal and detected by another ZnTe crystal via electro-optic sampling method. In this new characteristic matrix based method, the spectra of the sample and reference waveforms will be modeled by using characteristic matrices. We applied this new method to measure the optical constants of air. The terahertz transmission through the layered systems air-Teflon-air-Quartz-air and Nitrogen gas-Teflon-Nitrogen gas-Quartz-Nitrogen gas was modeled by the characteristic matrix method. A transmission coefficient is derived from these models which was optimized to fit the experimental transmission coefficient to extract the optical constants of air. The optimization of an error function involving the experimental complex transmission coefficient and the theoretical transmission coefficient was performed using patternsearch algorithm of MATLAB. Since this method takes account of the echo waveforms due to reflections in the layered samples, this method allows analysis of longer time-domain waveforms giving rise to very high frequency resolution in the frequency-domain. We have presented the high frequency resolution terahertz time-domain spectroscopy of air and compared the results with the literature values. We have also fitted the complex susceptibility of air to the Lorentzian and Gaussian functions to extract the linewidths.

  11. Metamaterial radiation from attenuated total reflection at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Ramani, Suchitra

    The focus of this research was to explore the behavior of two-dimensional planar metamaterials or metafilms and understand the various excitation schemes for application of metafilms to Terahertz-Attenuated Total Reflection spectroscopy (THz-ATR). A standard THz time domain spectroscopy system based on photoconductive switches was modified to implement the ATR technique. Finite metamaterial arrays with varying singly- split ring resonator sizes were excited in the Kretschmann ATR configuration using finite sized terahertz beams. Numerical approaches using commercial software were looked into to explain the experimental observations. Various theoretical models were used to explain the observed phenomena. The ATR measurements showed an unexpected strengthening of the resonance when the metafilm sample was illuminated near the edge. This phenomenon referred to in this study as "the anomalous edge enhancement" was observed strongly in metafilms with closely spaced rings. A re-radiation signal was observed across the total internal reflection barrier where no signal is expected. It consisted of two peaks one at the fundamental metamaterial resonance and the second peak was due to the periodicity of the metafilm array. The anomalous behavior seen in the ATR measurements is attributed to the edge currents at the boundary of the metafilm array giving rise to this re-radiation signal. Results from analytic treatments based on Floquet method and method of moments were able to qualitatively model the measurements. The observed re-radiation signal is a potential loss mechanism that could impact observations from commonly used transmission measurements on metamaterials.

  12. A promising diagnostic method: Terahertz pulsed imaging and spectroscopy

    PubMed Central

    Sun, Yiwen; Sy, Ming Yiu; Wang, Yi-Xiang J; Ahuja, Anil T; Zhang, Yuan-Ting; Pickwell-MacPherson, Emma

    2011-01-01

    The terahertz band lies between the microwave and infrared regions of the electromagnetic spectrum. This radiation has very low photon energy and thus it does not pose any ionization hazard for biological tissues. It is strongly attenuated by water and very sensitive to water content. Unique absorption spectra due to intermolecular vibrations in this region have been found in different biological materials. These unique features make terahertz imaging very attractive for medical applications in order to provide complimentary information to existing imaging techniques. There has been an increasing interest in terahertz imaging and spectroscopy of biologically related applications within the last few years and more and more terahertz spectra are being reported. This paper introduces terahertz technology and provides a short review of recent advances in terahertz imaging and spectroscopy techniques, and a number of applications such as molecular spectroscopy, tissue characterization and skin imaging are discussed. PMID:21512652

  13. Terahertz spectroscopy of pigmentary skin nevi in vivo

    NASA Astrophysics Data System (ADS)

    Zaitsev, K. I.; Chernomyrdin, N. V.; Kudrin, K. G.; Reshetov, I. V.; Yurchenko, S. O.

    2015-09-01

    Pigmentary skin nevi are studied in vivo using terahertz pulsed spectroscopy. Dielectric parameters of healthy skin and dysplastic and nondysplastic nevi are reconstructed and analyzed. The fact that complex permittivities of the samples substantially differ in the terahertz spectral range can be used for early noninvasive diagnostics of dysplastic nevi, which are precursors of melanoma (the most dangerous skin cancer). A method is proposed to identify various dysplastic and nondysplastic nevi using the analysis of terahertz dielectric characteristics. It is demonstrated that terahertz pulsed spectroscopy is promising for early noninvasive diagnostics of dysplastic nevi and melanomas of the skin.

  14. Note: Single-shot time-domain spectroscopy and spatial profiling of terahertz pulses from intense laser systems.

    PubMed

    Zhang, T J; Jin, Z; Wakamatsu, S; Hosokai, T; Yugami, N; Kodama, R

    2016-06-01

    Single-shot terahertz time-domain spectroscopy is presented with directly encoded spatial resolution. A single reflective echelon and multiple semi-cylindrical lenses are used to obtain both the temporal waveform and the spatial distribution of the terahertz field. This system can be used to rapidly characterize terahertz pulses generated by high power pulsed laser systems, which themselves suffer from large pulse energy and spectrum fluctuations. PMID:27370502

  15. Biomedical Applications of Terahertz Spectroscopy and Imaging.

    PubMed

    Yang, Xiang; Zhao, Xiang; Yang, Ke; Liu, Yueping; Liu, Yu; Fu, Weiling; Luo, Yang

    2016-10-01

    Terahertz (THz=10(12)Hz) radiation has attracted wide attention for its unprecedented sensing ability and its noninvasive and nonionizing properties. Tremendous strides in THz instrumentation have prompted impressive breakthroughs in THz biomedical research. Here, we review the current state of THz spectroscopy and imaging in various biomedical applications ranging from biomolecules, including DNA/RNA, amino acids/peptides, proteins, and carbohydrates, to cells and tissues. We also address the potential biological effects of THz radiation during its biological applications and propose future prospects for this cutting-edge technology.

  16. Terahertz and mid-infrared reflectance of epitaxial graphene

    PubMed Central

    Santos, Cristiane N.; Joucken, Frédéric; De Sousa Meneses, Domingos; Echegut, Patrick; Campos-Delgado, Jessica; Louette, Pierre; Raskin, Jean-Pierre; Hackens, Benoit

    2016-01-01

    Graphene has emerged as a promising material for infrared (IR) photodetectors and plasmonics. In this context, wafer scale epitaxial graphene on SiC is of great interest in a variety of applications in optics and nanoelectronics. Here we present IR reflectance spectroscopy of graphene grown epitaxially on the C-face of 6H-SiC over a broad optical range, from terahertz (THz) to mid-infrared (MIR). Contrary to the transmittance, reflectance measurements are not hampered by the transmission window of the substrate, and in particular by the SiC Reststrahlen band in the MIR. This allows us to present IR reflectance data exhibiting a continuous evolution from the regime of intraband to interband charge carrier transitions. A consistent and simultaneous analysis of the contributions from both transitions to the optical response yields precise information on the carrier dynamics and the number of layers. The properties of the graphene layers derived from IR reflection spectroscopy are corroborated by other techniques (micro-Raman and X-ray photoelectron spectroscopies, transport measurements). Moreover, we also present MIR microscopy mapping, showing that spatially-resolved information can be gathered, giving indications on the sample homogeneity. Our work paves the way for a still scarcely explored field of epitaxial graphene-based THz and MIR optical devices. PMID:27102827

  17. Terahertz and mid-infrared reflectance of epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Santos, Cristiane N.; Joucken, Frédéric; de Sousa Meneses, Domingos; Echegut, Patrick; Campos-Delgado, Jessica; Louette, Pierre; Raskin, Jean-Pierre; Hackens, Benoit

    2016-04-01

    Graphene has emerged as a promising material for infrared (IR) photodetectors and plasmonics. In this context, wafer scale epitaxial graphene on SiC is of great interest in a variety of applications in optics and nanoelectronics. Here we present IR reflectance spectroscopy of graphene grown epitaxially on the C-face of 6H-SiC over a broad optical range, from terahertz (THz) to mid-infrared (MIR). Contrary to the transmittance, reflectance measurements are not hampered by the transmission window of the substrate, and in particular by the SiC Reststrahlen band in the MIR. This allows us to present IR reflectance data exhibiting a continuous evolution from the regime of intraband to interband charge carrier transitions. A consistent and simultaneous analysis of the contributions from both transitions to the optical response yields precise information on the carrier dynamics and the number of layers. The properties of the graphene layers derived from IR reflection spectroscopy are corroborated by other techniques (micro-Raman and X-ray photoelectron spectroscopies, transport measurements). Moreover, we also present MIR microscopy mapping, showing that spatially-resolved information can be gathered, giving indications on the sample homogeneity. Our work paves the way for a still scarcely explored field of epitaxial graphene-based THz and MIR optical devices.

  18. Moisture detection in composites by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Malinowski, Paweł; Pałka, Norbert; Opoka, Szymon; Wandowski, Tomasz; Ostachowicz, Wiesław

    2015-07-01

    The application of Glass Fibre Reinforced Polymers (GFRP) in many branches of industry has been increasing steadily. Many research works focus on damage identification for structures made out of such materials. However, not only delaminations, cracks or other damage can have a negative influence of GFRP parts performance. Previous research proved that fluid absorption influences the mechanical performance of composites. GFRP parts can be contaminated by moisture or release agent during manufacturing, while fuel, hydraulic fluid and moisture ingression into the composite can be the in-service treats. In the reported research authors focus on moisture detection. There are numerous sources of moisture such as post manufacturing NDT inspection with ultrasonics coupled by water or exposition to moisture during transportation and in service. An NDT tool used for the research is a terahertz (THz) spectrometer. The device uses an electromagnetic radiation in the terahertz range (0.1-3 THz) and allows for reflection and transmission measurements. The spectrometer is equipped with moving table that allows for XY scanning of large objects such as GFRP panels. In the conducted research refractive indices were experimentally extracted from the materials of interest (water and GFRP). Time signals as well as C-scans were analysed for samples with moisture contamination. In order to be sure that the observed effects are related to moisture contamination reference measurements were conducted. The obtained results showed that the THz NDT technique can detect moisture hidden under a GFRP with multiple layers.

  19. [Study on terahertz spectroscopy of Hotan jade].

    PubMed

    Maimaitiming; Ainiwaer; Xiong, Wei; Guo, Xue-jiao; Shen, Jing-ling

    2010-10-01

    Terahertz time-domain spectroscopy (THz-TDS) technique has a wide range of applications including illicit drugs and explosive detection, and organic molecules recognition. In the present paper, the spectral features of three kinds of Hotan jade were studied experimentally by THz-TDS technique and the characteristic absorption spectra and refractive index were obtained in the range of 0.2 to 2.6 THz. The experimental results show that different samples have different absorption characters, and the refractive index is 2.4-2.7 in the range of 0.2-2.6 THz. The results indicate that it is feasible to apply THz-TDS technique to identification of Hotan jade, which provides a new approach to the nondestructive examination of Hotan jade.

  20. Terahertz Spectroscopy of Biotin and Pyridoxine.

    PubMed

    Jiang, Ling; Li, Miao; Li, Chun; Sun Hai-jun; Xu, Li; Liu, Yun-fei

    2015-10-01

    Terahertz (THz) absorption spectra of the biotin and pyridoxine were studied using Fourier transform infrared spectroscopy (FTIR) at room temperature. These spectra exhibit enhanced absorption in THz range because of strong intramolecular and intermolecular vibration modes. In the experiment, the samples were mixed with high density polyethylene powder, which was used as spectrophotometric grid. The absorption spectra show worse consistency at higher frequencies for the high ratio of the samples to polyethylene. It indicates that the absorbance of the biotin and pyridoxine increased with frequency. Molecular vibrational spectral calculations based on density functional theory (DFT) show strong correlation with the experiment. We investigated the absorption spectra of isolated molecules (single molecule, two molecules, three molecules) and unit cell of crystal to clarify the mechanism of the spectra change due to intramolecular and intermolecular vibration and rotation.

  1. New Development for Terahertz Spectroscopy in Lille

    NASA Astrophysics Data System (ADS)

    Margulès, L.; Motiyenko, R. A.; Alekseev, E. A.

    2014-06-01

    Terahertz domain is particularly interesting for spectroscopy of atmospheric species since the rotational spectra of light molecules like water or methanol have their absorption maximum in this range. Up to few years ago the source commonly used in terahertz domain were the backward wave oscillators. These radiation sources provide relatively high output power (several milliwatts) in the frequency range up to 1.2 THz However the BWOs are not easy to handle: they need high voltage supply (2 - 6 kV), water cooling, magnetic field up to 1 Tesla, and a phase locked loop to give accurate frequency measurements. With the arrival of telescopes working in the THz range, great improvements were achieved in the development of solid state devices based on Schottky diodes. The new spectrometer in Lille take advantage of this development and is now based on a frequency multiplication chain using these devices. The spectrometer covers more than 80% of the frequency range 0.05 - 1.5 THz, and we need about 150 hours to record the spectra in this range with high resolution. We will present two short-term projects for the spectrometer. The first one is to increase the frequency range up to 1.9 THz in order to have the full coverage of Herschel telescope. The second one is to speed up the experimental setup. Recently we have shown that one can obtain high resolution and high precision broadband spectra with a high recording rate using a DDS synthesizer in the phase-locked loop of a BWO1. Such fast-scan spectroscopy is particularly interesting for unstable species2,3. Our project is to couple a DDS synthesizer with a 10 - 20 GHz reference synthesizer and a frequency multiplication chain to obtain fast-scan solid state spectrometer. This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI. This work was also done under Ukrainian-French CNRS-PICS 6051 project

  2. Terahertz Spectroscopy of Biochars and Related Aromatic Compounds

    NASA Astrophysics Data System (ADS)

    Lepodise, L. M.; Horvat, J.; Lewis, R. A.

    2016-07-01

    A recent application of terahertz spectroscopy is to biochar, the agricultural charcoal produced by pyrolysis of various organic materials. Biochars simultaneously improve soil fertility and assist in carbon sequestration. Terahertz spectroscopy allows different biochars to be distinguished. However, the origin of the absorption features observed has not been clear. Given that biochar-based fertilizers are rich in aromatic compounds, we have investigated simple aromatic compounds as an approach to unravelling the complex biochar spectrum.

  3. Optical characteristics of pesticides measured by terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Kyu; Kim, Giyoung; Son, Joo-Hiuk

    2015-07-01

    In this study, we measured the optical characteristics of pesticides by terahertz time-domain spectroscopy. Pesticide samples were prepared as pellets that were mixed with polyethylene powder and placed in the center of the path of a terahertz electromagnetic (EM) wave in the spectroscopy system. The absorbance of each sample showed obvious differences in absorption peaks. From this result, we showed that these pesticide products had resonance modes in the terahertz range, and this method can be used to make a sensor that is able to measure low concentrations of pesticides in farm produce.

  4. Papyrus imaging with terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Labaune, J.; Jackson, J. B.; Pagès-Camagna, S.; Duling, I. N.; Menu, M.; Mourou, G. A.

    2010-09-01

    Terahertz time domain spectroscopic imaging (THz-TDSI) is a non-ionizing, non-contact and non-destructive measurement technique that has been recently utilized to study cultural heritage artifacts. We will present this technique and the results of non-contact measurements of papyrus texts, including images of hidden papyri. Inks for modern papyrus specimens were prepared using the historical binder, Arabic gum, and two common pigments used to write ancient texts, carbon black and red ochre. The samples were scanned in reflection at normal incidence with a pulse with a spectral range between 0.1 and 1.5 THz. Temporal analysis of the signals provides the depths of the layers, and their frequency spectra give information about the inks.

  5. Coherent Nonlinear Terahertz Spectroscopy of Halomethane Liquids

    NASA Astrophysics Data System (ADS)

    Finneran, Ian A.; Welsch, Ralph; Allodi, Marco A.; Miller, Thomas F., III; Blake, Geoffrey

    2016-06-01

    The low-energy terahertz motions of liquids greatly influence their behavior, but are not fully understood. Here, we present results from a recently developed heterodyne-detected Terahertz Kerr Effect (TKE) spectrometer, using an intense picosecond terahertz pump pulse, followed by a weak near-infrared femtosecond probe pulse. In the responses of several halomethane liquids, we find evidence for terahertz intramolecular vibrational coupling and the excitation of intermolecular motions. The experimental results are further supported by reduced density matrix and molecular dynamics simulations. With modest improvements in sensitivity, we expect this technique to be applicable to hydrogen-bonded liquids and amorphous solids.

  6. Terahertz spectroscopy: Its future role in medical diagnoses

    NASA Astrophysics Data System (ADS)

    Parrott, Edward Philip John; Sun, Yiwen; Pickwell-MacPherson, Emma

    2011-12-01

    Over the past two decades, terahertz radiation has received a lot of interest due to advances in emission and detection technologies in the late 1980s and early 1990s which allowed the construction of coherent source/detection regimes. This paper focuses on reviewing the use of terahertz radiation in the investigation and understanding of biological systems and medical diagnosis. In particular, research on terahertz spectroscopy of biomolecules, from amino acids to proteins is presented, and examples of potential medical applications are discussed.

  7. Terahertz and infrared spectroscopy of gated large-area graphene.

    PubMed

    Ren, Lei; Zhang, Qi; Yao, Jun; Sun, Zhengzong; Kaneko, Ryosuke; Yan, Zheng; Nanot, Sébastien; Jin, Zhong; Kawayama, Iwao; Tonouchi, Masayoshi; Tour, James M; Kono, Junichiro

    2012-07-11

    We have fabricated a centimeter-size single-layer graphene device with a gate electrode, which can modulate the transmission of terahertz and infrared waves. Using time-domain terahertz spectroscopy and Fourier-transform infrared spectroscopy in a wide frequency range (10-10 000 cm(-1)), we measured the dynamic conductivity change induced by electrical gating and thermal annealing. Both methods were able to effectively tune the Fermi energy, E(F), which in turn modified the Drude-like intraband absorption in the terahertz as well as the "2E(F) onset" for interband absorption in the mid-infrared. These results not only provide fundamental insight into the electromagnetic response of Dirac fermions in graphene but also demonstrate the key functionalities of large-area graphene devices that are desired for components in terahertz and infrared optoelectronics. PMID:22663563

  8. Terahertz reflection response measurement using a phonon polariton wave

    NASA Astrophysics Data System (ADS)

    Inoue, Hayato; Katayama, Kenji; Shen, Qing; Toyoda, Taro; Nelson, Keith A.

    2009-03-01

    We developed a new technique for the measurement of terahertz reflection responses utilizing a propagating phonon polariton wave. Frequency tunable phonon polariton waves were generated by the recently developed continuously variable spatial frequency transient grating method [K. Katayama, H. Inoue, H. Sugiya, Q. Shen, T. Taro, and K. A. Nelson, Appl. Phys. Lett. 92, 031906 (2008)]. The phonon polariton wave traveled in a ferroelectric crystal in an in-plane direction with an inclined angle of 26°, and the wave reflected at the crystal edge where a sample was positioned. The reflected polariton wave was detected by the same method as that used for the generation of the polariton waves. By comparing the reflection intensities in the presence and absence of the sample, reflectivity of the polariton wave was calculated, and the refractive index and absorption in the terahertz region were obtained.

  9. Terahertz vibrational absorption spectroscopy using microstrip-line waveguides

    NASA Astrophysics Data System (ADS)

    Byrne, M. B.; Cunningham, J.; Tych, K.; Burnett, A. D.; Stringer, M. R.; Wood, C. D.; Dazhang, L.; Lachab, M.; Linfield, E. H.; Davies, A. G.

    2008-11-01

    We demonstrate that terahertz microstrip-line waveguides can be used to measure absorption spectra of polycrystalline materials with a high frequency resolution (˜2 GHz) and with a spatial resolution that is determined by the microstrip-line dimensions, rather than the free-space wavelength. The evanescent terahertz-bandwidth electric field extending above the microstrip line interacts with, and is modified by, overlaid dielectric samples, thus enabling the characteristic vibrational absorption resonances in the sample to be probed. As an example, the terahertz absorption spectrum of polycrystalline lactose monohydrate was investigated; the lowest lying mode was observed at 534(±2) GHz, in excellent agreement with free-space measurements. This microstrip technique offers both a higher spatial and frequency resolution than free-space terahertz time-domain spectroscopy and requires no contact between the waveguide and sample.

  10. Measurement and modeling of rough surface effects on terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Henry, S. C.; Schecklman, S.; Kniffin, G. P.; Zurk, L. M.; Chen, A.

    2010-02-01

    Recent improvements in sensing technology have driven new research areas within the terahertz (THz) portion of the electromagnetic (EM) spectrum. While there are several promising THz applications, several outstanding technical challenges need to be addressed before robust systems can be deployed. A particularly compelling application is the potential use of THz reflection spectroscopy for stand-off detection of drugs and explosives. A primary challenge for this application is to have sufficient signal-to-noise ratio (SNR) to allow spectroscopic identification of the target material, and surface roughness can have an impact on identification. However, scattering from a rough surface may be observed at all angles, suggesting diffuse returns can be used in robust imaging of non-cooperative targets. Furthermore, the scattering physics can also distort the reflection spectra, complicating classification algorithms. In this work, rough surface scattering effects were first isolated by measuring diffuse scattering for gold-coated sandpaper of varying roughness. Secondly, we measured scattering returns from a rough sample with a spectral signature, namely α-lactose monohydrate mixed with Teflon and pressed with sandpaper to introduce controlled roughness. For both the specular and diffuse reflection measurements, the application of traditional spectroscopy techniques provided the ability to resolve the 0.54 THz absorption peak. These results are compared with results from a smooth surface. Implications of the results on the ability to detect explosives with THz reflection spectroscopy are presented and discussed. In addition, the Small Perturbation Method (SPM) is employed to predict backscatter from lactose with a small amount of roughness.

  11. Terahertz reflection imaging using Kirchhoff migration.

    PubMed

    Dorney, T D; Johnson, J L; Van Rudd, J; Baraniuk, R G; Symes, W W; Mittleman, D M

    2001-10-01

    We describe a new imaging method that uses single-cycle pulses of terahertz (THz) radiation. This technique emulates data-collection and image-processing procedures developed for geophysical prospecting and is made possible by the availability of fiber-coupled THz receiver antennas. We use a simple migration procedure to solve the inverse problem; this permits us to reconstruct the location and shape of targets. These results demonstrate the feasibility of the THz system as a test-bed for the exploration of new seismic processing methods involving complex model systems. PMID:18049652

  12. Terahertz wave reference-free transmission spectroscopy of aminophenol

    NASA Astrophysics Data System (ADS)

    Deng, Chao; Zhong, Hua; Zhang, Liangliang; Zhang, Cunlin

    2008-12-01

    We present a reference-free transmission spectroscopy of two kinds of aminophenol (Tyrosine and Phenylalanine) using terahertz time domain spectroscopy (THz-TDS). The THz band, which refers to the spectral region between 0.1 to 10 THz, offers a plethora of fingerprints of many chemical and biological materials. Within the past few years, efforts have been focused on exploiting the broadband nature of the THz time domain spectroscopy (THz-TDS) system for material identification and characterization. The conventional spectroscopic sensing method involves measuring both the terahertz signal carrying the sample information and a reference terahertz signal. In transmission geometry measurement, the absorption peaks of the sample material are found by taking the logarithm of the power spectrum of the transmitted signal beam divided by a reference power spectrum. In this work, we propose a reference-free approach to extract the absorption feature in THz transmission spectroscopy. The samples are identified by their absorption peaks extracted from the negative first-order derivative of the sample signal phase divided by the frequency. Unlike in conventional transmission spectroscopy measurement, in this method, the amplitude spectrum of the terahertz signal is not considered at all. Instead, the absorption features are extracted exclusively from the phase information by taking advantage of the almost-linear phase spectrum of terahertz pulses and the correlation between dispersion and absorption. It is also noted that the spectral phase of the terahertz pulse can be determined with far greater accuracy than the amplitude, which makes this method even more favorable. We measured two kinds of aminophenol (Tyrosine and Phenylalanine), and calculated the absorbance spectrum of each by both methods: taking the ratio between the power spectra of the sample signal and the reference signal and the reference-free phase spectrum of each material. The agreement between the positions

  13. Terahertz quantum well photodetectors with reflection-grating couplers

    SciTech Connect

    Zhang, R.; Fu, Z. L.; Gu, L. L.; Guo, X. G.; Cao, J. C.

    2014-12-08

    The design, fabrication, and characterization of terahertz (THz) quantum well photodetectors with one-dimensional reflection-grating coupler are presented. It is found that the reflection gratings could effectively couple the THz waves normally incident to the device. Compared with the 45-degree facet sample, the peak responsivity of this grating-coupled detector is enhanced by over 20%. The effects of the gratings on the photocurrent spectra are also analyzed.

  14. Modern applications of terahertz emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Harrel, Shayne Matthew

    Terahertz (THz) emission spectroscopy (TES) is newly developed experimental technique capable of measuring ultrafast dynamics in a variety of systems. Unlike pump-probe spectroscopies where the signals are obtained indirectly, the THz waveform emitted by the dynamical process serves as the signal field. Information about processes involving a time-dependent magnetization, polarization or current is obtained using TES. The detection scheme is polarization sensitive and allows the direction of the dynamical event to be recovered. The role of solvation on intramolecular charge transfer in DMANS (4-(dimethylamino)-4'-nitrostilbene) is studied using TES in three solvents: benzene, toluene, and 1,3-dichlorobenzene. These solvents have similar molecular structures but different polarities and dielectric constants. The charge transfer dynamics are found to depend on the solvent. A secondary feature in the THz emission appearing 4-6 Ps after the main pulse provides evidence that DMANS may undergo a twisted intramolecular charge transfer state (TICT) upon photoexcitation. The ultrafast magnetization dynamics of polycrystalline Ni and single Fe films ranging in thickness from 5 nm to 60 nm are reported using TES. For samples thicker than the visible optical skin depth, (˜10 nm for Ni and ˜27 nm for Fe), the emission is easily interpreted using Lenz's law. For films thinner than visible optical skin depth, the emission patterns are qualitatively different. These results suggest that there are two generation mechanisms at work: one that arises purely from bulk demagnetization in the thick sample limit and another that is the result of difference frequency generation enhanced by the magnetized surface. A comparative study of the magnetization dynamics of a 40 nm Ni and 40 Fe film shows that the magnetization recovers faster in Fe than in Ni. The dependence of optical rectification and shift currents in unbiased GaAs (111) is reported using TES. It is found that the dependence

  15. Squeezing terahertz light into nanovolumes: nanoantenna enhanced terahertz spectroscopy (NETS) of semiconductor quantum dots.

    PubMed

    Toma, Andrea; Tuccio, Salvatore; Prato, Mirko; De Donato, Francesco; Perucchi, Andrea; Di Pietro, Paola; Marras, Sergio; Liberale, Carlo; Proietti Zaccaria, Remo; De Angelis, Francesco; Manna, Liberato; Lupi, Stefano; Di Fabrizio, Enzo; Razzari, Luca

    2015-01-14

    Terahertz spectroscopy has vast potentialities in sensing a broad range of elementary excitations (e.g., collective vibrations of molecules, phonons, excitons, etc.). However, the large wavelength associated with terahertz radiation (about 300 μm at 1 THz) severely hinders its interaction with nano-objects, such as nanoparticles, nanorods, nanotubes, and large molecules of biological relevance, practically limiting terahertz studies to macroscopic ensembles of these compounds, in the form of thick pellets of crystallized molecules or highly concentrated solutions of nanomaterials. Here we show that chains of terahertz dipole nanoantennas spaced by nanogaps of 20 nm allow retrieving the spectroscopic signature of a monolayer of cadmium selenide quantum dots, a significant portion of the signal arising from the dots located within the antenna nanocavities. A Fano-like interference between the fundamental antenna mode and the phonon resonance of the quantum dots is observed, accompanied by an absorption enhancement factor greater than one million. NETS can find immediate applications in terahertz spectroscopic studies of nanocrystals and molecules at extremely low concentrations. Furthermore, it shows a practicable route toward the characterization of individual nano-objects at these frequencies.

  16. Identify paraffin-embedded brain glioma using terahertz pulsed spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Ze-ren; Meng, Kun; Chen, Tu-nan; Chen, Tao; Zhu, Li-guo; Liu, Qiao; Li, Zhao; Li, Fei; Zhong, Sen-cheng; Feng, Hua; Zhao, Jian-heng

    2015-01-01

    The refractive indices, absorption coefficients and complex dielectric constants spectra of paraffin-embedded brain glioma and normal brain tissues have been measured by a terahertz time domain spectroscopy (THz-TDS) system in the range of 0.2 - 2.0 THz. The spectral differences between glioma and normal brain tissues were obtained. Our results indicate that, compared with normal tissue, glioma had higher refractive index, absorption coefficient, and dielectric constant. Based on these results, the suitable frequency components for different methods of glioma imaging (intensity imaging, coherent imaging and terahertz pulsed imaging) are analyzed.

  17. Discrimination of genetically modified sugar beets based on terahertz spectroscopy.

    PubMed

    Chen, Tao; Li, Zhi; Yin, Xianhua; Hu, Fangrong; Hu, Cong

    2016-01-15

    The objective of this paper was to apply terahertz (THz) spectroscopy combined with chemometrics techniques for discrimination of genetically modified (GM) and non-GM sugar beets. In this paper, the THz spectra of 84 sugar beet samples (36 GM sugar beets and 48 non-GM ones) were obtained by using terahertz time-domain spectroscopy (THz-TDS) system in the frequency range from 0.2 to 1.2 THz. Three chemometrics methods, principal component analysis (PCA), discriminant analysis (DA) and discriminant partial least squares (DPLS), were employed to classify sugar beet samples into two groups: genetically modified organisms (GMOs) and non-GMOs. The DPLS method yielded the best classification result, and the percentages of successful classification for GM and non-GM sugar beets were both 100%. Results of the present study demonstrate the usefulness of THz spectroscopy together with chemometrics methods as a powerful tool to distinguish GM and non-GM sugar beets. PMID:26436847

  18. Discrimination of genetically modified sugar beets based on terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Li, Zhi; Yin, Xianhua; Hu, Fangrong; Hu, Cong

    2016-01-01

    The objective of this paper was to apply terahertz (THz) spectroscopy combined with chemometrics techniques for discrimination of genetically modified (GM) and non-GM sugar beets. In this paper, the THz spectra of 84 sugar beet samples (36 GM sugar beets and 48 non-GM ones) were obtained by using terahertz time-domain spectroscopy (THz-TDS) system in the frequency range from 0.2 to 1.2 THz. Three chemometrics methods, principal component analysis (PCA), discriminant analysis (DA) and discriminant partial least squares (DPLS), were employed to classify sugar beet samples into two groups: genetically modified organisms (GMOs) and non-GMOs. The DPLS method yielded the best classification result, and the percentages of successful classification for GM and non-GM sugar beets were both 100%. Results of the present study demonstrate the usefulness of THz spectroscopy together with chemometrics methods as a powerful tool to distinguish GM and non-GM sugar beets.

  19. Discrimination of genetically modified sugar beets based on terahertz spectroscopy.

    PubMed

    Chen, Tao; Li, Zhi; Yin, Xianhua; Hu, Fangrong; Hu, Cong

    2016-01-15

    The objective of this paper was to apply terahertz (THz) spectroscopy combined with chemometrics techniques for discrimination of genetically modified (GM) and non-GM sugar beets. In this paper, the THz spectra of 84 sugar beet samples (36 GM sugar beets and 48 non-GM ones) were obtained by using terahertz time-domain spectroscopy (THz-TDS) system in the frequency range from 0.2 to 1.2 THz. Three chemometrics methods, principal component analysis (PCA), discriminant analysis (DA) and discriminant partial least squares (DPLS), were employed to classify sugar beet samples into two groups: genetically modified organisms (GMOs) and non-GMOs. The DPLS method yielded the best classification result, and the percentages of successful classification for GM and non-GM sugar beets were both 100%. Results of the present study demonstrate the usefulness of THz spectroscopy together with chemometrics methods as a powerful tool to distinguish GM and non-GM sugar beets.

  20. Terahertz transmission vs reflection imaging and model-based characterization for excised breast carcinomas

    PubMed Central

    Bowman, Tyler; El-Shenawee, Magda; Campbell, Lucas K.

    2016-01-01

    This work presents experimental and analytical comparison of terahertz transmission and reflection imaging modes for assessing breast carcinoma in excised paraffin-embedded human breast tissue. Modeling for both transmission and reflection imaging is developed. The refractive index and absorption coefficient of the tissue samples are obtained. The reflection measurements taken at the system’s fixed oblique angle of 30° are shown to be a hybridization of TE and TM modes. The models are validated with transmission spectroscopy at fixed points on fresh bovine muscle and fat tissues. Images based on the calculated absorption coefficient and index of refraction of bovine tissue are successfully compared with the terahertz magnitude and phase measured in the reflection mode. The validated techniques are extended to 20 and 30 μm slices of fixed human lobular carcinoma and infiltrating ductal carcinoma mounted on polystyrene microscope slides in order to investigate the terahertz differentiation of the carcinoma with non-cancerous tissue. Both transmission and reflection imaging show clear differentiation in carcinoma versus healthy tissue. However, when using the reflection mode, in the calculation of the thin tissue properties, the absorption is shown to be sensitive to small phase variations that arise due to deviations in slide and tissue thickness and non-ideal tissue adhesion. On the other hand, the results show that the transmission mode is much less sensitive to these phase variations. The results also demonstrate that reflection imaging provides higher resolution and more clear margins between cancerous and fibroglandular regions, cancerous and fatty regions, and fibroglandular and fatty tissue regions. In addition, more features consistent with high power pathology images are exhibited in the reflection mode images.

  1. Terahertz transmission vs reflection imaging and model-based characterization for excised breast carcinomas

    PubMed Central

    Bowman, Tyler; El-Shenawee, Magda; Campbell, Lucas K.

    2016-01-01

    This work presents experimental and analytical comparison of terahertz transmission and reflection imaging modes for assessing breast carcinoma in excised paraffin-embedded human breast tissue. Modeling for both transmission and reflection imaging is developed. The refractive index and absorption coefficient of the tissue samples are obtained. The reflection measurements taken at the system’s fixed oblique angle of 30° are shown to be a hybridization of TE and TM modes. The models are validated with transmission spectroscopy at fixed points on fresh bovine muscle and fat tissues. Images based on the calculated absorption coefficient and index of refraction of bovine tissue are successfully compared with the terahertz magnitude and phase measured in the reflection mode. The validated techniques are extended to 20 and 30 μm slices of fixed human lobular carcinoma and infiltrating ductal carcinoma mounted on polystyrene microscope slides in order to investigate the terahertz differentiation of the carcinoma with non-cancerous tissue. Both transmission and reflection imaging show clear differentiation in carcinoma versus healthy tissue. However, when using the reflection mode, in the calculation of the thin tissue properties, the absorption is shown to be sensitive to small phase variations that arise due to deviations in slide and tissue thickness and non-ideal tissue adhesion. On the other hand, the results show that the transmission mode is much less sensitive to these phase variations. The results also demonstrate that reflection imaging provides higher resolution and more clear margins between cancerous and fibroglandular regions, cancerous and fatty regions, and fibroglandular and fatty tissue regions. In addition, more features consistent with high power pathology images are exhibited in the reflection mode images. PMID:27699136

  2. Coherent phonon spectroscopy of non-fully symmetric modes using resonant terahertz excitation

    SciTech Connect

    Huber, T. Huber, L.; Johnson, S. L.; Ranke, M.; Ferrer, A.

    2015-08-31

    We use intense terahertz (THz) frequency electromagnetic pulses generated via optical rectification in an organic crystal to drive vibrational lattice modes in single crystal Tellurium. The coherent modes are detected by measuring the polarization changes of femtosecond laser pulses reflecting from the sample surface, resulting in a phase-resolved detection of the coherent lattice motion. We compare the data to a model of Lorentz oscillators driven by the near-single-cycle broadband THz pulse. The demonstrated technique of optically probed coherent phonon spectroscopy with THz frequency excitation could prove to be a viable alternative to other time-resolved spectroscopic methods like standard THz time domain spectroscopy.

  3. Terahertz spectroscopy properties of the selected engine oils

    NASA Astrophysics Data System (ADS)

    Zhu, Shouming; Zhao, Kun; Lu, Tian; Zhao, Songqing; Zhou, Qingli; Shi, Yulei; Zhao, Dongmei; Zhang, Cunlin

    2010-11-01

    Engine oil, most of which is extracted from petroleum, consist of complex mixtures of hydrocarbons of molecular weights in the range of 250-1000. Variable amounts of different additives are put into them to inhibit oxidation, improve the viscosity index, decrease the fluidity point and avoid foaming or settling of solid particles among others. Terahertz (THz) spectroscopy contains rich physical, chemical, and structural information of the materials. Most low-frequency vibrational and rotational spectra of many petrochemicals lie in this frequency range. In recent years, much attention has been paid to the THz spectroscopic studies of petroleum products. In this paper, the optical properties and spectroscopy of selected kinds of engine oil consisting of shell HELIX 10W-40, Mobilube GX 80W-90, GEELY ENGINE OIL SG 10W-30, SMA engine oil SG 5W-30, SMA engine oil SG 10W-30, SMA engine oil SG 75W-90 have been studied by the terahertz time-domain spectroscopy (THz-TDS) in the spectral range of 0.6-2.5 THz. Engine oil with different viscosities in the terahertz spectrum has certain regularity. In the THz-TDS, with the increase of viscosity, time delay is greater and with the increase of viscosity, refractive indexes also grow and their rank is extremely regular. The specific kinds of engine oil can be identified according to their different spectral features in the THz range. The THz-TDS technology has potentially significant impact on the engine oil analysis.

  4. Nondestructive Evaluation of Carbon Fiber Reinforced Polymer Composites Using Reflective Terahertz Imaging.

    PubMed

    Zhang, Jin; Li, Wei; Cui, Hong-Liang; Shi, Changcheng; Han, Xiaohui; Ma, Yuting; Chen, Jiandong; Chang, Tianying; Wei, Dongshan; Zhang, Yumin; Zhou, Yufeng

    2016-06-14

    Terahertz (THz) time-domain spectroscopy (TDS) imaging is considered a nondestructive evaluation method for composite materials used for examining various defects of carbon fiber reinforced polymer (CFRP) composites and fire-retardant coatings in the reflective imaging modality. We demonstrate that hidden defects simulated by Teflon artificial inserts are imaged clearly in the perpendicular polarization mode. The THz TDS technique is also used to measure the thickness of thin fire-retardant coatings on CFRP composites with a typical accuracy of about 10 micrometers. In addition, coating debonding is successfully imaged based on the time-delay difference of the time-domain waveforms between closely adhered and debonded sample locations.

  5. Assessing skin hydration status in haemodialysis patients using terahertz spectroscopy: a pilot/feasibility study

    NASA Astrophysics Data System (ADS)

    Kadlec, Filip; Berta, Milan; Kužel, Petr; Lopot, František; Polakovič, Vladimír

    2008-12-01

    Terahertz (THz) time-domain spectroscopy was used in vivo to measure the body reflectance with the aim of determining experimentally the influence of haemodialysis on the content of water in the human skin. For this purpose, an original methodology of determining the skin properties at THz frequencies from the reflectance was developed. A series of measurements were performed before and after dialysis with ten subjects. The results strongly indicate that the surface body hydration is not the main parameter determining the skin conductivity in the THz range.

  6. Development of the technique of terahertz pulse spectroscopy for diagnostic malignant tumors during gastrointestinal surgeries

    NASA Astrophysics Data System (ADS)

    Goryachuk, A. A.; Khodzitsky, M. K.; Borovkova, M. A.; Khamid, A. K.; Dutkinskii, P. S.; Shishlo, D. A.

    2016-08-01

    Samples of fresh excised tissues obtained from patients who had undergone gastric cancer have been investigated. Samples were consisted of cancer zone, normal zone and zone mixed of normal and cancer tissues. Their optical properties and spectral features were investigated by terahertz time-domain spectroscopy (TDS) in reflection mode. It was found that waveforms of reflected signals from normal and cancer tissues were well distinguished so it can be concluded that it is easy to discriminate gastric cancer tissue from normal by using THz TDS.

  7. High power time domain terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Graber, Benjamin

    Terahertz (THz) has become a strong area for scientific research and commercial application in recent years. This research group has redesigned and optimized a THz photoconductive antenna, which currently operates with approximately 10x the power of a commercial antenna. It has been determined by this research that the THz signal emitted from a photoconductive antenna consists of coherent and incoherent signals. In addition to the improvement of the THz photoconductive antenna, I have optimized an electro optic THz detection system by characterizing the field dependency of an electro optic crystal, which enabled me to estimate the THz electric field strength. The high power THz source and optimized detection system were combined into a high power, high resolution time domain THz spectrometer. This spectrometer was used to conduct original measurements of the THz spectrum of water vapor, ionized air, and various chemical vapor including explosives. Most of these measurements were only possible with our improved THz spectrometer. In order to understand ionized air, an additional study was carried out to explore the ionization of several gases (e.g. N2, O2, Ar, CO2, and water vapor) which were ionized by radioactive isotopes. This unique study found that in addition to dose rate, the gamma energy of the radioactive isotopes and the sequential ionization levels of gases affect the equilibrium ion densities of these gases. This effect was especially pronounced for argon gas. The study of ion dynamics in gases has lead to the development of a prototype for stand-off detection and identification of radioactive isotopes. This prototype, despite being simple in design, can detect isotopes faster and more cheaply than a conventional gamma ray spectrometer. Throughout this thesis research I have successfully developed a high power, high resolution terahertz spectrometer and demonstrated that with the spectrometer I could identify characteristic resonances of water vapor, some

  8. Terahertz imaging and spectroscopy for landmine detection

    NASA Astrophysics Data System (ADS)

    Fitch, Michael J.; Schauki, Dunja; Kelly, Craig A.; Osiander, Robert

    2004-04-01

    Pulsed THz (100 GHz - 30 THz) Imaging Spectroscopy combines three ways of mine detection in one system, high resolution radar, depth ranging, and infrared spectroscopy. It allows minefield detection, single mine imaging, and near-zero false alarm due to the capabilities of explosives / plastic identification using spectroscopy with working distances to 1000 feet. We have previously demonstrated imaging capabilities with 1 mm spatial resolution on a rubber O-ring embedded in sand. The estimated transmission depth in moist sand is 1 to 3 cm, which should be sufficient for imaging anti-personnel mines. In this work, we present initial results investigating the feasibility of THz spectroscopy in the frequency range from 1 to 10 THz to detect and identify explosives and related compounds (ERCs). A major component of this effort is chemical modeling to obtain spectroscopic information on ERCs and environmental background. A time-domain THz system using femtosecond laser pulses is also being developed.

  9. Diffraction-limited ultrabroadband terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Baillergeau, M.; Maussang, K.; Nirrengarten, T.; Palomo, J.; Li, L. H.; Linfield, E. H.; Davies, A. G.; Dhillon, S.; Tignon, J.; Mangeney, J.

    2016-05-01

    Diffraction is the ultimate limit at which details of objects can be resolved in conventional optical spectroscopy and imaging systems. In the THz spectral range, spectroscopy systems increasingly rely on ultra-broadband radiation (extending over more 5 octaves) making a great challenge to reach resolution limited by diffraction. Here, we propose an original easy-to-implement wavefront manipulation concept to achieve ultrabroadband THz spectroscopy system with diffraction-limited resolution. Applying this concept to a large-area photoconductive emitter, we demonstrate diffraction-limited ultra-broadband spectroscopy system up to 14.5 THz with a dynamic range of 103. The strong focusing of ultrabroadband THz radiation provided by our approach is essential for investigating single micrometer-scale objects such as graphene flakes or living cells, and besides for achieving intense ultra-broadband THz electric fields.

  10. Diffraction-limited ultrabroadband terahertz spectroscopy

    PubMed Central

    Baillergeau, M.; Maussang, K.; Nirrengarten, T.; Palomo, J.; Li, L. H.; Linfield, E. H.; Davies, A. G.; Dhillon, S.; Tignon, J.; Mangeney, J.

    2016-01-01

    Diffraction is the ultimate limit at which details of objects can be resolved in conventional optical spectroscopy and imaging systems. In the THz spectral range, spectroscopy systems increasingly rely on ultra-broadband radiation (extending over more 5 octaves) making a great challenge to reach resolution limited by diffraction. Here, we propose an original easy-to-implement wavefront manipulation concept to achieve ultrabroadband THz spectroscopy system with diffraction-limited resolution. Applying this concept to a large-area photoconductive emitter, we demonstrate diffraction-limited ultra-broadband spectroscopy system up to 14.5 THz with a dynamic range of 103. The strong focusing of ultrabroadband THz radiation provided by our approach is essential for investigating single micrometer-scale objects such as graphene flakes or living cells, and besides for achieving intense ultra-broadband THz electric fields. PMID:27142959

  11. Spectroscopy and terahertz imaging for sigillography applications

    NASA Astrophysics Data System (ADS)

    Mounaix, P.; Younus, A.; Delagnes, J. C.; Abraham, E.; Canioni, L.; Fabre, M.

    2011-02-01

    Sigillography is the science that studies the manifold aspects of the seals. A seal can be defined as an imprint obtained on a malleable medium by imprinting an incised matrix, which transfers on it the characteristic signs of a person or an institution. We use THz spectroscopy and imaging for non-destructive evaluation of natural seals. Using a time domain THz spectroscopy and imaging system, THz transmission images are generated in the 0.1-3 THz range.

  12. Research of pesticide residues on fruit by terahertz spectroscopy technology

    NASA Astrophysics Data System (ADS)

    Ma, Yehao; Wang, Qiang; Wang, Xiaowei; Wang, Huali

    2011-11-01

    Pesticide residues on the fruit skin are measured by terahertz time-domain spectroscopy (THz-TDS) in 0.2-1.3THz. Pesticide is mainly residues for fruit, which threatens health of human, so the research about the fruit residues is absolutely important. In the experiment, a kind of pesticide carbendazim, orange, and the mixture of them are measured by THz-TDS, and then calculate absorption spectrums through Fourier transform and Fresnel formula. Experiment results indicate that THz-TDS is an effective tool for the measurement of pesticide residues on the fruit skin.

  13. Terahertz time-domain spectroscopy of four hydroxycinnamic acid derivatives.

    PubMed

    Ge, Min; Zhao, Hongwei; Wang, Wenfeng; Zhang, Zengyan; Yu, Xiaohan; Li, Wenxin

    2006-11-01

    The well-resolved absorption spectra of the hydroxycinnamic acid (HCA) derivatives, caffeic acid, ferulic acid, sinapic acid and chlorogenic acid, were measured over the frequency region from 0.3 to 2.0 THz at 294 K with terahertz time-domain spectroscopy (THz-TDS). Theoretical calculation was applied to assist the analysis and assignment of the individual THz absorption spectra of the HCA derivatives with density functional theory (DFT). The distinctive spectral features were originated from the collective motion of molecules held together by hydrogen bonds. The real and imaginary parts of dielectric function of the four HCA derivatives were also obtained. PMID:19669446

  14. Terahertz electromodulation spectroscopy of electron transport in GaN

    SciTech Connect

    Engelbrecht, S. G.; Arend, T. R.; Kersting, R.; Zhu, T.; Kappers, M. J.

    2015-03-02

    Time-resolved terahertz (THz) electromodulation spectroscopy is applied to investigate the high-frequency transport of electrons in gallium nitride at different doping concentrations and densities of threading dislocations. At THz frequencies, all structures reveal Drude transport. The analysis of the spectral response provides the fundamental transport properties, such as the electron scattering time and the electrons' conductivity effective mass. We observe the expected impact of ionized-impurity scattering and that scattering at threading dislocations only marginally affects the high-frequency mobility.

  15. Terahertz Time-Domain Spectroscopy of Four Hydroxycinnamic Acid Derivatives

    PubMed Central

    Ge, Min; Zhao, Hongwei; Zhang, Zengyan; Yu, Xiaohan; Li, Wenxin

    2006-01-01

    The well-resolved absorption spectra of the hydroxycinnamic acid (HCA) derivatives, caffeic acid, ferulic acid, sinapic acid and chlorogenic acid, were measured over the frequency region from 0.3 to 2.0 THz at 294 K with terahertz time-domain spectroscopy (THz-TDS). Theoretical calculation was applied to assist the analysis and assignment of the individual THz absorption spectra of the HCA derivatives with density functional theory (DFT). The distinctive spectral features were originated from the collective motion of molecules held together by hydrogen bonds. The real and imaginary parts of dielectric function of the four HCA derivatives were also obtained. PMID:19669446

  16. Terahertz pulse imaging in reflection geometry of human skin cancer and skin tissue

    NASA Astrophysics Data System (ADS)

    Woodward, Ruth M.; Cole, Bryan E.; Wallace, Vincent P.; Pye, Richard J.; Arnone, Donald D.; Linfield, Edmund H.; Pepper, Michael

    2002-11-01

    We demonstrate the application of terahertz pulse imaging (TPI) in reflection geometry for the study of skin tissue and related cancers both in vitro and in vivo. The sensitivity of terahertz radiation to polar molecules, such as water, makes TPI suitable for studying the hydration levels in the skin and the determination of the lateral spread of skin cancer pre-operatively. By studying the terahertz pulse shape in the time domain we have been able to differentiate between diseased and normal tissue for the study of basal cell carcinoma (BCC). Basal cell carcinoma has shown a positive terahertz contrast, and inflammation and scar tissue a negative terahertz contrast compared to normal tissue. In vivo measurements on the stratum corneum have enabled visualization of the stratum corneum-epidermis interface and the study of skin hydration levels. These results demonstrate the potential of terahertz pulse imaging for the study of skin tissue and its related disorders, both in vitro and in vivo.

  17. Characterization of Wheat Varieties Using Terahertz Time-Domain Spectroscopy

    PubMed Central

    Ge, Hongyi; Jiang, Yuying; Lian, Feiyu; Zhang, Yuan; Xia, Shanhong

    2015-01-01

    Terahertz (THz) spectroscopy and multivariate data analysis were explored to discriminate eight wheat varieties. The absorption spectra were measured using THz time-domain spectroscopy from 0.2 to 2.0 THz. Using partial least squares (PLS), a regression model for discriminating wheat varieties was developed. The coefficient of correlation in cross validation (R) and root-mean-square error of cross validation (RMSECV) were 0.985 and 1.162, respectively. In addition, interval PLS was applied to optimize the models by selecting the most appropriate regions in the spectra, improving the prediction accuracy (R = 0.992 and RMSECV = 0.967). Results demonstrate that THz spectroscopy combined with multivariate analysis can provide rapid, nondestructive discrimination of wheat varieties. PMID:26024421

  18. Taurid Compex reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Birlan, M.; Popescu, M.; Nedelcu, A.

    2014-07-01

    The Taurid complex is a massive stream of material in the inner part of the Solar System. Its name is related to the Taurid meteor shower. This complex is characterized by a cluster of objects having low-inclination (i < 12°), large-eccentricity (0.64--0.85) orbits with semimajor axes spanning the range 1.8--2.6 au. The largest body of the Taurid Complex is the comet P/Encke, and this complex contains more than 20 near-Earth asteroids (NEAs). There is an important lack of information concerning the physical parameters of the Taurid complex. The observational campaign for observing NEAs of the Taurid complex was started in 2011 in order to provide valuable spectroscopic data for characterizing the surfaces of the complex members. The paper presents near-infrared spectroscopy using IRTF/SpeX obtained remotely from Paris Observatory and Bucharest Observatory for the following asteroids: (2201) Oljato, (4183) Cuno, (4486) Mithra, (5243) Heracles, (6063) Jason, and (269690) 1996 RG_3. We will present a detailed analysis of these spectra which allows their association with several minerals and laboratory spectra of meteorites.

  19. Identification and classification of chemicals using terahertz reflective spectroscopic focal-plane imaging system

    NASA Astrophysics Data System (ADS)

    Zhong, Hua; Redo-Sanchez, Albert; Zhang, X.-C.

    2006-10-01

    We present terahertz (THz) reflective spectroscopic focal-plane imaging of four explosive and bio-chemical materials (2, 4-DNT, Theophylline, RDX and Glutamic Acid) at a standoff imaging distance of 0.4 m. The 2 dimension (2-D) nature of this technique enables a fast acquisition time and is very close to a camera-like operation, compared to the most commonly used point emission-detection and raster scanning configuration. The samples are identified by their absorption peaks extracted from the negative derivative of the reflection coefficient respect to the frequency (-dr/dv) of each pixel. Classification of the samples is achieved by using minimum distance classifier and neural network methods with a rate of accuracy above 80% and a false alarm rate below 8%. This result supports the future application of THz time-domain spectroscopy (TDS) in standoff distance sensing, imaging, and identification.

  20. 3D-Printed Broadband Dielectric Tube Terahertz Waveguide with Anti-Reflection Structure

    NASA Astrophysics Data System (ADS)

    Vogt, Dominik Walter; Leonhardt, Rainer

    2016-07-01

    We demonstrate broadband, low loss, and close-to-zero dispersion guidance of terahertz (THz) radiation in a dielectric tube with an anti-reflection structure (AR-tube waveguide) in the frequency range from 0.2 to 1.0 THz. The anti-reflection structure (ARS) consists of close-packed cones in a hexagonal lattice arranged on the outer surface of the tube cladding. The feature size of the ARS is in the order of the wavelength between 0.2 and 1.0 THz. The waveguides are fabricated with the versatile and cost efficient 3D-printing method. Terahertz time-domain spectroscopy (THz-TDS) measurements as well as 3D finite-difference time-domain simulations (FDTD) are performed to extensively characterize the AR-tube waveguides. Spectrograms, attenuation spectra, effective phase refractive indices, and the group-velocity dispersion parameters β 2 of the AR-tube waveguides are presented. Both the experimental and numerical results confirm the extended bandwidth and smaller group-velocity dispersion of the AR-tube waveguide compared to a low loss plain dielectric tube THz waveguide. The AR-tube waveguide prototypes show an attenuation spectrum close to the theoretical limit given by the infinite cladding tube waveguide.

  1. 3D-Printed Broadband Dielectric Tube Terahertz Waveguide with Anti-Reflection Structure

    NASA Astrophysics Data System (ADS)

    Vogt, Dominik Walter; Leonhardt, Rainer

    2016-11-01

    We demonstrate broadband, low loss, and close-to-zero dispersion guidance of terahertz (THz) radiation in a dielectric tube with an anti-reflection structure (AR-tube waveguide) in the frequency range from 0.2 to 1.0 THz. The anti-reflection structure (ARS) consists of close-packed cones in a hexagonal lattice arranged on the outer surface of the tube cladding. The feature size of the ARS is in the order of the wavelength between 0.2 and 1.0 THz. The waveguides are fabricated with the versatile and cost efficient 3D-printing method. Terahertz time-domain spectroscopy (THz-TDS) measurements as well as 3D finite-difference time-domain simulations (FDTD) are performed to extensively characterize the AR-tube waveguides. Spectrograms, attenuation spectra, effective phase refractive indices, and the group-velocity dispersion parameters β 2 of the AR-tube waveguides are presented. Both the experimental and numerical results confirm the extended bandwidth and smaller group-velocity dispersion of the AR-tube waveguide compared to a low loss plain dielectric tube THz waveguide. The AR-tube waveguide prototypes show an attenuation spectrum close to the theoretical limit given by the infinite cladding tube waveguide.

  2. Reflective terahertz (THz) imaging: system calibration using hydration phantoms

    NASA Astrophysics Data System (ADS)

    Bajwa, Neha; Garritano, James; Lee, Yoon Kyung; Tewari, Priyamvada; Sung, Shijun; Maccabi, Ashkan; Nowroozi, Bryan; Babakhanian, Meghedi; Sanghvi, Sajan; Singh, Rahul; Grundfest, Warren; Taylor, Zachary

    2013-02-01

    Terahertz (THz) hydration sensing continues to gain traction in the medical imaging community due to its unparalleled sensitivity to tissue water content. Rapid and accurate detection of fluid shifts following induction of thermal skin burns as well as remote corneal hydration sensing have been previously demonstrated in vivo using reflective, pulsed THz imaging. The hydration contrast sensing capabilities of this technology were recently confirmed in a parallel 7 Tesla Magnetic Resonance (MR) imaging study, in which burn areas are associated with increases in local mobile water content. Successful clinical translation of THz sensing, however, still requires quantitative assessments of system performance measurements, specifically hydration concentration sensitivity, with tissue substitutes. This research aims to calibrate the sensitivity of a novel, reflective THz system to tissue water content through the use of hydration phantoms for quantitative comparisons of THz hydration imagery.Gelatin phantoms were identified as an appropriate tissue-mimicking model for reflective THz applications, and gel composition, comprising mixtures of water and protein, was varied between 83% to 95% hydration, a physiologically relevant range. A comparison of four series of gelatin phantom studies demonstrated a positive linear relationship between THz reflectivity and water concentration, with statistically significant hydration sensitivities (p < .01) ranging between 0.0209 - 0.038% (reflectivity: %hydration). The THz-phantom interaction is simulated with a three-layer model using the Transfer Matrix Method with agreement in hydration trends. Having demonstrated the ability to accurately and noninvasively measure water content in tissue equivalent targets with high sensitivity, reflective THz imaging is explored as a potential tool for early detection and intervention of corneal pathologies.

  3. Non-invasive detection of murals with pulsed terahertz reflected imaging system

    NASA Astrophysics Data System (ADS)

    Yuan, Minjie; Sun, Wenfeng; Wang, Xinke; Ye, Jiasheng; Wang, Sen; Zhang, Qunxi; Zhang, Yan

    2015-11-01

    Pulsed terahertz reflected imaging technology has been expected to have great potential for the non-invasive analysis of artworks. In this paper, three types of defects hidden in the plaster used to simulate the cases of defects in the murals, have been investigated by a pulsed terahertz reflected imaging system. These preset defects include a circular groove, a cross-shaped slit and a piece of "Y-type" metal plate built in the plaster. With the terahertz reflective tomography, information about defects has been determined involving the thickness from the surface of sample to the built-in defect, the profile and distribution of the defect. Additionally, three-dimensional analyses have been performed in order to reveal the internal structure of defects. Terahertz reflective imaging can be applied to the defect investigation of the murals.

  4. Reflectance spectroscopy for soil analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Over the last three decades or more, researchers have estimated soil properties using visible and near infrared (VNIR) diffuse reflectance spectroscopy (DRS), with varying results. This presentation reviews the history and state-of –the art of VNIR-DRS, including relative estimation accuracy for var...

  5. Characteristics of Gadolinium Oxide Nanoparticles Using Terahertz Spectroscopy (abstract)

    NASA Astrophysics Data System (ADS)

    Lee, Dongkyu; Maeng, Inhee; Oh, Seung Jae; Kim, Taekhoon; Cho, Byung Kyu; Lee, Kwangyeol; Son, Joo-Hiuk

    2009-04-01

    The penetration property of the terahertz electromagnetic (THz) wave is relevant to its use. We used the THz wave spectroscopy system which easily penetrates some materials that do not contain water, e.g., plastic and ceramics. The system has been developed for several purposes, including measuring the properties of semiconductors and bio-materials, and detecting plastic bombs and ceramic knives at airports. It is also used for medical imaging systems, such as magnetic resonance imaging (MRI), at some research institutes. It can show not only the difference in amplitude, but also the difference of the phase of each point of sample. MRI technology usually uses contrast agents to enhance the quality of the image. Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA), made with a heavy metal ion, is commonly used as a clinical MRI contrast agent. Gadolinium oxide (Gd2O3) nanoparticle is a new contrast agent. It serves to equip the core of each particle with antibodies or ligands. It can freely circulate in blood vessels without amassing in the liver or lungs. This study shows the characteristics of gadolinium oxide nanoparticles to further advance terahertz medical imaging.

  6. Characteristics of Gadolinium Oxide Nanoparticles Using Terahertz Spectroscopy

    SciTech Connect

    Lee, Dongkyu; Maeng, Inhee; Son, Joo-Hiuk; Oh, Seung Jae; Kim, Taekhoon; Cho, Byung Kyu; Lee, Kwangyeol

    2009-04-19

    The penetration property of the terahertz electromagnetic (THz) wave is relevant to its use. We used the THz wave spectroscopy system which easily penetrates some materials that do not contain water, e.g., plastic and ceramics. The system has been developed for several purposes, including measuring the properties of semiconductors and bio-materials, and detecting plastic bombs and ceramic knives at airports. It is also used for medical imaging systems, such as magnetic resonance imaging (MRI), at some research institutes. It can show not only the difference in amplitude, but also the difference of the phase of each point of sample. MRI technology usually uses contrast agents to enhance the quality of the image. Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA), made with a heavy metal ion, is commonly used as a clinical MRI contrast agent. Gadolinium oxide (Gd{sub 2}O{sub 3}) nanoparticle is a new contrast agent. It serves to equip the core of each particle with antibodies or ligands. It can freely circulate in blood vessels without amassing in the liver or lungs. This study shows the characteristics of gadolinium oxide nanoparticles to further advance terahertz medical imaging.

  7. Terahertz-bandwidth pulses for coherent time-domain spectroscopy

    SciTech Connect

    Whitaker, J.F.; Gao, F.; Liu, Y.

    1994-12-31

    Ultrashort pulses of electromagnetic radiation propagating through free space are used to perform coherent time-domain spectroscopy by probing the complex index of refraction of various materials, in particular thin films of high-critical-temperature superconductors and the microwave substrates the support them. The terahertz beam system utilizes Hertz ion-dipole-like antennas consisting of a dc-biased photoconductive gap in a coplanar stripline as a transmitter, and an identical receiver with a photoconductive gap biased by the THz radiation. The transmitter is driven to produce the short radiation bursts by a 100-fs optical pulse from a Ti:sapphire self-mode-locked laser, while the receiver is synchronously gated by laser pulses split from the original beam. By performing measurements in the time domain and transforming data to the frequency domain, both the real and imaginary parts of the index of refraction of dielectrics and the conductivity of superconductors are determined over the entire range from {approximately}200 GHz to several terahertz. This technique allows the direct broadband determination of these quantities in the millimeter-wave and submillimeter-wave regimes from the measurement of only a few time-domain waveforms and without the need for Kramers-Kroenig analysis or complicated processing.

  8. Spectroscopic study of terahertz reflection and transmission properties of carbon-fiber-reinforced plastic composites

    NASA Astrophysics Data System (ADS)

    Zhang, Jin; Shi, Changcheng; Ma, Yuting; Han, Xiaohui; Li, Wei; Chang, Tianying; Wei, Dongshan; Du, Chunlei; Cui, Hong-Liang

    2015-05-01

    Carbon-fiber-reinforced plastic (CFRP) composites are widely used in aerospace and concrete structure reinforcement due to their high strength and light weight. Terahertz (THz) time-domain spectroscopy is an attractive tool for defect inspection in CFRP composites. In order to improve THz nondestructive testing of CFRP composites, we have carried out systematic investigations of THz reflection and transmission properties of CFRP. Unidirectional CFRP composites with different thicknesses are measured with polarization directions 0 deg to 90 deg with respect to the fiber direction, in both reflection and transmission modes. As shown in the experiments, CFRP composites are electrically conducting and therefore exhibit a high THz reflectivity. In addition, CFRP composites have polarization-dependent reflectivity and transmissivity for THz radiation. The reflected THz power in the case of parallel polarization is nearly 1.8 times higher than for perpendicular polarization. At the same time, in the transmission of THz wave, a CFRP acts as a Fabry-Pérot cavity resulting from multiple internal reflections from the CFRP-air interfaces. Moreover, from the measured data, we extract the refractive index and absorption coefficient of CFRP composites in the THz frequency range.

  9. Enhancement of terahertz reflection tomographic imaging by interference cancellation between layers.

    PubMed

    Park, Hochong; Son, Joo-Hiuk; Ahn, Chang-Beom

    2016-04-01

    This paper proposes a method to enhance terahertz reflection tomographic imaging by interference cancellation between layers. When the gap between layers is small, the signal reflected on the upper layer interferes with that on the lower layer, which degrades the quality of the reconstructed tomographic image in the lower layer. The proposed method estimates the upper-layer reflection signal by system modeling, which is then eliminated from the acquired signal. In this way, it can provide the correct lower-layer reflection signal, thereby improving the quality of the lower-layer tomographic image. The performance of the proposed method was confirmed using computer simulation data and real terahertz reflection data.

  10. Adaptive optics instrumentation in submillimeter/terahertz spectroscopy with a flexible polyvinylidene fluoride cladding hollow waveguide

    NASA Astrophysics Data System (ADS)

    Hidaka, Takehiko; Ishikawa, Akihiro; Kojou, Jun-Ichiro; Ikari, Tomofumi; Ishikawa, Yoh-Ichi; Minamide, Hiroaki; Kudoh, Akito; Nishizawa, Jun-Ichi; Ito, Hiromasa

    2007-08-01

    A simple instrument has been developed to carry out temperature dependent submillimeter/terahertz-wave spectroscopy using a polyvinylidene fluoride flexible hollow waveguide and an eggplant-shape launching lens.

  11. Nondestructive Evaluation of Carbon Fiber Reinforced Polymer Composites Using Reflective Terahertz Imaging.

    PubMed

    Zhang, Jin; Li, Wei; Cui, Hong-Liang; Shi, Changcheng; Han, Xiaohui; Ma, Yuting; Chen, Jiandong; Chang, Tianying; Wei, Dongshan; Zhang, Yumin; Zhou, Yufeng

    2016-01-01

    Terahertz (THz) time-domain spectroscopy (TDS) imaging is considered a nondestructive evaluation method for composite materials used for examining various defects of carbon fiber reinforced polymer (CFRP) composites and fire-retardant coatings in the reflective imaging modality. We demonstrate that hidden defects simulated by Teflon artificial inserts are imaged clearly in the perpendicular polarization mode. The THz TDS technique is also used to measure the thickness of thin fire-retardant coatings on CFRP composites with a typical accuracy of about 10 micrometers. In addition, coating debonding is successfully imaged based on the time-delay difference of the time-domain waveforms between closely adhered and debonded sample locations. PMID:27314352

  12. Nondestructive Evaluation of Carbon Fiber Reinforced Polymer Composites Using Reflective Terahertz Imaging

    PubMed Central

    Zhang, Jin; Li, Wei; Cui, Hong-Liang; Shi, Changcheng; Han, Xiaohui; Ma, Yuting; Chen, Jiandong; Chang, Tianying; Wei, Dongshan; Zhang, Yumin; Zhou, Yufeng

    2016-01-01

    Terahertz (THz) time-domain spectroscopy (TDS) imaging is considered a nondestructive evaluation method for composite materials used for examining various defects of carbon fiber reinforced polymer (CFRP) composites and fire-retardant coatings in the reflective imaging modality. We demonstrate that hidden defects simulated by Teflon artificial inserts are imaged clearly in the perpendicular polarization mode. The THz TDS technique is also used to measure the thickness of thin fire-retardant coatings on CFRP composites with a typical accuracy of about 10 micrometers. In addition, coating debonding is successfully imaged based on the time-delay difference of the time-domain waveforms between closely adhered and debonded sample locations. PMID:27314352

  13. Terahertz spectroscopy of ground state HD18O

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Pearson, John C.; Drouin, Brian J.; Miller, Charles E.; Kobayashi, Kaori; Matsushima, Fusakazu

    2016-10-01

    Terahertz absorption spectroscopy was employed to measure the ground state pure rotational transitions of the water isotopologue HD18O . A total of 105 pure rotational transitions were observed in the 0.5-5.0 THz region with ∼ 100 kHz accuracy for the first time. The observed positions were fit to experimental accuracy using the Euler series expansion of the asymmetric-top Hamiltonian together with the literature Microwave, Far-IR and IR data in the ground state and ν2 . The new measurements and predictions reported here support the analysis of astronomical observations by high-resolution spectroscopic telescopes such as SOFIA and ALMA where laboratory rest frequencies with uncertainties of 1 MHz or less are required for proper analysis of velocity resolved astrophysical data.

  14. Predicting Crystallization of Amorphous Drugs with Terahertz Spectroscopy.

    PubMed

    Sibik, Juraj; Löbmann, Korbinian; Rades, Thomas; Zeitler, J Axel

    2015-08-01

    There is a controversy about the extent to which the primary and secondary dielectric relaxations influence the crystallization of amorphous organic compounds below the glass transition temperature. Recent studies also point to the importance of fast molecular dynamics on picosecond-to-nanosecond time scales with respect to the glass stability. In the present study we provide terahertz spectroscopy evidence on the crystallization of amorphous naproxen well below its glass transition temperature and confirm the direct role of Johari-Goldstein (JG) secondary relaxation as a facilitator of the crystallization. We determine the onset temperature Tβ above which the JG relaxation contributes to the fast molecular dynamics and analytically quantify the level of this contribution. We then show there is a strong correlation between the increase in the fast molecular dynamics and onset of crystallization in several chosen amorphous drugs. We believe that this technique has immediate applications to quantify the stability of amorphous drug materials.

  15. Terahertz spectroscopy for bacterial detection: opportunities and challenges.

    PubMed

    Yang, Xiang; Yang, Ke; Luo, Yang; Fu, Weiling

    2016-06-01

    The demand for advanced bacterial detection tools is continuously increasing, promoted by its significant benefits in various applications. For instance, in the medical field, these tools would facilitate decision making about more tailored therapies once the infection source has been identified. In the past few years, terahertz (THz = 10(12) Hz) spectroscopy has also shown potential as a novel bacterial detection modality due to its unique advantages. Impressive breakthroughs have been achieved in this field related to bacterial component characterization, spore identification, and cell detection. However, some intrinsic limitations and technical bottlenecks have led to some debates about the practicability of its clinical adoption. In this review, we summarize the progress achieved in this field and discuss some challenges and strategies for future implementation of practical applications. PMID:27131501

  16. Terahertz time-domain spectroscopy of cotton sheets

    NASA Astrophysics Data System (ADS)

    Zhu, Yanhan; Holtz, Mark; Bernussi, Ayrton

    2012-10-01

    The transmission of cotton is measured using time-domain spectroscopy in the terahertz (THz) frequency range, from 0.1 to 1.5 THz. An effective medium approximation is used to model the combined cotton and air comprising the samples, and the refractive index of cotton fibers determined. The imaginary part of the refractive index varies across this frequency range with corresponding attenuation coefficient increasing from ˜ 2 to ˜ 12 cm-1, while the real part remains constant at n ˜ 1.144. The effect of moisture content is systematically examined and absorption of the samples determined. Concealed material detection was tested by measuring the 1.44-THz absorption band of representative substance D-Glucose embedded in cotton sheets.

  17. Amplification and modelling of bioaffinity detection with terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Mickan, Samuel P.; Menikh, Abdellah; Munch, Jesper; Abbott, Derek; Zhang, Xi-Cheng

    2002-11-01

    A new bioaffinity sensor based on pulsed terahertz (THz) spectroscopy is able to sensitively detect the presence of ultra-thin bound biomolecular layers. The protein avidin and lipid biotin are noted for their very high binding affinity, and the ease for which they can be attached to residues with importance in many biosensing applications. We demonstrate the sensitivity of the pulsed THz spectrometer to thin avidin layers and to avidin amplified with micron-sized agarose beads. The experimental results can be simply modelled by considering transmission of the THz radiation at the thin film interfaces. We detect less than 10.3 ng/cm2 avidin, giving the THz system a detection capability of sub-thin solid films better than ellipsometry and reflectometry techniques.

  18. Characterization of Poly-Amorphous Indomethacin by Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Otsuka, Makoto; Nishizawa, Jun-ichi; Fukura, Naomi; Sasaki, Tetsuo

    2012-09-01

    Since the stability of amorphous solids of pharmaceuticals differs depending on the method of preparation, there are several solid-state chemical structures in amorphous solids, which like poly-amorphous solids might have different characteristics the same as in crystalline solids. However, it is not easy to identify the differences in solid-state characteristics between amorphous solids using conventional analytical methods, such as powder X-ray diffraction analysis, since all of the poly-amorphous solids had similar halo X-ray diffraction patterns. However, terahertz spectroscopy can distinguish the amorphous solids of indomethacin with different physicochemical properties, and is expected to provide a rapid and non-destructive qualitative analysis for the solid materials, it would be useful for the qualitative evaluation of amorphous solids in the pharmaceutical industry.

  19. Characterization of Poly-Amorphous Indomethacin by Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Otsuka, Makoto; Nishizawa, Jun-ichi; Fukura, Naomi; Sasaki, Tetsuo

    2012-05-01

    Since the stability of amorphous solids of pharmaceuticals differs depending on the method of preparation, there are several solid-state chemical structures in amorphous solids, which like poly-amorphous solids might have different characteristics the same as in crystalline solids. However, it is not easy to identify the differences in solid-state characteristics between amorphous solids using conventional analytical methods, such as powder X-ray diffraction analysis, since all of the poly-amorphous solids had similar halo X-ray diffraction patterns. However, terahertz spectroscopy can distinguish the amorphous solids of indomethacin with different physicochemical properties, and is expected to provide a rapid and non-destructive qualitative analysis for the solid materials, it would be useful for the qualitative evaluation of amorphous solids in the pharmaceutical industry.

  20. Terahertz pulsed spectroscopy of paraffin-embedded brain glioma

    NASA Astrophysics Data System (ADS)

    Meng, Kun; Chen, Tu-nan; Chen, Tao; Zhu, Li-guo; Liu, Qiao; Li, Zhao; Li, Fei; Zhong, Sen-cheng; Li, Ze-ren; Feng, Hua; Zhao, Jian-heng

    2014-07-01

    The refractive indices, absorption coefficients, and complex dielectric constants of paraffin-embedded brain glioma and normal brain tissues have been measured by a terahertz time-domain spectroscopy (THz-TDS) system in the 0.2- to 2.0-THz range. The spectral differences between gliomas and normal brain tissues were obtained. Compared with normal brain tissue, our results indicate that paraffin-embedded brain gliomas have a higher refractive index, absorption coefficient, and dielectric constant. Based on these results, the best THz frequencies for different methods of paraffin-embedded brain glioma imaging, such as intensity imaging, coherent imaging with continuum THz sources, and THz pulsed imaging with short-pulsed THz sources, are analyzed.

  1. Reflection type of terahertz imaging system using a high-T{sub c} superconducting oscillator

    SciTech Connect

    Kashiwagi, T.; Minami, H.; Kadowaki, K.; Nakade, K.; Saiwai, Y.; Kitamura, T.; Watanabe, C.; Ishida, K.; Sekimoto, S.; Asanuma, K.; Yasui, T.; Shibano, Y.; Marković, B.; Mirković, J.; Tsujimoto, M.; Yamamoto, T.

    2014-01-13

    A reflection type of imaging system is shown at sub-terahertz frequencies generated from high-T{sub c} superconducting intrinsic Josephson junction mesa structures fabricated by single crystalline Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+δ} to demonstrate how the sub-terahertz imaging technique using monochromatic radiation is powerful and unique for the variety of practical applications. Several examples are discussed in detail and are compared to other terahertz imaging systems.

  2. Terahertz spectroscopy of concrete for evaluating the critical hydration level

    NASA Astrophysics Data System (ADS)

    Dash, Jyotirmayee; Ray, Shaumik; Nallappan, Kathirvel; Sasmal, Saptarshi; Pesala, Bala

    2014-03-01

    Concrete, a mixture of cement, coarse aggregate, sand and filler material (if any), is widely used in the construction industry. Cement, mainly composed of Tricalcium Silicate (C3S) and Dicalcium Silicate (C2S) reacts readily with water, a process known as hydration. The hydration process forms a solid material known as hardened cement paste which is mainly composed of Calcium Silicate Hydrate (C-S-H), Calcium Hydroxide and Calcium Carbonate. To quantify the critical hydration level, an accurate and fast technique is highly desired. However, in conventional XRD technique, the peaks of the constituents of anhydrated and hydrated cement cannot be resolved properly, where as Mid-infrared (MIR) spectroscopy has low penetration depth and hence cannot be used to determine the hydration level of thicker concrete samples easily. Further, MIR spectroscopy cannot be used to effectively track the formation of Calcium Hydroxide, a key by-product during the hydration process. This paper describes a promising approach to quantify the hydration dynamics of cement using Terahertz (THz) spectroscopy. This technique has been employed to track the time dependent reaction mechanism of the key constituents of cement that react with water and form the products in the hydrated cement, viz., C-S-H, Calcium Hydroxide and Calcium Carbonate. This study helps in providing an improved understanding on the hydration kinetics of cement and also to optimise the physio-mechanical characteristics of concrete.

  3. Quantitative measurement of permeabilization of living cells by terahertz attenuated total reflection

    NASA Astrophysics Data System (ADS)

    Grognot, Marianne; Gallot, Guilhem

    2015-09-01

    Using Attenuated Total Reflection imaging technique in the terahertz domain, we demonstrate non-invasive, non-staining real time measurements of cytoplasm leakage during permeabilization of epithelial cells by saponin. The terahertz signal is mostly sensitive to the intracellular protein concentration in the cells, in a very good agreement with standard bicinchoninic acid protein measurements. It opens the way to in situ real time dynamics of protein content and permeabilization in live cells.

  4. Cartilage analysis by reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Laun, T.; Muenzer, M.; Wenzel, U.; Princz, S.; Hessling, M.

    2015-07-01

    A cartilage bioreactor with analytical functions for cartilage quality monitoring is being developed. For determining cartilage composition, reflection spectroscopy in the visible (VIS) and near infrared (NIR) spectral region is evaluated. Main goal is the determination of the most abundant cartilage compounds water, collagen I and collagen II. Therefore VIS and NIR reflection spectra of different cartilage samples of cow, pig and lamb are recorded. Due to missing analytical instrumentation for identifying the cartilage composition of these samples, typical literature concentration values are used for the development of chemometric models. In spite of these limitations the chemometric models provide good cross correlation results for the prediction of collagen I and II and water concentration based on the visible and the NIR reflection spectra.

  5. Application of wavelet transforms in terahertz spectroscopy of rough surface targets

    NASA Astrophysics Data System (ADS)

    Arbab, M. Hassan; Winebrenner, Dale P.; Thorsos, Eric I.; Chen, Antao

    2010-02-01

    Previously, it has been shown that scattering of terahertz waves by surface roughness of a target can alter the terahertz absorption spectrum and thus obscure the detection of some chemicals in both transmission and reflection geometries. In this paper it is demonstrated that by employing Maximal Overlap Discrete Wavelet Transform (MODWT) coefficients, wavelet-based methods can be used to retrieve spectroscopic information from a broadband terahertz signal reflected from a rough surface target. It is concluded that while the commonly used direct frequency domain deconvolution method fails to accurately characterize and detect the resonance in the dielectric constant of rough surface lactose pellets, wavelet techniques were able to successfully identify such features.

  6. Terahertz metrology on power, frequency, spectroscopy, and pulse parameters

    NASA Astrophysics Data System (ADS)

    Wu, Bin; Ying, Cheng Ping; Wang, Heng Fei; Zhang, Peng; Liu, Hong Yuan; Jiang, Bin

    2015-11-01

    Terahertz metrology is becoming more and more important along with the fast development of terahertz technology. This paper reviews the research works of the groups from the physikalisch-technische bundesanstalt (PTB), National institute of standards and technology (NIST), National physical laboratory (NPL), National institute of metrology (NIM) and some other research institutes. The contents mainly focus on the metrology of parameters of power, frequency, spectrum and pulse. At the end of the paper, the prospect of terahertz metrology is predicted.

  7. 3-D Terahertz Synthetic-Aperture Imaging and Spectroscopy

    NASA Astrophysics Data System (ADS)

    Henry, Samuel C.

    Terahertz (THz) wavelengths have attracted recent interest in multiple disciplines within engineering and science. Situated between the infrared and the microwave region of the electromagnetic spectrum, THz energy can propagate through non-polar materials such as clothing or packaging layers. Moreover, many chemical compounds, including explosives and many drugs, reveal strong absorption signatures in the THz range. For these reasons, THz wavelengths have great potential for non-destructive evaluation and explosive detection. Three-dimensional (3-D) reflection imaging with considerable depth resolution is also possible using pulsed THz systems. While THz imaging (especially 3-D) systems typically operate in transmission mode, reflection offers the most practical configuration for standoff detection, especially for objects with high water content (like human tissue) which are opaque at THz frequencies. In this research, reflection-based THz synthetic-aperture (SA) imaging is investigated as a potential imaging solution. THz SA imaging results presented in this dissertation are unique in that a 2-D planar synthetic array was used to generate a 3-D image without relying on a narrow time-window for depth isolation cite [Shen 2005]. Novel THz chemical detection techniques are developed and combined with broadband THz SA capabilities to provide concurrent 3-D spectral imaging. All algorithms are tested with various objects and pressed pellets using a pulsed THz time-domain system in the Northwest Electromagnetics and Acoustics Research Laboratory (NEAR-Lab).

  8. Discrimination of transgenic soybean seeds by terahertz spectroscopy

    PubMed Central

    Liu, Wei; Liu, Changhong; Chen, Feng; Yang, Jianbo; Zheng, Lei

    2016-01-01

    Discrimination of genetically modified organisms is increasingly demanded by legislation and consumers worldwide. The feasibility of a non-destructive discrimination of glyphosate-resistant and conventional soybean seeds and their hybrid descendants was examined by terahertz time-domain spectroscopy system combined with chemometrics. Principal component analysis (PCA), least squares-support vector machines (LS-SVM) and PCA-back propagation neural network (PCA-BPNN) models with the first and second derivative and standard normal variate (SNV) transformation pre-treatments were applied to classify soybean seeds based on genotype. Results demonstrated clear differences among glyphosate-resistant, hybrid descendants and conventional non-transformed soybean seeds could easily be visualized with an excellent classification (accuracy was 88.33% in validation set) using the LS-SVM and the spectra with SNV pre-treatment. The results indicated that THz spectroscopy techniques together with chemometrics would be a promising technique to distinguish transgenic soybean seeds from non-transformed seeds with high efficiency and without any major sample preparation. PMID:27782205

  9. Quantitative analyses of tartaric acid based on terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Cao, Binghua; Fan, Mengbao

    2010-10-01

    Terahertz wave is the electromagnetic spectrum situated between microwave and infrared wave. Quantitative analysis based on terahertz spectroscopy is very important for the application of terahertz techniques. But how to realize it is still under study. L-tartaric acid is widely used as acidulant in beverage, and other food, such as soft drinks, wine, candy, bread and some colloidal sweetmeats. In this paper, terahertz time-domain spectroscopy is applied to quantify the tartaric acid. Two methods are employed to process the terahertz spectra of different samples with different content of tartaric acid. The first one is linear regression combining correlation analysis. The second is partial least square (PLS), in which the absorption spectra in the 0.8-1.4THz region are used to quantify the tartaric acid. To compare the performance of these two principles, the relative error of the two methods is analyzed. For this experiment, the first method does better than the second one. But the first method is suitable for the quantitative analysis of materials which has obvious terahertz absorption peaks, while for material which has no obvious terahertz absorption peaks, the second one is more appropriate.

  10. Gelatin embedding: a novel way to preserve biological samples for terahertz imaging and spectroscopy

    NASA Astrophysics Data System (ADS)

    Fan, Shuting; Ung, Benjamin; Parrott, Edward P. J.; Pickwell-MacPherson, Emma

    2015-04-01

    Sample dehydration has traditionally been a challenging problem in ex vivo terahertz biomedical experiments as water content changes significantly affect the terahertz properties and can diminish important contrast features. In this paper, we propose a novel method to prevent sample dehydration using gelatin embedding. By looking at terahertz image data and calculating the optical properties of the gelatin-embedded sample, we find that our method successfully preserves the sample for at least 35 h, both for imaging and spectroscopy. Our novel preservation method demonstrates for the first time the capability to simultaneously maintain sample structural integrity and prevent dehydration at room temperature. This is particularly relevant for terahertz studies of freshly excised tissues but could be beneficial for other imaging and spectroscopy techniques.

  11. Broadband terahertz time-domain spectroscopy : crystalline and glassy drug materials

    NASA Astrophysics Data System (ADS)

    Kojima, Seiji; Shibata, Tomohiko; Igawa, Hikaru; Mori, Tatsuya

    2014-03-01

    Low-energy IR active modes of glassy and crystalline drug materials were studied by the broadband Terahertz Time Domain Spectroscopy (THz-TDS) in the frequency range from 0.5 to 6.5 THz using a Cherenkov type THz generator. In order to determine the real and imaginary parts of complex dielectric constant, all samples were measured by the transmission using a pure pellet without mixing polyethylene. For glassy indomethacine, the broadband THz spectrum of real part of dielectric constant shows step-wise decrease with the increase of frequency, while the imaginary part shows a broad peak at about 3 THz reflecting quenched glassy disordered structure. The observed spectra of crystalline racemic ketoprofen show the noncoincidence of peak frequencies between low-frequency Raman scattering and THz absorbance spectra. It can be attributed to the fact that the mutual exclusion principle between Raman and IR activities holds below 6 THz.

  12. Vibrational spectrum of γ-HNIW investigated using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Guo, Lantao; Hu, Ying; Zhang, Yan; Zhang, Cunlin; Chen, Yunqing; Zhang, X.-C.

    2006-04-01

    Experimental and theoretical investigations of the vibration spectrum of γ-Hexanitrohexaazaisowurtzitane in the region of 0.2-2.5 terahertz are presented for the first time. The refraction index, absorption coefficient, and complex dielectric function of this sample are measured by terahertz time-domain spectroscopy. The simulated spectrum using density functional theory (DFT) is in agreement with the experimental data. The observed spectra features are assigned based on DFT calculation.

  13. Vibrational spectrum of gamma-HNIW investigated using terahertz time-domain spectroscopy.

    PubMed

    Guo, Lantao; Hu, Ying; Zhang, Yan; Zhang, Cunlin; Chen, Yunqing; Zhang, X-C

    2006-04-17

    Experimental and theoretical investigations of the vibration spectrum of gamma-Hexanitrohexaazaisowurtzitane in the region of 0.2-2.5 terahertz are presented for the first time. The refraction index, absorption coefficient, and complex dielectric function of this sample are measured by terahertz time-domain spectroscopy. The simulated spectrum using density functional theory (DFT) is in agreement with the experimental data. The observed spectra features are assigned based on DFT calculation.

  14. Direct observation of low frequency confined acoustic phonons in silver nanoparticles: Terahertz time domain spectroscopy.

    PubMed

    Kumar, Sunil; Kamaraju, N; Karthikeyan, B; Tondusson, M; Freysz, E; Sood, A K

    2010-07-01

    Terahertz time domain spectroscopy has been used to study low frequency confined acoustic phonons of silver nanoparticles embedded in poly(vinyl alcohol) matrix in the spectral range of 0.1-2.5 THz. The real and imaginary parts of the dielectric function show two bands at 0.60 and 2.12 THz attributed to the spheroidal and toroidal modes of silver nanoparticles, thus demonstrating the usefulness of terahertz time domain spectroscopy as a complementary technique to Raman spectroscopy in characterizing the nanoparticles.

  15. Few-cycle terahertz generation and spectroscopy of nanostructures.

    PubMed

    Darmo, Juraj; Müller, Thomas; Parz, Wolfgang; Kröll, Josef; Strasser, Gottfried; Unterrainer, Karl

    2004-02-15

    We report on new schemes for terahertz (THz) generation. The THz efficiency of photoconducting antennas can be increased by using a cavity effect for the near-infrared pump beam. The cavity is formed by a molecular beam epitaxy grown semiconductor Bragg mirror below the photoconducting layer. The optical confinement is accompanied by an electrical confinement suppressing undesired leakage currents and providing a constant electric field in the active layers. The performance of this cavity-enhanced emitter is further improved by using a mobility optimized low-temperature GaAs layer. This emitter is successfully used in a femtosecond Ti:sapphire laser cavity for highly efficient intracavity THz generation, where the photoconductive layer serves also as a saturable absorber. The broadband THz pulses generated are used for time-resolved spectroscopy of nanostructures. We study the dynamics of intersubband transitions in semiconductor quantum wells. The relaxation of carriers excited by a near-infrared pump pulse is investigated by measuring the THz absorption between the different subbands with our THz pulses. For transition energies below the optical phonon energy we find relatively long relaxation times with a strong dependence on the excited carrier density.

  16. Determining Phthalic Acid Esters Using Terahertz Time Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, L.; Shen, L.; Yang, F.; Han, F.; Hu, P.; Song, M.

    2016-09-01

    In this report terahertz time domain spectroscopy (THz-TDS) is applied for determining phthalic acid esters (PAEs) in standard materials. We reported the THz transmission spectrum in the frequency range of 0.2 to 2.0 THz for three PAEs: di-n-butyl phthalate (DBP), di-isononyl phthalate (DINP), and di-2-ethylhexyl phthalate ester (DEHP). The study provided the refractive indices and absorption features of these materials. The absorption spectra of three PAEs were simulated by using Gaussian software with Density Functional Theory (DFT) methods. For pure standard PAEs, the values of the refractive indices changed between 1.50 and 1.60. At 1.0 THz, the refractive indices were 1.524, 1.535, and 1.563 for DINP, DEHP, and DBP, respectively. In this experiment different concentrations of DBP were investigated using THz-TDS. Changes were measured in the low THz frequency range for refractive indices and characteristic absorption. The results indicated that THz-TDS is promising as a new method in determining PAEs in many materials. The results of this study could be used to support the practical application of THz-TDS in quality detection and food monitoring. In particular, this new technique could be used in detecting hazardous materials and other substances present in wine or foods.

  17. Improved Sensitivity MEMS Cantilever Sensor for Terahertz Photoacoustic Spectroscopy

    PubMed Central

    Coutu, Ronald A.; Medvedev, Ivan R.; Petkie, Douglas T.

    2016-01-01

    In this paper, a microelectromechanical system (MEMS) cantilever sensor was designed, modeled and fabricated to measure the terahertz (THz) radiation induced photoacoustic (PA) response of gases under low vacuum conditions. This work vastly improves cantilever sensitivity over previous efforts, by reducing internal beam stresses, minimizing out of plane beam curvature and optimizing beam damping. In addition, fabrication yield was improved by approximately 50% by filleting the cantilever’s anchor and free end to help reduce high stress areas that occurred during device fabrication and processing. All of the cantilever sensors were fabricated using silicon-on-insulator (SOI) wafers and tested in a custom built, low-volume, vacuum chamber. The resulting cantilever sensors exhibited improved signal to noise ratios, sensitivities and normalized noise equivalent absorption (NNEA) coefficients of approximately 4.28 × 10−10 cm−1·WHz−1/2. This reported NNEA represents approximately a 70% improvement over previously fabricated and tested SOI cantilever sensors for THz PA spectroscopy. PMID:26907280

  18. Time-domain terahertz spectroscopy of artificial skin

    NASA Astrophysics Data System (ADS)

    Corridon, Peter M.; Ascázubi, Ricardo; Krest, Courtney; Wilke, Ingrid

    2006-02-01

    Time-domain Terahertz (THz) spectroscopy and imaging is currently evaluated as a novel tool for medical imaging and diagnostics. The application of THz-pulse imaging of human skin tissues and related cancers has been demonstrated recently in-vitro and in-vivo. With this in mind, we present a time-domain THz-transmission study of artificial skin. The skin samples consist of a monolayer of porous matrix of fibers of cross-linked bovine tendon collagen and a glycosaminoglycan (chondroitin-6-sulfate) that is manufactured with a controlled porosity and defined degradation rate. Another set of samples consists of the collagen monolayer covered with a silicone layer. We have measured the THz-transmission and determined the index of refraction and absorption of our samples between 0.1 and 3 THz for various states of hydration in distilled water and saline solutions. The transmission of the THz-radiation through the artificial skin samples is modeled by electromagnetic wave theory. Moreover, the THz-optical properties of the artificial skin layers are compared to the THz-optical properties of freshly excised human skin samples. Based on this comparison the potential use of artificial skin samples as photo-medical phantoms for human skin is discussed.

  19. Improved Sensitivity MEMS Cantilever Sensor for Terahertz Photoacoustic Spectroscopy.

    PubMed

    Coutu, Ronald A; Medvedev, Ivan R; Petkie, Douglas T

    2016-01-01

    In this paper, a microelectromechanical system (MEMS) cantilever sensor was designed, modeled and fabricated to measure the terahertz (THz) radiation induced photoacoustic (PA) response of gases under low vacuum conditions. This work vastly improves cantilever sensitivity over previous efforts, by reducing internal beam stresses, minimizing out of plane beam curvature and optimizing beam damping. In addition, fabrication yield was improved by approximately 50% by filleting the cantilever's anchor and free end to help reduce high stress areas that occurred during device fabrication and processing. All of the cantilever sensors were fabricated using silicon-on-insulator (SOI) wafers and tested in a custom built, low-volume, vacuum chamber. The resulting cantilever sensors exhibited improved signal to noise ratios, sensitivities and normalized noise equivalent absorption (NNEA) coefficients of approximately 4.28 × 10(-10) cm(-1)·WHz(-1/2). This reported NNEA represents approximately a 70% improvement over previously fabricated and tested SOI cantilever sensors for THz PA spectroscopy.

  20. Terahertz Spectroscopy and Global Analysis of H_3O^+

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Drouin, Brian J.; Pearson, John C.; Pickett, Herbert M.

    2009-06-01

    Eight ground state inversion transitions of H_3O^+ in the 0.9-1.6 THz region have been measured using the frequency multiplier submillimeter spectrometer (FMSS) at JPL. The accuracy of these measurements is estimated to be 300 kHz. The ions were generated in a DC discharge through a gas mixture of a few mTorr of H_2 and 30 mTorr of H_2O. A multistate analysis was carried out for H_3O^+, which includes the lines observed in this work, previous submillimeter and terahertz inversion transitions in the ground state, and previous infrared data on all the four vibrational fundamental bands. Accurate molecular parameters were obtained with taking into account the strong Coriolis interaction between the symmetric OH stretching mode ν_1 and the doubly degenerate asymmetric OH stretching mode ν_3. Frequency predictions, particularly for high-J transitions in the ground state and in the ν_1 and ν_3 fundamental bands, have been greatly improved by including in our analysis 200 more high-J transitions, which were excluded in previous analyses. The more precise measurements and new predictions reported here will support the analysis of astronomical observations by the future high resolution spectroscopy telescopes such as Herschel, SOFIA, and ALMA.

  1. Improved Sensitivity MEMS Cantilever Sensor for Terahertz Photoacoustic Spectroscopy.

    PubMed

    Coutu, Ronald A; Medvedev, Ivan R; Petkie, Douglas T

    2016-01-01

    In this paper, a microelectromechanical system (MEMS) cantilever sensor was designed, modeled and fabricated to measure the terahertz (THz) radiation induced photoacoustic (PA) response of gases under low vacuum conditions. This work vastly improves cantilever sensitivity over previous efforts, by reducing internal beam stresses, minimizing out of plane beam curvature and optimizing beam damping. In addition, fabrication yield was improved by approximately 50% by filleting the cantilever's anchor and free end to help reduce high stress areas that occurred during device fabrication and processing. All of the cantilever sensors were fabricated using silicon-on-insulator (SOI) wafers and tested in a custom built, low-volume, vacuum chamber. The resulting cantilever sensors exhibited improved signal to noise ratios, sensitivities and normalized noise equivalent absorption (NNEA) coefficients of approximately 4.28 × 10(-10) cm(-1)·WHz(-1/2). This reported NNEA represents approximately a 70% improvement over previously fabricated and tested SOI cantilever sensors for THz PA spectroscopy. PMID:26907280

  2. Few-cycle terahertz generation and spectroscopy of nanostructures.

    PubMed

    Darmo, Juraj; Müller, Thomas; Parz, Wolfgang; Kröll, Josef; Strasser, Gottfried; Unterrainer, Karl

    2004-02-15

    We report on new schemes for terahertz (THz) generation. The THz efficiency of photoconducting antennas can be increased by using a cavity effect for the near-infrared pump beam. The cavity is formed by a molecular beam epitaxy grown semiconductor Bragg mirror below the photoconducting layer. The optical confinement is accompanied by an electrical confinement suppressing undesired leakage currents and providing a constant electric field in the active layers. The performance of this cavity-enhanced emitter is further improved by using a mobility optimized low-temperature GaAs layer. This emitter is successfully used in a femtosecond Ti:sapphire laser cavity for highly efficient intracavity THz generation, where the photoconductive layer serves also as a saturable absorber. The broadband THz pulses generated are used for time-resolved spectroscopy of nanostructures. We study the dynamics of intersubband transitions in semiconductor quantum wells. The relaxation of carriers excited by a near-infrared pump pulse is investigated by measuring the THz absorption between the different subbands with our THz pulses. For transition energies below the optical phonon energy we find relatively long relaxation times with a strong dependence on the excited carrier density. PMID:15306518

  3. Continuous-wave terahertz reflection imaging of ex vivo nonmelanoma skin cancers

    NASA Astrophysics Data System (ADS)

    Joseph, Cecil S.; Yaroslavsky, Anna N.; Neel, Victor A.; Goyette, Thomas M.; Giles, Robert H.

    2012-02-01

    Nonmelanoma skin cancers are the most common form of cancer. Continuous wave terahertz imaging has the potential to differentiate between nonmelanoma skin cancers and normal skin. Terahertz imaging is non-ionizing and offers a high sensitivity to water content. Contrast between cancerous and normal tissue in transmission mode has already been demonstrated using a continuous wave terahertz system. The aim of this experiment was to implement a system that is capable of reflection modality imaging of nonmelanoma skin cancers. Fresh excisions of skin cancer specimens were obtained from Mohs surgeries for this study. A CO2 optically pumped far-infrared molecular gas laser was used for illuminating the tissue at 584 GHz. The reflected signal was detected using a liquid Helium cooled Silicon bolometer. The terahertz images were compared with sample histology. The terahertz reflection images exhibit some artifacts that can hamper the specificity. The beam waist at the sample plane was measured to be 0.57 mm, and the system's signal-to-noise ratio was measured to be 65 dB.

  4. Terahertz pulse imaging in reflection geometry of skin tissue using time-domain analysis techniques

    NASA Astrophysics Data System (ADS)

    Woodward, Ruth M.; Wallace, Vincent P.; Cole, Bryan E.; Pye, Richard J.; Arnone, Donald D.; Linfield, Edmund H.; Pepper, Michael

    2002-06-01

    We demonstrate the application of Terahertz Pulse Imaging (TPI) in reflection geometry for the study of skin tissue and related cancers. The terahertz frequency regime of 0.1-100THz excites the vibrational modes of molecules, allowing for spectroscopic investigation. The sensitivity of terahertz to polar molecules, such as water, makes TPI suitable for studying the hydration levels in the stratum corneum and the determination of the lateral spread of skin cancer pre-operatively. By studying the terahertz pulse shape in the time domain we have been able to differentiate between diseased and normal tissue for the study of basal cell carcinoma (BCC). Measurements on scar tissue, which is known to contain less water than the surrounding skin, and on regions of inflammation, show a clear contrast in the THz image compared to normal skin. We discuss the time domain analysis techniques used to classify the different tissue types. Basal cell carcinoma shows a positive terahertz contrast, and inflammation and scar tissue shows a negative terahertz contrast compared to normal tissue. This demonstrates for the first time the potential of TPI both in the study of skin cancer and inflammatory related disorders.

  5. Etude de la dynamique des porteurs dans des nanofils de silicium par spectroscopie terahertz

    NASA Astrophysics Data System (ADS)

    Beaudoin, Alexandre

    Ce memoire presente une etude des proprietes de conduction electrique et de la dynamique temporelle des porteurs de charges dans des nanofils de silicium sondes par rayonnement terahertz. Les cas de nanofils de silicium non intentionnellement dopes et dopes type n sont compares pour differentes configurations du montage experimental. Les mesures de spectroscopie terahertz en transmission montre qu'il est possible de detecter la presence de dopants dans les nanofils via leur absorption du rayonnement terahertz (˜ 1--12 meV). Les difficultes de modelisation de la transmission d'une impulsion electromagnetique dans un systeme de nanofils sont egalement discutees. La detection differentielle, une modification au systeme de spectroscopie terahertz, est testee et ses performances sont comparees au montage de caracterisation standard. Les instructions et des recommendations pour la mise en place de ce type de mesure sont incluses. Les resultats d'une experience de pompe optique-sonde terahertz sont egalement presentes. Dans cette experience, les porteurs de charge temporairement crees suite a l'absorption de la pompe optique (lambda ˜ 800 nm) dans les nanofils (les photoporteurs) s'ajoutent aux porteurs initialement presents et augmentent done l'absorption du rayonnement terahertz. Premierement, l'anisotropie de l'absorption terahertz et de la pompe optique par les nanofils est demontree. Deuxiemement, le temps de recombinaison des photoporteurs est etudie en fonction du nombre de photoporteurs injectes. Une hypothese expliquant les comportements observes pour les nanofils non-dopes et dopes-n est presentee. Troisiemement, la photoconductivite est extraite pour les nanofils non-dopes et dopes-n sur une plage de 0.5 a 2 THz. Un lissage sur la photoconductivite permet d'estimer le nombre de dopants dans les nanofils dopes-n. Mots-cles: nanofil, silicium, terahertz, conductivite, spectroscopie, photoconductivite.

  6. Terahertz and Infrared Laboratory Spectroscopy in Support of NASA Missions

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan

    2015-06-01

    The JPL molecular spectroscopy group supports NASA programs encompassing Astrophysics, Atmospheric Science, and Planetary Science. Ongoing activities include measurement and analysis of molecular spectra in the terahertz and infrared regions under conditions akin to the remote environments under study in NASA missions. This presentation will show the implementation of state-of-the-art spectroscopic techniques to fulfill spectroscopic demands of the Herschel Space Observatory and the Orbiting Carbon Observatory re-flight (OCO-2). A demonstrative example of the significantly improved frequency predictions for the H_3O^+ ground state high-J transitions will be given. This work was critical to Herschel's successful identification of highly excited metastable H_3O^+ Terahertz lines with J=K up to 11, one of the Herschel mission's many surprising observational results. The observation and subsequent laboratory work revealed that (1) these highly excited H_3O^+ lines had already been observed by European Southern Observatory's Atacama Pathfinder Experiment telescope a few years before but had been classified as U-lines; (2) the H_3O^+ number density was previously underestimated by an order of magnitude, due to ignorance of the population in the metastable states. A second example focuses on O_2, an important absorber from the microwave through the deep UV. This work is motivated by the challenge of developing an accurate and complete spectroscopic characterization of molecular oxygen across a wide frequency range for current and planned Earth atmospheric observations. Especially, OCO-2 utilizes the O_2 A-band for air mass calibration; extremely accurate O_2 molecular data, i.e., line positions with uncertainty on the order of MHz for the A-band around 13000 wn, are required to fulfill the demand of the proposed 0.25% precision for the carbon dioxide concentration retrievals. G. Pilbratt, J. Riedinger, T. Passvogel, G. Crone, D. Doyle, U. Gageur et al. A&A, 518, L1 (2010

  7. Laminated helmet materials characterization by terahertz kinetics spectroscopy

    NASA Astrophysics Data System (ADS)

    Rahman, Anis; Rahman, Aunik K.

    2015-05-01

    High speed acquisition of reflected terahertz energy constitutes a kinetics spectrum that is an effective tool for layered materials' deformation characterization under ballistic impact. Here we describe utilizing the kinetics spectrum for quantifying a deformation event due to impact in material used for Soldier's helmet. The same technique may be utilized for real-time assessment of trauma by measuring the helmet wore by athletes. The deformation of a laminated material (e.g., a helmet) is dependent on the nature of impact and projectile; thus can uniquely characterize the impact condition leading to a diagnostic procedure based on the energy received by an athlete during an impact. We outline the calibration process for a given material under ballistic impact and then utilize the calibration for extracting physical parameters from the measured kinetics spectrum. Measured kinetics spectra are used to outline the method and rationale for extending the concept to a diagnosis tool. In particular, captured kinetics spectra from multilayered plates subjected to ballistic hit under experimental conditions by high speed digital acquisition system. An algorithm was devised to extract deformation and deformation velocity from which the energy received on the skull was estimated via laws of nonrelativistic motion. This energy is assumed to be related to actual injury conditions, thus forming a basis for determining whether the hit would cause concussion, trauma, or stigma. Such quantification may be used for diagnosing a Soldier's trauma condition in the field or that of an athlete's.

  8. Terahertz time-domain spectroscopy for distinguishing different kinds of gunpowder

    NASA Astrophysics Data System (ADS)

    Gavenda, TomáÅ.¡; Křesálek, Vojtech

    2013-10-01

    This article contains information about using terahertz time-domain spectroscopy for the security industry, particularly for distinguishing chosen different kinds of gunpowder. The original focus of described research was the observation of characteristic spectrum of gunpowder (spectral fingerprint) in the terahertz range of the electromagnetic spectrum to use the terahertz radiation for gunpowder detection and identification. The results of this research lead to the finding that researched samples of gunpowder do not have any characteristic spectral lines or peaks in the terahertz range of the electromagnetic spectrum up to 2 THz. However, the comparison of samples of different kinds of gunpowder proves the possibility of their distinguishing by their absorbance (absorption spectrum). Introduction information about motivation of authors, methods of measurement, samples preparation, results of measurements with their interpretation and discussion about the results with conclusion are the main parts of this article.

  9. Terahertz-visible two-photon rotational spectroscopy of cold OD-

    NASA Astrophysics Data System (ADS)

    Lee, Seunghyun; Hauser, Daniel; Lakhmanskaya, Olga; Spieler, Steffen; Endres, Eric S.; Geistlinger, Katharina; Kumar, Sunil S.; Wester, Roland

    2016-03-01

    We present a method to measure rotational transitions of molecular anions in the terahertz domain by sequential two-photon absorption. Ion excitation by bound-bound terahertz absorption is probed by absorption in the visible on a bound-free transition. The visible frequency is tuned to a state-selective photodetachment transition of the excited anions. This provides a terahertz action spectrum for just a few hundred molecular ions. To demonstrate this we measure the two lowest rotational transitions, J =1 ←0 and J =2 ←1 of OD- anions in a cryogenic 22-pole trap. We obtain rotational transition frequencies of 598 596.08(19) MHz for J =1 ←0 and 1 196 791.57(27) MHz for J =2 ←1 of OD-, in good agreement with their only previous measurement. This two-photon scheme opens up terahertz rovibrational spectroscopy for a range of molecular anions, in particular for polyatomic and cluster anions.

  10. Origin and quantification of differences between normal and tumor tissues observed by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Sayuri; Fukushi, Yasuko; Kubota, Oichi; Itsuji, Takeaki; Ouchi, Toshihiko; Yamamoto, Seiji

    2016-09-01

    The origin of the differences in the refractive index observed between normal and tumor tissues using terahertz spectroscopy has been described quantitatively. To estimate water content differences in tissues, we prepared fresh and paraffin-embedded samples from rats. An approximately 5% increase of water content in tumor tissues was calculated from terahertz time domain spectroscopy measurements compared to normal tissues. A greater than 15% increase in percentage of cell nuclei per unit area in tumor tissues was observed by hematoxylin and eosin stained samples, which generates a higher refractive index of biological components other than water. Both high water content and high cell density resulted in higher refractive index by approximately 0.05 in tumor tissues. It is predicted that terahertz spectroscopy can also be used to detect brain tumors in human tissue due to the same underlying mechanism as in rats.

  11. Probing structure and phase-transitions in molecular crystals by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Franz, Morten; Fischer, Bernd M.; Walther, Markus

    2011-12-01

    Since the introduction of ultra-fast laser techniques for the generation and detection of broadband terahertz pulses, terahertz time-domain spectroscopy has become a versatile tool for vibrational spectroscopy of molecular systems in the far-infrared. Due to their highly collective and delocalized character vibrational modes in this part of the spectrum are highly sensitive to molecular structure and arrangement within a molecular crystal. Here we utilize this sensitivity to differentiate between the enantiopure amino acid L-cysteine and its racemic crystalline DL-form. Using terahertz time-domain spectroscopy we are able to observe temperature induced solid-state phase transitions in polycrystalline DL-cysteine, as well as in polycrystalline benzoic acid. The dynamics of the transitions is studied by tracing the temperature dependency of spectral features that are assigned to certain conformational phases.

  12. Terahertz spectroscopy and detection of brain tumor in rat fresh-tissue samples

    NASA Astrophysics Data System (ADS)

    Yamaguchi, S.; Fukushi, Y.; Kubota, O.; Itsuji, T.; Yamamoto, S.; Ouchi, T.

    2015-03-01

    Terahertz (THz) spectroscopy and imaging of biomedical samples is expected to be an important application of THz analysis techniques. Identification and localization of tumor tissue, imaging of biological samples, and analysis of DNA by THz spectroscopy have been reported. THz time-domain spectroscopy (TDS) is useful for obtaining the refractive index over a broad frequency range. However, THz-TDS spectra of fresh tissue samples are sensitive to procedures such as sample preparation, and a standardized measurement protocol is required. Therefore, in this work, we establish a protocol for measurements of THz spectra of fresh tissue and demonstrate reliable detection of rat brain tumor tissue. We use a reflection THz-TDS system to measure the refractive index spectra of the samples mounted on a quartz plate. The tissue samples were measured immediately after sectioning to avoid sample denaturalization during storage. Special care was taken in THz data processing to eliminate parasitic reflections and reduce noise. The error level in our refractive index measurements was as low as 0.02 in the frequency range 0.8-1.5 THz. With increasing frequency, the refractive index in the tumor and normal regions monotonically decreased, similarly to water, and it was 0.02 higher in the tumor regions. The spectral data suggest that the tumor regions have higher water content. Hematoxylin-eosin stained images showed that increased cell density was also responsible for the observed spectral features. A set of samples from 10 rats showed consistent results. Our results suggest that reliable tumor detection in fresh tissue without pretreatment is possible with THz spectroscopy measurements. THz spectroscopy has the potential to become a real-time in vivo diagnostic method.

  13. Terahertz deconvolution.

    PubMed

    Walker, Gillian C; Bowen, John W; Labaune, Julien; Jackson, J-Bianca; Hadjiloucas, Sillas; Roberts, John; Mourou, Gerard; Menu, Michel

    2012-12-01

    The ability to retrieve information from different layers within a stratified sample using terahertz pulsed reflection imaging and spectroscopy has traditionally been resolution limited by the pulse width available. In this paper, a deconvolution algorithm is presented which circumvents this resolution limit, enabling deep sub-wavelength and sub-pulse width depth resolution. The algorithm is explained through theoretical investigation, and demonstrated by reconstructing signals reflected from boundaries in stratified materials that cannot be resolved directly from the unprocessed time-domain reflection signal. Furthermore, the deconvolution technique has been used to recreate sub-surface images from a stratified sample: imaging the reverse side of a piece of paper. PMID:23262673

  14. Evaluation of hydration in a water-soluble polymer by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Kawabe, Shunsuke; Seki, Munetoshi; Tabata, Hitoshi

    2016-02-01

    In this study, we have evaluated the hydration properties of water-soluble polymers by terahertz spectroscopy. In particular, we focused on polyvinylpyrrolidone which has potential use for a wide range of applications as a biomaterial. The dielectric loss of samples obtained by the terahertz spectroscopy was found to strongly depend on the molecular weight of the polymers and the density of the solution. We revealed that the hydration number per monomer depends on the molecular weight of the polymer. It is also deduced that the hydration number is affected by the conformation of the polymer in the solution.

  15. Characterization of primary and permanent teeth using terahertz spectroscopy

    PubMed Central

    Yetimoĝlu, N Ö; Altan, H

    2014-01-01

    Objectives: To analyse teeth samples by using terahertz time-domain spectroscopy (THz-TDS) system that was developed in the laboratory to measure the properties of sliced teeth sections in transmission mode. Methods: Using home-built THz-TDS system, we analysed a total of 25 teeth samples (9 primary and 16 permanent teeth). For transmission measurements, the refractive index and absorptive properties of the teeth sections were calculated. Difference between groups was tested using Mann–Whitney U-test statistics at the specific frequency of 0.5 THz, which was at the midpoint of the bandwidth. Median and minimum–maximum values were given as descriptive statistics. Type-I error rate was taken as α = 0.05. Results: Median refractive index values for permanent and primary teeth were found to be 2.53 and 2.54, respectively. Median absorption coefficient values for permanent and primary teeth were found to be 26.29 and 29.67, respectively. Median refractive index values for both healthy and carious teeth were found to be 2.54. Median absorption coefficient values for healthy and carious teeth were found to be 26.52 and 27.13, respectively. Although higher median absorption coefficient values were found for primary and carious teeth than those of permanent and healthy teeth, the differences were insignificant (p > 0.05). In addition, no statistical differences were found for refractive index values among different groups (p > 0.05). Conclusions: THz imaging has the potential to be used in assessing dental structures. PMID:24940807

  16. Terahertz spectroscopy and imaging for cultural heritage management: state of art and perspectives

    NASA Astrophysics Data System (ADS)

    Catapano, Ilaria; Soldovieri, Francesco

    2014-05-01

    molecular stability of the exposed objects and humans. Recently, the interest on THz technology is also growing up thanks to the development of flexible and compact commercial systems having source and detector probes coupled by means of optical fiber cables and that do not require complex optical alignments. These features allow us to reconfigure the measurement configuration easily; thus transmission, normal reflection and oblique reflection data can be collected according to the constrains and objective of the survey to be performed. Moreover, they open the way to on field applications. An example of last generation THz systems is the Fiber-Coupled Terahertz Time Domain System (FICO) marketed by Z-Omega and available at the Institute of Electromagnetic Sensing of the Environment. Such a system is designed to perform both transmission and reflection spectroscopy and imaging measurements in the range from 60GHz to 3THz; with a waveform acquisition speed up to 500Hz. A review of the literature assessing potentialities and open challenges of THz spectroscopy and imaging in the frame of cultural heritage preservation will be provided at the conferences, with a specific focus on the diagnostic capabilities of last generation systems. REFERENCES [1] K. Fukunaga, I. Hosako, Innovative non-invasive analysis techniques for cultural heritage using terahertz technology, C. R. Physique, vol. 11, pp.519-526, 2010. [2] G.Fillippidis, M. Massaouti, A. Selimis, E.J. Gualda, J.M. Manceau, S. Tzortzakis, Nonlinear imaging and THz diagnostic tools in the service of Cultural Heritage, Appl. Phys. A, vol.106, pp.257-263, 2012.

  17. Analysis of 3D-printed metal for rapid-prototyped reflective terahertz optics.

    PubMed

    Headland, Daniel; Withayachumnankul, Withawat; Webb, Michael; Ebendorff-Heidepriem, Heike; Luiten, Andre; Abbott, Derek

    2016-07-25

    We explore the potential of 3D metal printing to realize complex conductive terahertz devices. Factors impacting performance such as printing resolution, surface roughness, oxidation, and material loss are investigated via analytical, numerical, and experimental approaches. The high degree of control offered by a 3D-printed topology is exploited to realize a zone plate operating at 530 GHz. Reflection efficiency at this frequency is found to be over 90%. The high-performance of this preliminary device suggest that 3D metal printing can play a strong role in guided-wave and general beam control devices in the terahertz range. PMID:27464185

  18. Analysis of 3D-printed metal for rapid-prototyped reflective terahertz optics

    NASA Astrophysics Data System (ADS)

    Headland, Daniel; Withayachumnankul, Withawat; Webb, Michael; Ebendorff-Heidepriem, Heike; Luiten, Andre; Abbott, Derek

    2016-07-01

    We explore the potential of 3D metal printing to realize complex conductive terahertz devices. Factors impacting performance such as printing resolution, surface roughness, oxidation, and material loss are investigated via analytical, numerical, and experimental approaches. The high degree of control offered by a 3D-printed topology is exploited to realize a zone plate operating at 530 GHz. Reflection efficiency at this frequency is found to be over 90%. The high-performance of this preliminary device suggest that 3D metal printing can play a strong role in guided-wave and general beam control devices in the terahertz range.

  19. Generation of terahertz radiation in the reflection of a laser pulse from a dense plasma

    SciTech Connect

    Frolov, A. A.

    2007-12-15

    The generation of low-frequency (terahertz) electromagnetic radiation in the reflection of a laser pulse from the boundary of a dense plasma is considered. Low-frequency wave electromagnetic fields in vacuum are excited by a vortex electric current that is induced at the plasma boundary by the ponderomotive force of the laser pulse. The spectral, angular, and energy parameters of the low-frequency radiation, as well as the spatiotemporal structure of the emitted waves, are investigated. It is shown that for typical parameters of present-day laser plasma experiments, the power of terahertz radiation can amount to tens of megawatts.

  20. Analysis of 3D-printed metal for rapid-prototyped reflective terahertz optics.

    PubMed

    Headland, Daniel; Withayachumnankul, Withawat; Webb, Michael; Ebendorff-Heidepriem, Heike; Luiten, Andre; Abbott, Derek

    2016-07-25

    We explore the potential of 3D metal printing to realize complex conductive terahertz devices. Factors impacting performance such as printing resolution, surface roughness, oxidation, and material loss are investigated via analytical, numerical, and experimental approaches. The high degree of control offered by a 3D-printed topology is exploited to realize a zone plate operating at 530 GHz. Reflection efficiency at this frequency is found to be over 90%. The high-performance of this preliminary device suggest that 3D metal printing can play a strong role in guided-wave and general beam control devices in the terahertz range.

  1. Highly sensitive terahertz spectroscopy of residual pesticide using nano-antenna

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Kyu; Kim, Giyoung; Son, Joo-Hiuk; Seo, Minah

    2016-02-01

    In this report, a novel type of highly sensitive small molecule sensing tool has been employed to detect residual pesticide molecules including e. g. methomyl using terahertz (THz) time-domain spectroscopy (TDS) system with nano-slotantenna array. Enhance THz wave by the nano-slot-antenna array induces strong THz field enhancement around nano antenna and thus increases an absorption cross section leading to the detection sensitivity upto ppm level even in solution state. Measured spectrums in transmission and reflection show an excellent performance in both sensitivity and selectivity. We also tested the performance of our nano-antenna array in reflection imaging geometry to simply detect the contained residual pesticide at the real fruit surface as it is, without any extraction or sampling preprocess. The clear difference in the obtained THz reflection image distinguishes the stained area with methomyl from the bare area. Our observation can offer the possibility for further application as a prompt and an accurate small molecule monitoring tool in real time. A quantitative analysis tool for such small molecule can be also developed by this method.

  2. Indirect Terahertz Spectroscopy of Molecular Ions Using Highly Accurate and Precise Mid-Ir Spectroscopy

    NASA Astrophysics Data System (ADS)

    Mills, Andrew A.; Ford, Kyle B.; Kreckel, Holger; Perera, Manori; Crabtree, Kyle N.; McCall, Benjamin J.

    2009-06-01

    With the advent of Herschel and SOFIA, laboratory methods capable of providing molecular rest frequencies in the terahertz and sub-millimeter regime are increasingly important. As of yet, it has been difficult to perform spectroscopy in this wavelength region due to the limited availability of radiation sources, optics, and detectors. Our goal is to provide accurate THz rest frequencies for molecular ions by combining previously recorded microwave transitions with combination differences obtained from high precision mid-IR spectroscopy. We are constructing a Sensitive Resolved Ion Beam Spectroscopy setup which will harness the benefits of kinematic compression in a molecular ion beam to enable very high resolution spectroscopy. This ion beam is interrogated by continuous-wave cavity ringdown spectroscopy using a home-made widely tunable difference frequency laser that utilizes two near-IR lasers and a periodically-poled lithium niobate crystal. Here, we report our efforts to optimize our ion beam spectrometer and to perform high-precision and high-accuracy frequency measurements using an optical frequency comb. footnote

  3. Terahertz time-domain and Fourier-transform infrared spectroscopy of traditional Korean pigments

    NASA Astrophysics Data System (ADS)

    Hong, Taeyoon; Choi, Kyujin; Ha, Taewoo; Park, Byung Cheol; Sim, Kyung Ik; Kim, Jong Hyeon; Kim, Jae Hoon; Kwon, Jy Eun; Lee, Sanghyun; Kang, Dai Ill; Lee, Han Hyoung

    2014-03-01

    Representative traditional Korean pigments (oyster shell white [hobun], massicot [miltaseung], indigo [jjok], azurite [seokcheong], malachite [seokrok], and red lead [yeondan]) have been studied with terahertz time-domain spectroscopy (THz-TDS) and Fourier-transform infrared spectroscopy (FTIRS) over the spectral region of 0.1-7.5 THz. Both the refractive index n and the extinction coefficient k were simultaneously and independently determined in the terahertz region without a Kramers-Kronig analysis while the absoprtion coefficient spectra were acquired in the infrared region. All pigments studied in the present work exhibited a set of characteristic absorption peaks unique to the pigment species in addition to a background that increased with increasing frequency. Our study demonstrates that terahertz and infrared techniques can be useful identification and diagnostic tools for the traditional Korean pigments used in heritage buildings and artworks.

  4. Interfacial Electron Transfer and Transient Photoconductivity Studied with Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Milot, Rebecca Lee

    Terahertz spectroscopy is distinguished from other far infrared and millimeter wave spectroscopies by its inherent phase sensitivity and sub-picosecond time resolution making it a versatile technique to study a wide range of physical phenomena. As THz spectroscopy is still a relatively new field, many aspects of THz generation mechanisms have not been fully examined. Using terahertz emission spectroscopy (TES), THz emission from ZnTe(110) was analyzed and found to be limited by two-photon absorption and free-carrier generation at high excitation fluences. Due to concerns about the continued use of fossil fuels, solar energy has been widely investigated as a promising source of renewable energy. Dye-sensitized solar cells (DSSCs) have been developed as a low-cost alternative to conventional photovoltaic solar cells. To solve the issues of the intermittency and inefficient transport associated with solar energy, researchers are attempting to adapt DSSCs for water oxidation and chemical fuel production. Both device designs incorporate sensitizer molecules covalently bound to metal oxide nanoparticles. The sensitizer, which is comprised of a chromophore and anchoring group, absorbs light and transfers an electron from its excited state to the conduction band of the metal oxide, producing an electric current. Using time-resolved THz spectroscopy (TRTS), an optical pump/THz probe technique, the efficiency and dynamics of electron injection from sensitizers to metal oxides was evaluated as a function of the chromophore, its anchoring group, and the metal oxide identity. Experiments for studying fully functioning DSSCs and water oxidation devices are also described. Bio-inspired pentafluorophenyl porphyrin chromophores have been designed and synthesized for use in photoelectrochemical water oxidation cells. Influences on the efficiency and dynamics of electron injection from the chromophores into TiO2 and SnO2 nanoparticles due to changes in both the central substituent to

  5. Terahertz spectroscopy of human skin constituents in suspension

    NASA Astrophysics Data System (ADS)

    Joseph, Cecil; Yaroslavsky, Anna; Al-Arashi, Munir; Gatesman, Andrew; Goyette, Thomas; Giles, Robert

    2008-03-01

    Continuous wave terahertz imaging has the potential to offer a non-invasive medical imaging modality for detecting different types of human cancers. The aim of this study was to identify frequencies of interest for continuous wave terahertz imaging of skin cancer. The absorption characteristics of water, collagen, and elastin were studied in the range between 20 and 100cm-1. In addition, we have recorded and analyzed the teraherz absorption spectra of several substances that are present in human skin (i.e. tryptophan, tyrosine, melanin, urocanic acid, keratin) and their water suspensions with the goal of using them as biomarkers for skin cancer detection.

  6. Terahertz time-domain spectroscopy and quantitative analysis of metal gluconates.

    PubMed

    Li, Shaoxian; Yang, Jingqi; Zhao, Hongwei; Yang, Na; Jing, Dandan; Zhang, Jianbing; Li, Qingnuan; Han, Jiaguang

    2015-01-01

    A series of metal gluconates (Na(+), K(+), Mg(2+), Ca(2+), Fe(2+), Cu(2+), and Zn(2+)) were investigated by terahertz (THz) time-domain spectroscopy. The absorption coefficients and refractive indices of the samples were obtained in the frequency range of 0.5-2.6 THz. The gluconates showed distinct THz characteristic fingerprints, and the dissimilarities reflect their different structures, hydrogen-bond networks, and molecular interactions. In addition, some common features were observed among these gluconates, and the similarities probably come from the similar carbohydrate anion group. The X-ray powder diffraction measurements of these metal gluconates were performed, and the copper(II) gluconate was found to be amorphous, corresponding to the monotonic increase feature in the THz absorption spectrum. The results suggest that THz spectroscopy is sensitive to molecular structure and physical form. Binary and ternary mixtures of different gluconates were quantitatively analyzed based on the Beer-Lambert law. A chemical map of a tablet containing calcium D-gluconate monohydrate and α-lactose in the polyethylene host was obtained by THz imaging. The study shows that THz technology is a useful tool in pharmaceutical research and quality control applications. PMID:25506686

  7. TeraHertz Time Domain Spectroscopy of Astrophysical Analog Materials

    NASA Astrophysics Data System (ADS)

    Blake, Geoffrey

    The section of the electromagnetic spectrum extending roughly from wavelengths of 3 millimeters to 30 microns is commonly known as the far-infrared or TeraHertz (THz) region. It contains the great majority of the photons emitted by the universe, and THz observations of molecules and dust are able penetrate deeply into molecular clouds, thus revealing the full history of star and planet formation. Accordingly, the successful deployments of the Herschel and SOFIA observatories, and the emerging capabilities of ALMA, are both revolutionizing our understanding of THz astrophysics and placing stringent demands on the generation of accurate laboratory data on the relevant gas phase and solid state materials detected. With APRA support, we have constructed a combined high bandwidth and high spectral resolution femtosecond THz Time Domain Spectroscopy (THz TDS) system and an FT-IR spectrometer, and coupled these instruments to a high vacuum chamber and cryostat and to gas phase cells including a molecular beam system. We have investigated solid materials from room temperature to 10 K, and can examine both refractory matter such as silicates and molecular ices. For the latter, we have demonstrated that the THz bands observed are uniquely sensitive to both the molecular structure of the ice and its thermal history, and thus that THz observations can provide novel insight into the dominant condensable materials in dense, cold regions. In the gas phase we can record doppler-limited data over at least a decade in bandwidth. While quite capable, the high vacuum cryostat can only study thick samples, especially ices, due to the fairly rapid adsorption of gases onto surfaces at low temperature under such conditions. It is therefore not possible to examine highly layered/structured samples or reactive species. We therefore propose here to upgrade the chamber/cryostat to ultrahigh vacuum, and implement additional sample preparation and characterization tools. With such modifications

  8. [Aging explosive detection using terahertz time-domain spectroscopy].

    PubMed

    Meng, Kun; Li, Ze-ren; Liu, Qiao

    2011-05-01

    Detecting the aging situation of stock explosive is essentially meaningful to the research on the capability, security and stability of explosive. Existing aging explosive detection techniques, such as scan microscope technique, Fourier transfer infrared spectrum technique, gas chromatogram mass spectrum technique and so on, are either not able to differentiate whether the explosive is aging or not, or not able to image the structure change of the molecule. In the present paper, using the density functional theory (DFT), the absorb spectrum changes after the explosive aging were calculated, from which we can clearly find the difference of spectrum between explosive molecule and aging ones in the terahertz band. The terahertz time-domain spectrum (THz-TDS) system as well as its frequency spectrum resolution and measured range are analyzed. Combined with the existing experimental results and the essential characters of the terahertz wave, the application of THz-TDS technique to the detection of aging explosive was demonstrated from the aspects of feasibility, veracity and practicability. On the base of that, the authors advance the new method of aging explosive detection using the terahertz time-domain spectrum technique.

  9. Application of femtotechnologies and terahertz spectroscopy methods in cataract diagnostics

    NASA Astrophysics Data System (ADS)

    Sakhnov, S. N.; Leksutkina, E. V.; Smolyanskaya, O. A.; Usov, A. V.; Parakhuda, S. E.; Grachev, Ya. V.; Kozlov, S. A.

    2011-08-01

    We study the destructive action of femtosecond pulses (200 fs) on the human cataractous crystalline lens and the transmission of the cataractous lens in the terahertz spectral range of electromagnetic oscillations (0.2-1 THz) in relation to the density of the nucleus of the lens.

  10. Multifrequency continuous wave terahertz spectroscopy for absolute thickness determination

    SciTech Connect

    Scheller, Maik; Baaske, Kai; Koch, Martin

    2010-04-12

    We present a tunable multifrequency continuous wave terahertz spectrometer based on two laser diodes, photoconductive antennas, and a coherent detection scheme. The system is employed to determine the absolute thickness of samples utilizing a proposed synthetic difference frequency method to circumvent the 2pi uncertainty known from conventional photomixing systems while preserving a high spatial resolution.

  11. Crystallization of amorphous lactose at high humidity studied by terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    McIntosh, Alexander I.; Yang, Bin; Goldup, Stephen M.; Watkinson, Michael; Donnan, Robert S.

    2013-02-01

    We report the first use of terahertz time-domain spectroscopy (THz-TDS) to study the hydration and crystallization of an amorphous molecular solid at high humidity. Lactose in its amorphous and monohydrate forms exhibits different terahertz spectra due to the lack of long range order in the amorphous material. This difference allowed the transformation of amorphous lactose to its monohydrate form at high humidity to be studied in real time. Spectral fitting of frequency-domain data allowed kinetic data to be obtained and the crystallization was found to obey Avrami kinetics. Bulk changes during the crystallization could also be observed in the time-domain.

  12. Analysis of drugs-of-abuse and explosives using terahertz time-domain and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Burnett, Andrew; Fan, Wenhui; Upadhya, Prashanth; Cunningham, John; Linfield, Edmund; Davies, Giles; Edwards, Howell; Munshi, Tasnim; O'Neil, Andrew

    2006-02-01

    We demonstrate that, through coherent measurement of the transmitted terahertz electric fields, broadband (0.3-8THz) time-domain spectroscopy can be used to measure far-infrared vibrational modes of a range of illegal drugs and high explosives that are of interest to the forensic and security services. Our results show that these absorption features are highly sensitive to the structural and spatial arrangement of the molecules. Terahertz frequency spectra are also compared with high-resolution low-frequency Raman spectra to assist in understanding the low frequency inter- and intra-molecular vibrational modes of the molecules.

  13. Application of terahertz spectroscopy and molecular modeling in isomers investigation: Glucose and fructose

    NASA Astrophysics Data System (ADS)

    Zheng, Zhuan-Ping; Fan, Wen-Hui; Liang, Yu-Qing; Yan, Hui

    2012-04-01

    Terahertz spectra of glucose and fructose have been measured by terahertz time-domain spectroscopy (THz-TDS) at room temperature. Because they have the same molecular formula, the differences of the THz spectra can be attributed to their molecular structures and the arrangement of molecules in unit cell. In this paper, gaseous-state theory has been employed to simulate the isolated molecule of these two isomers. The results indicate that experimental THz spectral features (0.5 - 4.0 THz) of glucose and fructose arise from the mixture of intramolecular and intermolecular modes, involving hydrogen bonds and covalent bonds, and with the intermolecular modes dominating.

  14. In vivo terahertz pulsed spectroscopy of dysplastic and non-dysplastic skin nevi

    NASA Astrophysics Data System (ADS)

    Zaytsev, Kirill I.; Chernomyrdin, Nikita V.; Kudrin, Konstantin G.; Gavdush, Arseniy A.; Nosov, Pavel A.; Yurchenko, Stanislav O.; Reshetov, Igor V.

    2016-08-01

    The results of the in vivo terahertz (THz) pulsed spectroscopy (TPS) of pigmentary skin nevi are reported. Observed THz dielectric permittivity of healthy skin and dysplastic and non-dysplastic skin nevi exhibits significant contrast in THz frequency range. Dysplastic skin nevus is a precursor of melanoma, which is reportedly the most dangerous cancer of the skin. Therefore, the THz dielectric spectroscopy is potentially an effective tool for non-invasive early diagnosis of melanomas of the skin.

  15. Time-resolved single-shot terahertz time-domain spectroscopy for ultrafast irreversible processes

    NASA Astrophysics Data System (ADS)

    Zhai, Zhao-Hui; Zhong, Sen-Cheng; Li, Jun; Zhu, Li-Guo; Meng, Kun; Li, Jiang; Liu, Qiao; Peng, Qi-Xian; Li, Ze-Ren; Zhao, Jian-Heng

    2016-09-01

    Pulsed terahertz spectroscopy is suitable for spectroscopic diagnostics of ultrafast events. However, the study of irreversible or single shot ultrafast events requires ability to record transient properties at multiple time delays, i.e., time resolved at single shot level, which is not available currently. Here by angular multiplexing use of femtosecond laser pulses, we developed and demonstrated a time resolved, transient terahertz time domain spectroscopy technique, where burst mode THz pulses were generated and then detected in a single shot measurement manner. The burst mode THz pulses contain 2 sub-THz pulses, and the time gap between them is adjustable up to 1 ns with picosecond accuracy, thus it can be used to probe the single shot event at two different time delays. The system can detect the sub-THz pulses at 0.1 THz-2.5 THz range with signal to noise ratio (SNR) of ˜400 and spectrum resolution of 0.05 THz. System design was described here, and optimizations of single shot measurement of THz pulses were discussed in detail. Methods to improve SNR were also discussed in detail. A system application was demonstrated where pulsed THz signals at different time delays of the ultrafast process were successfully acquired within single shot measurement. This time resolved transient terahertz time domain spectroscopy technique provides a new diagnostic tool for irreversible or single shot ultrafast events where dynamic information can be extracted at terahertz range within one-shot experiment.

  16. Near-Field Orientation Sensitive Terahertz Micro-Spectroscopy of Single Crystals

    NASA Astrophysics Data System (ADS)

    Acbas, Gheorghe; Singh, Rohit; Snell, Edward; Markelz, Andrea

    2012-02-01

    We present spectroscopic imaging studies of molecular crystals. These measurements examine the anisotropy of the intra and inter-molecular vibrational modes of single crystals at terahertz frequencies. The method is based on the technique developed in [1-2] for sub-wavelength resolution time domain terahertz spectroscopy (THz TDS), with added polarization orientation dependent measurements and hydration control. This method allows us to study the spectroscopic properties of small single crystals with sizes down to 20 micrometers. In addition, mapping the spectroscopic information at such small spatial scales allows us to reduce the water absorption and interference artifacts that usually affect protein THz TDS measurements. We show the polarization sensitive terahertz absorption spectra in the (0.3-3THz) range of sucrose, oxalic acid and lysozyme protein crystals. *M. A. Seo, et. al., Opt. Express, 15(19):11781--11789, 09 (2007) *J. R Knab, et. al., App. Phys. Lett.,97, 031115 (2010)

  17. Emulation and design of terahertz reflection-mode confocal scanning microscopy based on virtual pinhole

    NASA Astrophysics Data System (ADS)

    Yang, Yong-fa; Li, Qi

    2014-12-01

    In the practical application of terahertz reflection-mode confocal scanning microscopy, the size of detector pinhole is an important factor that determines the performance of spatial resolution characteristic of the microscopic system. However, the use of physical pinhole brings some inconvenience to the experiment and the adjustment error has a great influence on the experiment result. Through reasonably selecting the parameter of matrix detector virtual pinhole (VPH), it can efficiently approximate the physical pinhole. By using this approach, the difficulty of experimental calibration is reduced significantly. In this article, an imaging scheme of terahertz reflection-mode confocal scanning microscopy that is based on the matrix detector VPH is put forward. The influence of detector pinhole size on the axial resolution of confocal scanning microscopy is emulated and analyzed. Then, the parameter of VPH is emulated when the best axial imaging performance is reached.

  18. Identification of Potential Estrogenic Environmental Pollutants by Terahertz Transmission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Quema, Alex; Takahashi, Hiroshi; Sakai, Masahiro; Goto, Masahiro; Ono, Shingo; Sarukura, Nobuhiko; Shioda, Ryu; Yamada, Norihide

    2003-08-01

    Using magnetically enhanced terahertz radiation from InAs, various naphthols, which exhibits estrogenic like activity and are potentially mimic natural hormones, are studied. The experimental results show that the naphthols, depicted by the position of the hydroxyl (-OH) component at different carbon atom sites of the naphthalene compound, are distinguishable based on the absorption of THz radiation. It is found that the THz radiation absorption is strongly related to the crystal symmetry and dipole moment of these isomers.

  19. Biomedical Applications of Terahertz Spectroscopy: A Brief Review

    NASA Astrophysics Data System (ADS)

    Vargas-Luna, M.; Huerta-Franco, R.

    2008-08-01

    The Terahertz (THz) window of the electromagnetic spectrum has been partially explored but almost unexploited commercially. In recent years there has been an increased interest and a technological boost in THz research for detection systems, material characterization and imaging. Among many hot topics the researchers are interested in medical applications, and protein characterization. We present a general overview of the field showing some of the handicaps and promises of this region of the electromagnetic spectrum.

  20. New terahertz dielectric spectroscopy for the study of aqueous solutions

    SciTech Connect

    George, Deepu K.; Charkhesht, Ali; Vinh, N. Q.

    2015-12-15

    We present the development of a high precision, tunable far-infrared (terahertz) frequency-domain dielectric spectrometer for studying the dynamics of biomolecules in aqueous solutions in the gigahertz-to-terahertz frequency. As an important benchmark system, we report on the measurements of the absorption and refractive index for liquid water in the frequency range from 5 GHz to 1.12 THz (0.17–37.36 cm{sup −1} or 0.268–60 mm). The system provides a coherent radiation source with power up to 20 mW in the gigahertz-to-terahertz region. The dynamic range of our instrument reaches 10{sup 12} and the system achieves a spectral resolution of less than 100 Hz. The temperature of samples can be controlled precisely with error bars of ±0.02 °C from 0 °C to 90 °C. Given these attributes, our spectrometer provides unique capabilities for the accurate measurement of even very strongly absorbing materials such as aqueous solutions.

  1. New terahertz dielectric spectroscopy for the study of aqueous solutions.

    PubMed

    George, Deepu K; Charkhesht, Ali; Vinh, N Q

    2015-12-01

    We present the development of a high precision, tunable far-infrared (terahertz) frequency-domain dielectric spectrometer for studying the dynamics of biomolecules in aqueous solutions in the gigahertz-to-terahertz frequency. As an important benchmark system, we report on the measurements of the absorption and refractive index for liquid water in the frequency range from 5 GHz to 1.12 THz (0.17-37.36 cm(-1) or 0.268-60 mm). The system provides a coherent radiation source with power up to 20 mW in the gigahertz-to-terahertz region. The dynamic range of our instrument reaches 10(12) and the system achieves a spectral resolution of less than 100 Hz. The temperature of samples can be controlled precisely with error bars of ±0.02 °C from 0 °C to 90 °C. Given these attributes, our spectrometer provides unique capabilities for the accurate measurement of even very strongly absorbing materials such as aqueous solutions.

  2. Monitoring PM2.5 in the Atmosphere by Using Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhan, Honglei; Zhao, Kun; Bao, Rima; Xiao, Lizhi

    2016-09-01

    The real-time monitoring of the air pollution with multiple sources is of great significance for pollution control and environmental protection. In this paper, we presented a study of terahertz time-domain spectroscopy (THz-TDS) as a direct tool for monitoring the component and content of PM2.5 in atmosphere. Due to the THz absorption, the intensities of the peaks in THz-TDS decreased with the augment of PM2.5 and were proportional to the PM2.5 content. The ratio of absorbance A to PM2.5 reflected a basically unchanged tendency, indicating the little change of principal elements under the pollution degree. In the high-pollution condition, a lot of SO2 from vehicle and factory was emitted into air. The elements, such as S and O from anions, had a stronger absorption effect in THz range. Based on the absorbance spectra, the absorption tendencies with PM2.5 over the whole range were validated by principal component analysis and the quantitative model with a high correlation was built by using back propagation artificial neural network. BPANN model improved the precision of linear fitting between peak intensities and PM2.5. The research demonstrates that THz-TDS is a promising tool for fast, direct, and reliable monitoring in environmental applications.

  3. Ultrafast terahertz modulation characteristic of tungsten doped vanadium dioxide nanogranular film revealed by time-resolved terahertz spectroscopy

    SciTech Connect

    Xiao, Yang; Zhai, Zhao-Hui; Zhu, Li-Guo E-mail: huangwanxia@scu.edu.cn; Li, Jun; Peng, Qi-Xian; Li, Ze-Ren; Shi, Qi-Wu; Huang, Wan-Xia E-mail: huangwanxia@scu.edu.cn; Yue, Fang; Hu, Yan-Yan

    2015-07-20

    The ultrafast terahertz (THz) modulation characteristic during photo-induced insulator-to-metal transition (IMT) of undoped and tungsten (W)-doped VO{sub 2} film was investigated at picoseconds time scale using time-resolved THz spectroscopy. W-doping slows down the photo-induced IMT dynamic processes (both the fast non-thermal process and the slow metallic phase propagation process) in VO{sub 2} film and also reduces the pump fluence threshold of photo-induced IMT in VO{sub 2} film. Along with the observed broadening of phase transition temperature window of IMT in W-doped VO{sub 2}, we conclude that W-doping prevents metallic phase domains from percolation. By further extracting carrier properties from photo-induced THz conductivity at several phase transition times, we found that the electron-electron correlation during IMT is enhanced in W-doped VO{sub 2}.

  4. [Identification of Official Rhubarb Samples by Using PLS and Terahertz Time-Domain Spectroscopy].

    PubMed

    Wang, Jing-rong; Zhang, Zhuo-yong; Zhang, Zhen-wei; Xiang, Yu-hong

    2016-02-01

    The development of terahertz technology is attracting broad intention in recent years. The quality identification is important for the quality control of Chinese medicine production. In the present work, terahertz time-domain spectroscopy (THz-TDS) combined with partial least squares (PLS) were used for the identification model building and studied based on 41 official and unofficial rhubarb samples. First, the THz-TDS spectra of rhubarb samples were collected and were preprocessed by using chemometrics methods rather than transformed to absorption spectra. The identification models were then established based on the processed terahertz time domain spectra. The spectral preprocessing methods include Savitzky-Golay (S-G) first derivative, detrending, standard normal transformation (SNV), autoscaling, and mean centering. The identification accuracy of 90% was accomplished by using proper pretreatment methods, which was higher than the classified accuracy of 80% without any preprocessing for the time domain spectra. The component number of the PLS model was evaluated by leave-one-out cross-validation (LOOCV). The minimum values of the root-mean squared error of cross-validation (RMSECV) and root-mean squared error of prediction (RMSEP) were 0.076 6 and 0.169 0 by using mean centering method, respectively. The results of this work showed that the combination of terahertz time domain spectroscopy technology with chemometrics methods, as well as PLS can be applied for the recognition of genuine and counterfeit Chinese herbal medicines, as well as official and unofficial rhubarbs. The advantage of using terahertz time domain spectra directly with no transformation into absorption spectra is: (1) the thickness of samples could not be considered in the model establishment, and (2) the spectral processing was simplified. The proposed method based on the combination of THz-TDS and chemometrics proved to be rapid, simple, non-pollution and solvent free, suitable to be

  5. [Identification of Official Rhubarb Samples by Using PLS and Terahertz Time-Domain Spectroscopy].

    PubMed

    Wang, Jing-rong; Zhang, Zhuo-yong; Zhang, Zhen-wei; Xiang, Yu-hong

    2016-02-01

    The development of terahertz technology is attracting broad intention in recent years. The quality identification is important for the quality control of Chinese medicine production. In the present work, terahertz time-domain spectroscopy (THz-TDS) combined with partial least squares (PLS) were used for the identification model building and studied based on 41 official and unofficial rhubarb samples. First, the THz-TDS spectra of rhubarb samples were collected and were preprocessed by using chemometrics methods rather than transformed to absorption spectra. The identification models were then established based on the processed terahertz time domain spectra. The spectral preprocessing methods include Savitzky-Golay (S-G) first derivative, detrending, standard normal transformation (SNV), autoscaling, and mean centering. The identification accuracy of 90% was accomplished by using proper pretreatment methods, which was higher than the classified accuracy of 80% without any preprocessing for the time domain spectra. The component number of the PLS model was evaluated by leave-one-out cross-validation (LOOCV). The minimum values of the root-mean squared error of cross-validation (RMSECV) and root-mean squared error of prediction (RMSEP) were 0.076 6 and 0.169 0 by using mean centering method, respectively. The results of this work showed that the combination of terahertz time domain spectroscopy technology with chemometrics methods, as well as PLS can be applied for the recognition of genuine and counterfeit Chinese herbal medicines, as well as official and unofficial rhubarbs. The advantage of using terahertz time domain spectra directly with no transformation into absorption spectra is: (1) the thickness of samples could not be considered in the model establishment, and (2) the spectral processing was simplified. The proposed method based on the combination of THz-TDS and chemometrics proved to be rapid, simple, non-pollution and solvent free, suitable to be

  6. Integrated injection seeded terahertz source and amplifier for time-domain spectroscopy.

    PubMed

    Maysonnave, J; Jukam, N; Ibrahim, M S M; Maussang, K; Madéo, J; Cavalié, P; Dean, P; Khanna, S P; Steenson, D P; Linfield, E H; Davies, A G; Tignon, J; Dhillon, S S

    2012-02-15

    We used a terahertz (THz) quantum cascade laser (QCL) as an integrated injection seeded source and amplifier for THz time-domain spectroscopy. A THz input pulse is generated inside a QCL by illuminating the laser facet with a near-IR pulse from a femtosecond laser and amplified using gain switching. The THz output from the QCL is found to saturate upon increasing the amplitude of the THz input power, which indicates that the QCL is operating in an injection seeded regime.

  7. Imaging molecular adsorption and desorption dynamics on graphene using terahertz emission spectroscopy.

    PubMed

    Sano, Y; Kawayama, I; Tabata, M; Salek, K A; Murakami, H; Wang, M; Vajtai, R; Ajayan, P M; Kono, J; Tonouchi, M

    2014-01-01

    Being an atomically thin material, graphene is known to be extremely susceptible to its environment, including defects and phonons in the substrate on which it is placed as well as gas molecules that surround it. Thus, any device design using graphene has to take into consideration all surrounding components, and device performance needs to be evaluated in terms of environmental influence. However, no methods have been established to date to readily measure the density and distribution of external perturbations in a quantitative and non-destructive manner. Here, we present a rapid and non-contact method for visualizing the distribution of molecular adsorbates on graphene semi-quantitatively using terahertz time-domain spectroscopy and imaging. We found that the waveform of terahertz bursts emitted from graphene-coated InP sensitively changes with the type of atmospheric gas, laser irradiation time, and ultraviolet light illumination. The terahertz waveform change is explained through band structure modifications in the InP surface depletion layer due to the presence of localized electric dipoles induced by adsorbed oxygen. These results demonstrate that terahertz emission serves as a local probe for monitoring adsorption and desorption processes on graphene films and devices, suggesting a novel two-dimensional sensor for detecting local chemical reactions. PMID:25116593

  8. Improved Tuning Fork for Terahertz Quartz-Enhanced Photoacoustic Spectroscopy

    PubMed Central

    Sampaolo, Angelo; Patimisco, Pietro; Giglio, Marilena; Vitiello, Miriam S.; Beere, Harvey E.; Ritchie, David A.; Scamarcio, Gaetano; Tittel, Frank K.; Spagnolo, Vincenzo

    2016-01-01

    We report on a quartz-enhanced photoacoustic (QEPAS) sensor for methanol (CH3OH) detection employing a novel quartz tuning fork (QTF), specifically designed to enhance the QEPAS sensing performance in the terahertz (THz) spectral range. A discussion of the QTF properties in terms of resonance frequency, quality factor and acousto-electric transduction efficiency as a function of prong sizes and spacing between the QTF prongs is presented. The QTF was employed in a QEPAS sensor system using a 3.93 THz quantum cascade laser as the excitation source in resonance with a CH3OH rotational absorption line located at 131.054 cm−1. A minimum detection limit of 160 ppb in 30 s integration time, corresponding to a normalized noise equivalent absorption NNEA = 3.75 × 10−11 cm−1W/Hz½, was achieved, representing a nearly one-order-of-magnitude improvement with respect to previous reports. PMID:27023552

  9. Thin film polycrystalline Si solar cells studied in transient regime by optical pump-terahertz probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Pikna, P.; Skoromets, V.; Becker, C.; Fejfar, A.; Kužel, P.

    2015-12-01

    We used time-resolved terahertz spectroscopy to study ultrafast photoconductivity of polycrystalline thin-film silicon solar cells. We selected a series of samples, which exhibited variable conversion efficiencies due to hydrogen plasma passivation under various technological conditions. The decay of the transient terahertz conductivity shows two components: the fast one is related to the charge recombination at interfaces, while the slow nanosecond one is attributed to the trapping of photocarriers by defects localized at grain boundaries or at dislocations in the polycrystalline p- layer of the structure. We observed a clear correlation between the open-circuit voltage and the nanosecond-scale decay time of the transient terahertz conductivity of the solar cells. Thus, the terahertz spectroscopy appears to be a useful contactless tool for inspecting the local photoconductivity of solar cells including, in particular, various nanostructured schemes.

  10. Characteristic responses of biological and nanoscale systems in the terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Angeluts, A. A.; Balakin, A. V.; Evdokimov, M. G.; Esaulkov, M. N.; Nazarov, M. M.; Ozheredov, I. A.; Sapozhnikov, D. A.; Solyankin, P. M.; Cherkasova, O. P.; Shkurinov, A. P.

    2014-07-01

    This paper briefly examines methods for the generation of pulsed terahertz radiation and principles of pulsed terahertz spectroscopy, an advanced informative method for studies of complex biological and nanostructured systems. Some of its practical applications are described. Using a number of steroid hormones as examples, we demonstrate that terahertz spectroscopy in combination with molecular dynamics methods and computer simulation allows one to gain information about the structure of molecules in crystals. A 'terahertz colour vision' method is proposed for analysis of pulsed terahertz signals reflected from biological tissues and it is shown that this method can be effectively used to analyse the properties of biological tissues and for early skin cancer diagnosis.

  11. Linearity of Air-Biased Coherent Detection for Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Tianwu; Iwaszczuk, Krzysztof; Wrisberg, Emil Astrup; Denning, Emil Vosmar; Jepsen, Peter Uhd

    2016-06-01

    The performance of air-biased coherent detection (ABCD) in a broadband two-color laser-induced air plasma system for terahertz time-domain spectroscopy (THz-TDS) has been investigated. Fundamental parameters of the ABCD detection, including signal-to-noise ratio (SNR), dynamic range (DR), and linearity of detection have been characterized. Moreover, the performance of a photomultiplier tube (PMT) and an avalanche photodiode (APD) as photodetector in the ABCD have been compared. We have observed nonlinear behavior of PMT detector, which leads to artificial gain factor in TDS spectroscopy. The APD turns out to have superior linearity and three times higher dynamic compared to the PMT.

  12. Ultrafast multi-terahertz nano-spectroscopy with sub-cycle temporal resolution

    NASA Astrophysics Data System (ADS)

    Eisele, M.; Cocker, T. L.; Huber, M. A.; Plankl, M.; Viti, L.; Ercolani, D.; Sorba, L.; Vitiello, M. S.; Huber, R.

    2014-11-01

    Phase-locked ultrashort pulses in the rich terahertz spectral range have provided key insights into phenomena as diverse as quantum confinement, first-order phase transitions, high-temperature superconductivity and carrier transport in nanomaterials. Ultrabroadband electro-optic sampling of few-cycle field transients can even reveal novel dynamics that occur faster than a single oscillation cycle of light. However, conventional terahertz spectroscopy is intrinsically restricted to ensemble measurements by the diffraction limit. As a result, it measures dielectric functions averaged over the size, structure, orientation and density of nanoparticles, nanocrystals or nanodomains. Here, we extend ultrabroadband time-resolved terahertz spectroscopy to the sub-nanoparticle scale (10 nm) by combining sub-cycle, field-resolved detection (10 fs) with scattering-type near-field scanning optical microscopy (s-NSOM). We trace the time-dependent dielectric function at the surface of a single photoexcited InAs nanowire in all three spatial dimensions and reveal the ultrafast (<50 fs) formation of a local carrier depletion layer.

  13. Study on spectral properties of difenoconazole by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhou, Qian; Liu, Ying; Kou, Kuan; Zhao, Guozhong

    2015-08-01

    The terahertz (THz) and infrared spectra of solid pesticide difenoconazole are studied. The absorption spectra of difenoconazole are obtained at room temperature in the frequency range of 0.2 THz - 2.6 THz by using of terahertz time-domain spectroscopy (THz-TDS) and in the frequency range of 1.8 THz - 10 THz by the Fourier Transform Infrared Spectroscopy (FTIR). The experimental results show five significant absorption peaks in THz frequency range, respectively, 0.66 T, 0.80 T, 1.03 T, 1.31 T and 1.57 T, and those peaks corresponding to the abnormal dispersion. The spectral characteristics between 0.2 THz and 15 THz of difenoconazole are simulated by using of Gaussian03 software based on the single molecular model and the density functional theory (DFT). Both of simulation and experimental results fit well in the terahertz range. Moreover, the quantitative analysis of difenoconazole is studied based on the THz-TDS measurement. The absorption coefficient and refractive index spectra of difenoconazoles at different proportions doped with polyethylene (PE) are obtained. The partial least squares (PLS) model is built. It is possible to predict the concentration of difenoconazole in the mixtures by this method.

  14. [Preliminary research on insect damage detection in pecans using terahertz spectroscopy].

    PubMed

    Li, Bin; Wang, Ning; Zhang, Wei-Li; Zhao, Chun-Jiang; Zhang, Bao-Hua

    2014-05-01

    Pecan is an important nut in US, however, the inner insect influences pecan's quality a lot. To realize the nondestructive detection of insect damage in American pecans rapidly and efficiently, preliminary research on insect damage detection in pecans was conducted based on terahertz spectroscopy. Firstly, a set of native pecan nuts were collected and were manually sliced with a thickness of about 1, 2 and 3 mm and with a size of about 2 cm(length) X 1 cm(width) for every pecan nutmeat; Pecan shell and inner separator were also cut into the same size. Secondly, the absorption spectra of the nutmeat slices, shell, and inner separator were collected using THz time-domain spectroscopy (THz-TDS) developed by a group of researchers at Oklahoma State University, and the spectral characteristic of the slices was analyzed. Thirdly, the absorption spectra of the alive manduca sexta and dry pecan weevil were collected, and due to the high contents in the insects, very obvious spectral characteristics were found. Finally, the transmission experiment was conducted with the whole pecans. The results from the preliminary study show a potential application of THz technology for insect damage detection. This research provides a reference for further understanding terahertz and exploring sample preparation methods, test methods, data acquisition and optical parameters calculation methods, and developing nondestructive detection system for insect damage in American pecans based on terahertz technology.

  15. [Preliminary research on insect damage detection in pecans using terahertz spectroscopy].

    PubMed

    Li, Bin; Wang, Ning; Zhang, Wei-Li; Zhao, Chun-Jiang; Zhang, Bao-Hua

    2014-05-01

    Pecan is an important nut in US, however, the inner insect influences pecan's quality a lot. To realize the nondestructive detection of insect damage in American pecans rapidly and efficiently, preliminary research on insect damage detection in pecans was conducted based on terahertz spectroscopy. Firstly, a set of native pecan nuts were collected and were manually sliced with a thickness of about 1, 2 and 3 mm and with a size of about 2 cm(length) X 1 cm(width) for every pecan nutmeat; Pecan shell and inner separator were also cut into the same size. Secondly, the absorption spectra of the nutmeat slices, shell, and inner separator were collected using THz time-domain spectroscopy (THz-TDS) developed by a group of researchers at Oklahoma State University, and the spectral characteristic of the slices was analyzed. Thirdly, the absorption spectra of the alive manduca sexta and dry pecan weevil were collected, and due to the high contents in the insects, very obvious spectral characteristics were found. Finally, the transmission experiment was conducted with the whole pecans. The results from the preliminary study show a potential application of THz technology for insect damage detection. This research provides a reference for further understanding terahertz and exploring sample preparation methods, test methods, data acquisition and optical parameters calculation methods, and developing nondestructive detection system for insect damage in American pecans based on terahertz technology. PMID:25095406

  16. Characterization of plasma treated surfaces for food safety by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Sulovská, Kateřina; Lehocký, Marián.

    2014-10-01

    A physico-chemical approach to modify surfaces not only for use in medicine, but also for preservation of food is nowadays widely studied to lower the risks of increased number of bacterial pathogens that are in a direct contact with people. Food safety is very important part of preserving sustainability during crises, especially after the enterohaemorrhagic Escherichia coli outbreak in Europe in 2011. One of the possibility how we can protect food against various pathogens is the modification of packing materials that are directly in contact with preserved food. This contribution deals with the characterization of modified surfaces with antibacterial properties via Terahertz spectroscopy. For the purpose of this paper, three monomers were used for grafting onto air radiofrequency plasma activated low density polyethylene surface, which created a brush-like structure. Next, the antibacterial agents, Irgasan and Chlorhexidine, were anchored to these surfaces. These antibacterial agents were selected for supposed effect on two most frequently occurring bacterial strains - Escherichia coli and Staphylococcus aureus. Materials were further tested for the presence of antibacterial agent molecules, in our case by means of terahertz spectroscopy. Each material was tested on two spectroscopes - the SPECTRA and the OSCAT terahertz instruments.

  17. Optical parameter determination of seed oil with terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Jiu-sheng; Zhao, Xiao-li; Xu, Degeng

    2009-07-01

    The spectral characteristics of corn oil after five minutes and ten minutes of boiling in the rang from 0.2THz to 1.5THz have been measured with THz time-domain spectroscopy (THz-TDS) at room temperature in nitrogen atmosphere. A novel iterative algorithm is employed to determinate the optical properties considering the effect of the cuvette. The refractive indices of the two corn oil samples show slow a decrease as the terahertz wave frequency increases. The power absorption coefficients increase as the frequency increases within the investigated terahertz wave frequency range. The results provided in this paper will help us to study the THz application to seed oil quality and safety detection further.

  18. Experimental study on identifying main component in rice bran oil with terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Jiu-sheng; Zhao, Xiao-li; Li, Jian-rui

    2009-07-01

    The absorption spectra of rice bran oil in the frequency range of 0.2~1.6THz has been measured with terahertz timedomain spectroscopy (THz-TDS) at room temperature in nitrogen atmosphere. It is found that hexadecanoidc acid and octadecanoic acid contained in rice bran oil has the spectral response to terahertz waves in this frequency region. Simultaneously, the corresponding theoretical spectra were given by using DFT methods with the aid of Gaussian03. The experimental spectra are well comparable with the calculated spectra and these results mutually validated both approaches. It was found that the absorption peaks of the two molecules obtained by theoretical were in good agreement with the experimental results. The research results prove the feasibility of applying THz-TDS technique to detect and identify of main component of edible oil. Furthermore, the result s provided in this paper will help us to study the THz application to food quality evaluation or safety inspection further.

  19. Application of terahertz time-domain spectroscopy technology on cosmetics testing

    NASA Astrophysics Data System (ADS)

    Jia, Xinfeng; Yu, Bin; Zhao, Guozhong; Zhang, Cunlin

    2008-03-01

    As a new technology, the terahertz technology had made a great progress in security inspection and medical field. This paper shows the application of the terahertz time-domain spectroscopy (THz-TDS) technology on cosmetic testing. We obtain the THz spectra of three kinds of usual cosmetics powders. Two kind of powder have an obvious absorption peak at 1.14 THz, but the third one has no absorption peak. The positions of absorption peaks in the infrared spectra of three kinds of powders are approximately identical. These results show that THz-TDS technology has the advantage and potential application on the cosmetic testing. In addition, we also measure some solid and liquid cosmetic components, such as Titanium-dioxide, Magnesium Stearate, Kaolin, Glycerol, etc. THz spectra of their refractive index and absorption coefficient are obtained experimentally. We are trying to establish the fingerprint spectra database of cosmetic components for further research and application.

  20. Terahertz spectroscopy of low-dimensional nanomaterials: nonlinear emission and ultrafast electrodynamics

    NASA Astrophysics Data System (ADS)

    Luo, Liang; Wang, Jigang

    2015-08-01

    Nonlinear and non-equilibrium properties of low-dimensional quantum materials are fundamental in nanoscale science yet transformative in nonlinear imaging/photonic technology today. These have been poorly addressed in many nano-materials despite of their well-established equilibrium optical and transport properties. The development of ultrafast terahertz (THz) sources and nonlinear spectroscopy tools facilitates understanding these issues and reveals a wide range of novel nonlinear and quantum phenomena that are not expected in bulk solids or atoms. In this paper, we discuss our recent discoveries in two model photonic and electronic nanostructures to solve two outstanding questions: (1) how to create nonlinear broadband terahertz emitters using deeply subwavelength nanoscale meta-atom resonators? (2) How to access one-dimensional (1D) dark excitons and their non-equilibrium correlated states in single-walled carbon nanotubes (SWMTs)?

  1. Terahertz Spectroscopy of Low-Dimensional Nanomaterials: Nonlinear Emission and Ultrafast Electrodynamics

    DOE PAGESBeta

    Luo, Liang; Wang, Jigang

    2016-01-01

    Nonlinear and non-equilibrium properties of low-dimensional quantum materials are fundamental in nanoscale science yet transformative in nonlinear imaging/photonic technology today. These have been poorly addressed in many nano-materials despite of their well-established equilibrium optical and transport properties. The development of ultrafast terahertz (THz) sources and nonlinear spectroscopy tools facilitates understanding these issues and reveals a wide range of novel nonlinear and quantum phenomena that are not expected in bulk solids or atoms. In this paper, we discuss our recent discoveries in two model photonic and electronic nanostructures to solve two outstanding questions: (1) how to create nonlinear broadband terahertz emittersmore » using deeply subwavelength nanoscale meta-atom resonators? (2) How to access one-dimensional (1D) dark excitons and their non-equilibrium correlated states in single-walled carbon nanotubes (SWMTs)?« less

  2. Low-frequency dynamics of aqueous alkali chloride solutions as probed by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Kann, Z. R.; Skinner, J. L.

    2016-06-01

    Terahertz (far infrared) spectroscopy provides a useful tool for probing both ionic motions in solution and the effect of ionic solutes on the dynamics of the solvent. In this study, we calculate terahertz spectra of aqueous alkali chloride solutions using classical but novel (the water model includes three-body interactions, the ion parameterization is non-standard, and the dipole surface is polarizable) molecular dynamics simulations. The calculated spectra compare reasonably well to experimental spectra. Decomposition of the calculated spectra is used to gain a deeper understanding of the physical phenomena underlying the spectra and the connection to, for instance, the vibrational density of states for the ions. The decomposed results are also used to explain many of the cation-dependent trends observed in the experimental spectra.

  3. Terahertz Spectroscopy of Low-Dimensional Nanomaterials: Nonlinear Emission and Ultrafast Electrodynamics

    SciTech Connect

    Luo, Liang; Wang, Jigang

    2016-01-01

    Nonlinear and non-equilibrium properties of low-dimensional quantum materials are fundamental in nanoscale science yet transformative in nonlinear imaging/photonic technology today. These have been poorly addressed in many nano-materials despite of their well-established equilibrium optical and transport properties. The development of ultrafast terahertz (THz) sources and nonlinear spectroscopy tools facilitates understanding these issues and reveals a wide range of novel nonlinear and quantum phenomena that are not expected in bulk solids or atoms. In this paper, we discuss our recent discoveries in two model photonic and electronic nanostructures to solve two outstanding questions: (1) how to create nonlinear broadband terahertz emitters using deeply subwavelength nanoscale meta-atom resonators? (2) How to access one-dimensional (1D) dark excitons and their non-equilibrium correlated states in single-walled carbon nanotubes (SWMTs)?

  4. Low-frequency dynamics of aqueous alkali chloride solutions as probed by terahertz spectroscopy.

    PubMed

    Kann, Z R; Skinner, J L

    2016-06-21

    Terahertz (far infrared) spectroscopy provides a useful tool for probing both ionic motions in solution and the effect of ionic solutes on the dynamics of the solvent. In this study, we calculate terahertz spectra of aqueous alkali chloride solutions using classical but novel (the water model includes three-body interactions, the ion parameterization is non-standard, and the dipole surface is polarizable) molecular dynamics simulations. The calculated spectra compare reasonably well to experimental spectra. Decomposition of the calculated spectra is used to gain a deeper understanding of the physical phenomena underlying the spectra and the connection to, for instance, the vibrational density of states for the ions. The decomposed results are also used to explain many of the cation-dependent trends observed in the experimental spectra. PMID:27334173

  5. Investigating the use of terahertz pulsed time domain reflection imaging for the study of fabric layers of an Egyptian mummy

    NASA Astrophysics Data System (ADS)

    Fukunaga, K.; Cortes, E.; Cosentino, A.; Stã¼nkel, I.; Leona, M.; Duling, N.; Mininberg, D. T.

    2011-08-01

    This paper reports the first use of terahertz time domain reflection imaging involving textiles on part of a complete human mummy, still in original wrapping. X-ray technique has been used extensively to investigate anatomical features, since X-ray pass through the wrapping. Terahertz waves, on the other hand, can penetrate into non-metallic materials and its reflection depends on the refractive index of materials at the interface, such as textiles and the air. The mummy of Kharushere (ca. 945-712 B.C.) was examined by using Terahertz time domain reflection imaging in the Egyptian galleries of The Metropolitan Museum of Art. Experimental results suggest that the Terahetz imaging is a promising technique for probing the fabric layers surrounding Egyptian mummies, although it is still very limited in its current state. In the future it could become a useful complement to CT scanning when materials with low radiographic density and contrast are being investigated

  6. Transmission and reflection of terahertz plasmons in two-dimensional plasmonic devices

    DOE PAGESBeta

    Sydoruk, Oleksiy; Choonee, Kaushal; Dyer, Gregory Conrad

    2015-03-10

    We found that plasmons in two-dimensional semiconductor devices will be reflected by discontinuities, notably, junctions between gated and non-gated electron channels. The transmitted and reflected plasmons can form spatially- and frequency-varying signals, and their understanding is important for the design of terahertz detectors, oscillators, and plasmonic crystals. Using mode decomposition, we studied terahertz plasmons incident on a junction between a gated and a nongated channel. The plasmon reflection and transmission coefficients were found numerically and analytically and studied between 0.3 and 1 THz for a range of electron densities. At higher frequencies, we could describe the plasmons by a simplifiedmore » model of channels in homogeneous dielectrics, for which the analytical approximations were accurate. At low frequencies, however, the full geometry and mode spectrum had to be taken into account. Moreover, the results agreed with simulations by the finite-element method. As a result, mode decomposition thus proved to be a powerful method for plasmonic devices, combining the rigor of complete solutions of Maxwell's equations with the convenience of analytical expressions.« less

  7. Transmission and reflection of terahertz plasmons in two-dimensional plasmonic devices

    SciTech Connect

    Sydoruk, Oleksiy; Choonee, Kaushal; Dyer, Gregory Conrad

    2015-03-10

    We found that plasmons in two-dimensional semiconductor devices will be reflected by discontinuities, notably, junctions between gated and non-gated electron channels. The transmitted and reflected plasmons can form spatially- and frequency-varying signals, and their understanding is important for the design of terahertz detectors, oscillators, and plasmonic crystals. Using mode decomposition, we studied terahertz plasmons incident on a junction between a gated and a nongated channel. The plasmon reflection and transmission coefficients were found numerically and analytically and studied between 0.3 and 1 THz for a range of electron densities. At higher frequencies, we could describe the plasmons by a simplified model of channels in homogeneous dielectrics, for which the analytical approximations were accurate. At low frequencies, however, the full geometry and mode spectrum had to be taken into account. Moreover, the results agreed with simulations by the finite-element method. As a result, mode decomposition thus proved to be a powerful method for plasmonic devices, combining the rigor of complete solutions of Maxwell's equations with the convenience of analytical expressions.

  8. Exploiting total internal reflection geometry for efficient optical modulation of terahertz light

    NASA Astrophysics Data System (ADS)

    Liu, Xudong; Parrott, Edward P. J.; Ung, Benjamin S.-Y.; Pickwell-MacPherson, Emma

    2016-10-01

    Efficient methods to modulate terahertz (THz) light are essential for realizing rapid THz imaging and communication applications. Here we report a novel THz modulator which utilizes the evanescent wave in a total internal reflection setup coupled with a conductive interface to enhance the attenuation efficiency of THz light. This approach makes it possible to achieve close to 100% modulation with a small interface conductivity of 12 mS. The frequency dependence of this technique is linked to the optical properties of the materials: a material with close to frequency independent conductivity that is also controllable will result in an achromatic modulation response, and the device performance can be optimized further by tuning the internal reflection angle. In this work, we focus on applying the technique in the terahertz frequency range. Using an LED array with a pump intensity of 475 mW/cm2 to produce carriers in a silicon wafer, we have achieved a modulation depth of up to 99.9% in a broad frequency range of 0.1 THz-0.8 THz. The required pumping power for the generation of the required free carriers is low because the sheet conductivity needed is far less than required for traditional transmission techniques. Consequently, the device can be modulated by an LED making it a very practical, low cost, and scalable solution for THz modulation.

  9. [The error analysis and experimental verification of laser radar spectrum detection and terahertz time domain spectroscopy].

    PubMed

    Liu, Wen-Tao; Li, Jing-Wen; Sun, Zhi-Hui

    2010-03-01

    Terahertz waves (THz, T-ray) lie between far-infrared and microwave in electromagnetic spectrum with frequency from 0.1 to 10 THz. Many chemical agent explosives show characteristic spectral features in the terahertz. Compared with conventional methods of detecting a variety of threats, such as weapons and chemical agent, THz radiation is low frequency and non-ionizing, and does not give rise to safety concerns. The present paper summarizes the latest progress in the application of terahertz time domain spectroscopy (THz-TDS) to chemical agent explosives. A kind of device on laser radar detecting and real time spectrum measuring was designed which measures the laser spectrum on the bases of Fourier optics and optical signal processing. Wedge interferometer was used as the beam splitter to wipe off the background light and detect the laser and measure the spectrum. The result indicates that 10 ns laser radar pulse can be detected and many factors affecting experiments are also introduced. The combination of laser radar spectrum detecting, THz-TDS, modern pattern recognition and signal processing technology is the developing trend of remote detection for chemical agent explosives. PMID:20496663

  10. Sensitize hydration shells of ions by the dynamics of water with terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    George, Deepu; Rahmani, John; Nguyen, Vinh

    2014-03-01

    Comparison of the relaxation dynamics of water in bulk state to that in a confined state is of significant importance to the study of interaction of biomolecules with its environment. In relation to this, the ability of terahertz dielectric spectroscopy to probe intermolecular dynamics has been explored in the past decade to look at the dynamics of water molecules which forms a hydration shell around proteins. The change in dynamics of water when its molecules interact with different types of solute molecules forms the basis of water- bio-molecular interaction. There have been several studies in the past looking at the effects of ion interactions with water molecules. In this study we have employed a vector network analyzer based terahertz dielectric spectrometer operating over the frequency range from 0.5 GHz to 1.1 THz to examine the water dynamics in several alkali metal chloride solutions. The terahertz dielectric response of these solutions as a function of concentration as well as the ion size has been studied. We have confirmed that for all these solutions the dynamics can be best described by a three Debye relaxation process of water. The relaxation times does not seem to depend on salt concentrations but on the other hand strength of relaxation modes is dependent on the molarity.

  11. [The error analysis and experimental verification of laser radar spectrum detection and terahertz time domain spectroscopy].

    PubMed

    Liu, Wen-Tao; Li, Jing-Wen; Sun, Zhi-Hui

    2010-03-01

    Terahertz waves (THz, T-ray) lie between far-infrared and microwave in electromagnetic spectrum with frequency from 0.1 to 10 THz. Many chemical agent explosives show characteristic spectral features in the terahertz. Compared with conventional methods of detecting a variety of threats, such as weapons and chemical agent, THz radiation is low frequency and non-ionizing, and does not give rise to safety concerns. The present paper summarizes the latest progress in the application of terahertz time domain spectroscopy (THz-TDS) to chemical agent explosives. A kind of device on laser radar detecting and real time spectrum measuring was designed which measures the laser spectrum on the bases of Fourier optics and optical signal processing. Wedge interferometer was used as the beam splitter to wipe off the background light and detect the laser and measure the spectrum. The result indicates that 10 ns laser radar pulse can be detected and many factors affecting experiments are also introduced. The combination of laser radar spectrum detecting, THz-TDS, modern pattern recognition and signal processing technology is the developing trend of remote detection for chemical agent explosives.

  12. Quantitative analysis of the mixtures of illicit drugs using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Jiang, Dejun; Zhao, Shusen; Shen, Jingling

    2008-03-01

    A method was proposed to quantitatively inspect the mixtures of illicit drugs with terahertz time-domain spectroscopy technique. The mass percentages of all components in a mixture can be obtained by linear regression analysis, on the assumption that all components in the mixture and their absorption features be known. For illicit drugs were scarce and expensive, firstly we used common chemicals, Benzophenone, Anthraquinone, Pyridoxine hydrochloride and L-Ascorbic acid in the experiment. Then illicit drugs and a common adulterant, methamphetamine and flour, were selected for our experiment. Experimental results were in significant agreement with actual content, which suggested that it could be an effective method for quantitative identification of illicit drugs.

  13. Label-free monitoring of interaction between DNA and oxaliplatin in aqueous solution by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Wu, Xiaojun; E, Yiwen; Xu, Xinlong; Wang, Li

    2012-07-01

    We demonstrated the feasibility of applying terahertz time-domain spectroscopy (THz-TDS) to monitor the molecular reactions in aqueous solutions of anticancer drug oxaliplatin with λ-DNA and macrophages DNA. The reaction time dependent refractive index and absorption coefficient were extracted and analyzed. The reaction half-decaying time of about 4.0 h for λ-DNA and 12.9 h for M-DNA was established. The results suggest that the THz-TDS detection could be an effective label-free technique to sense the molecular reaction in aqueous solutions and could be very useful in biology, medicine, and pharmacy industry.

  14. Vibrational frequencies of anti-diabetic drug studied by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Du, S. Q.; Li, H.; Xie, L.; Chen, L.; Peng, Y.; Zhu, Y. M.; Li, H.; Dong, P.; Wang, J. T.

    2012-04-01

    By using terahertz time-domain spectroscopy, the absorption spectra of seven anti-diabetic pills have been investigated. For gliquidone, glipizide, gliclazide, and glimepiride, an obvious resonance peak is found at 1.37 THz. Furthermore, to overcome the limit of density functional theory that can analyze the normal mode frequencies of the ground state of organic material, we also present a method that relies on pharmacophore recognition, from which we can obtain the resonance peak at 1.37 THz can be attributed to the vibration of sulfonylurea group. The results indicate that the veracity of density functional theory can be increased by combining pharmacophore recognition.

  15. Regional spectroscopy of paraffin-embedded breast cancer tissue using pulsed terahertz transmission imaging

    NASA Astrophysics Data System (ADS)

    Bowman, Tyler; El-Shenawee, Magda; Campbell, Lucas

    2016-03-01

    This work seeks to obtain the properties of paraffin-embedded breast cancer tumor tissues using transmission imaging and spectroscopy. Formalin-fixed and paraffin-embedded breast tumors are first sectioned into slices of 20 μm and 30 μm and placed between two tsurupica slides. The slides are then scanned in a pulsed terahertz system using transmission imaging. The tissue regions in adjacent pathology section are compared to the transmission imaging scan in order to define a region of points over which to average the electrical properties results from the scan.

  16. Investigation of thermal denaturation of solid oxytocin by terahertz dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Xiangjun; Yang, Xiaojie; Liu, Jianjun; Du, Yong; Hong, Zhi

    2014-07-01

    We investigate the thermal denaturation of solid oxytocin using terahertz time domain spectroscopy(THz-TDS). When the peptide is heated up from 25°C to 107°C and cooled down to 25°C again, an irreversible decrease in its THz absorption coefficient and refractive index is observed. The corresponding frequency-dependent permittivity during heating is fitted by the Debye model with single relaxation time. The relaxation times during temperature rising agree very well with Arrhenius equation with the activation energy of 3.12kJ/(K•mol) as an indicator for its thermal denaturation difficulty.

  17. Multichannel terahertz time-domain spectroscopy system at 1030 nm excitation wavelength.

    PubMed

    Brahm, Anika; Wilms, Annika; Dietz, Roman J B; Göbel, Thorsten; Schell, Martin; Notni, Gunther; Tünnermann, Andreas

    2014-06-01

    We present Terahertz (THz) imaging with a 1D multichannel time-domain spectroscopy (TDS) system which operates with a photoconductive array of 15 detection channels excited by a 1030 nm femtosecond fiber laser. The emitter and detector are photoconductive antennas based on InGaAs/InAlAs multi-layer heterostructures (MLHS). We characterized the THz optics and the resolution of the system. The performance is demonstrated by the multichannel imaging of two samples. A simultaneous measurement of 15 THz pulses with a pixel pitch of 1 mm increases the measurement speed of the TDS system by factor 15. PMID:24921495

  18. Simultaneous composition and thickness measurement of paper using terahertz time-domain spectroscopy.

    PubMed

    Mousavi, Payam; Haran, Frank; Jez, David; Santosa, Fadil; Dodge, John Steven

    2009-11-20

    We present a noncontact method for quantitative composition and thickness monitoring of flat sheet products using terahertz time-domain spectroscopy. We apply the method to obtain simultaneous measurement of thickness and moisture content of paper sheets. The paper is modeled as an effective medium of water mixed with fibers, and model parameters are estimated from fits to the measured transmission amplitude. We demonstrate the method on two different paper samples and obtain uncertainties that are comparable with existing sensor technology. Monte Carlo simulations indicate that these uncertainties can be reduced further by at least an order of magnitude. PMID:19935977

  19. In-vitro terahertz spectroscopy of rat skin under the action of dehydrating agents

    NASA Astrophysics Data System (ADS)

    Kolesnikov, Aleksandr S.; Kolesnikova, Ekaterina A.; Tuchina, Daria K.; Terentyuk, Artem G.; Nazarov, Maxim; Skaptsov, Alexander A.; Shkurinov, Alexander P.; Tuchin, Valery V.

    2014-01-01

    In the paper we present the results of study of rat skin and rat subcutaneous tumor under the action of dehydrating agents in terahertz (THz) range (15-30 THz). Frustrated Total Internal Reflection (FTIR) spectra were obtained with infrared Fourier spectrometer Nicolet 6700 and then they were recalculated in the transmittance spectra with Omnic software. Experiments were carried out with healthy and xenografted tumor in skin tissue in vitro. As the dehydrating agents 100% glycerol, 40%-water glucose solution, PEG-600, and propylene glycol were used. To determine the effect of the optical clearing agent (OCA), the alterations of terahertz transmittance for the samples were analyzed. The results have shown that PEG-600 and 40%-glucose water solution are the most effective dehydrating agent. The transmittance of healthy skin after PEG-600 application increased approximately by 6% and the transmittance of tumor tissue after PEG- 600 and 40%-glucose water solution application increased approximately by 8%. Obtained data can be useful for further application of terahertz radiation for tumor diagnostics.

  20. In vivo spectroscopy of healthy skin and pathology in terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Zaytsev, Kirill I.; Kudrin, Konstantin G.; Reshetov, Igor V.; Gavdush, Arseniy A.; Chernomyrdin, Nikita V.; Karasik, Valeriy E.; Yurchenko, Stanislav O.

    2015-01-01

    Biomedical applications of terahertz (THz) technology and, in particular, THz pulsed spectroscopy have attracted considerable interest in the scientific community. A lot of papers have been dedicated to studying the ability for human disease diagnosis, including the diagnosis of human skin cancers. In this paper we have studied the THz material parameters and THz dielectric properties of human skin and pathology in vivo, and THz pulsed spectroscopy has been utilized for this purpose. We have found a contrast between material parameters of basal cell carcinoma and healthy skin, and we have also compared the THz material parameters of dysplastic and non-dysplastic pigmentary nevi in order to study the ability for early melanoma diagnosis. Significant differences between the THz material parameters of healthy skin and pathology have been detected, thus, THz pulsed spectroscopy promises to be become an effective tool for non-invasive diagnosis of skin neoplasms.

  1. Soft tissue differentiation by diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zam, Azhar; Stelzle, Florian; Nkenke, Emeka; Tangermann-Gerk, Katja; Schmidt, Michael; Adler, Werner; Douplik, Alexandre

    2009-07-01

    Laser surgery gives the possibility to work remotely which leads to high precision, little trauma and high level sterility. However these advantages are coming with the lack of haptic feedback during the laser ablation of tissue. Therefore additional means are required to control tissue-specific ablation during laser surgery supporting the surgeon regardless of experience and skills. Diffuse Reflectance Spectroscopy provides a straightforward and simple approach for optical tissue differentiation. We measured diffuse reflectance from four various tissue types ex vivo. We applied Linear Discriminant Analysis (LDA) to differentiate the four tissue types and computed the area under the ROC curve (AUC). Special emphasis was taken on the identification of nerve as the most crucial tissue for maxillofacial surgery. The results show a promise for differentiating soft tissues as guidance for tissue-specific laser surgery by means of the diffuse reflectance.

  2. Excitation of plasmonic terahertz photovoltaic effects in a periodic two-dimensional electron system by the attenuated total reflection method

    SciTech Connect

    Fateev, D. V. Mashinsky, K. V.; Bagaeva, T. Yu.; Popov, V. V.

    2015-01-15

    The problem of the rectification of terahertz radiation due to plasmonic nonlinearities in a periodic two-dimensional electron system upon the excitation of plasma oscillations by the attenuated total reflection method is solved. This model allows the independent study of different plasmonic rectification mechanisms, i.e., plasmonic electron drag and plasmonic ratchet effects.

  3. Analysis of blood plasma at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Cherkasova, O. P.; Nazarov, M. M.; Angeluts, A. A.; Shkurinov, A. P.

    2016-01-01

    Terahertz time-domain spectroscopy in the 0.05-2.5 THz frequency range was employed to analyze blood plasma samples obtained from laboratory animals with experimental diabetes and from healthy controls. It was found that transmission and reflection coefficients of samples from rats with diabetes differed significantly from control values in both amplitude and phase. The cause of the detected differences is discussed with respect to variation in the terahertz response of water.

  4. Insulin amyloid fibrillation studied by terahertz spectroscopy and other biophysical methods

    SciTech Connect

    Liu, Rui; He, Mingxia; Su, Rongxin; Yu, Yanjun; Qi, Wei; He, Zhimin

    2010-01-01

    Assembly and fibrillation of amyloid proteins are believed to play a key role in the etiology of various human diseases, including Alzheimer's, Parkinson's, Huntington's and type II diabetes. Insights into conformational changes and formation processes during amyloid fibrillation are essential for the clinical diagnosis and drug discovery. To study the changes in secondary, tertiary, quaternary structures, and the alteration in the collective vibrational mode density of states during the amyloid fibrillation, bovine insulin in 20% acetic acid was incubated at 60 {sup o}C, and its multi-level structures were followed by various biophysical techniques, including circular dichroism (CD), thioflavin T fluorescence (ThT), dynamic light scattering (DLS), electron microscopy, and terahertz (THz) absorption spectroscopy. The experimental data demonstrated a transformation of {alpha}-helix into {beta}-sheet starting at 26 h. This was followed by the aggregation of insulin, as shown by ThT binding, with a transition midpoint at 41 h, and by the bulk formation of mature aggregates after about 71 h. THz is a quick and non-invasive technique, which has the advantage of allowing the study of the conformational state of biomolecules and tissues. We first applied THz spectroscopy to study the amyloid fibrillation. At the terahertz frequency range of 0.2-2.0 THz, there was an apparent increase in both the absorbance and refractive index in THz spectra. Thus, THz is expected to provide a new way of looking into amyloid fibrillation.

  5. Dynamic terahertz spectroscopy of gas molecules mixed with unwanted aerosol under atmospheric pressure using fibre-based asynchronous-optical-sampling terahertz time-domain spectroscopy.

    PubMed

    Hsieh, Yi-Da; Nakamura, Shota; Abdelsalam, Dahi Ghareab; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Hindle, Francis; Yasui, Takeshi

    2016-06-15

    Terahertz (THz) spectroscopy is a promising method for analysing polar gas molecules mixed with unwanted aerosols due to its ability to obtain spectral fingerprints of rotational transition and immunity to aerosol scattering. In this article, dynamic THz spectroscopy of acetonitrile (CH3CN) gas was performed in the presence of smoke under the atmospheric pressure using a fibre-based, asynchronous-optical-sampling THz time-domain spectrometer. To match THz spectral signatures of gas molecules at atmospheric pressure, the spectral resolution was optimized to 1 GHz with a measurement rate of 1 Hz. The spectral overlapping of closely packed absorption lines significantly boosted the detection limit to 200 ppm when considering all the spectral contributions of the numerous absorption lines from 0.2 THz to 1 THz. Temporal changes of the CH3CN gas concentration were monitored under the smoky condition at the atmospheric pressure during volatilization of CH3CN droplets and the following diffusion of the volatilized CH3CN gas without the influence of scattering or absorption by the smoke. This system will be a powerful tool for real-time monitoring of target gases in practical applications of gas analysis in the atmospheric pressure, such as combustion processes or fire accident.

  6. Dynamic terahertz spectroscopy of gas molecules mixed with unwanted aerosol under atmospheric pressure using fibre-based asynchronous-optical-sampling terahertz time-domain spectroscopy

    PubMed Central

    Hsieh, Yi-Da; Nakamura, Shota; Abdelsalam, Dahi Ghareab; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Hindle, Francis; Yasui, Takeshi

    2016-01-01

    Terahertz (THz) spectroscopy is a promising method for analysing polar gas molecules mixed with unwanted aerosols due to its ability to obtain spectral fingerprints of rotational transition and immunity to aerosol scattering. In this article, dynamic THz spectroscopy of acetonitrile (CH3CN) gas was performed in the presence of smoke under the atmospheric pressure using a fibre-based, asynchronous-optical-sampling THz time-domain spectrometer. To match THz spectral signatures of gas molecules at atmospheric pressure, the spectral resolution was optimized to 1 GHz with a measurement rate of 1 Hz. The spectral overlapping of closely packed absorption lines significantly boosted the detection limit to 200 ppm when considering all the spectral contributions of the numerous absorption lines from 0.2 THz to 1 THz. Temporal changes of the CH3CN gas concentration were monitored under the smoky condition at the atmospheric pressure during volatilization of CH3CN droplets and the following diffusion of the volatilized CH3CN gas without the influence of scattering or absorption by the smoke. This system will be a powerful tool for real-time monitoring of target gases in practical applications of gas analysis in the atmospheric pressure, such as combustion processes or fire accident. PMID:27301319

  7. Dynamic terahertz spectroscopy of gas molecules mixed with unwanted aerosol under atmospheric pressure using fibre-based asynchronous-optical-sampling terahertz time-domain spectroscopy.

    PubMed

    Hsieh, Yi-Da; Nakamura, Shota; Abdelsalam, Dahi Ghareab; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Hindle, Francis; Yasui, Takeshi

    2016-01-01

    Terahertz (THz) spectroscopy is a promising method for analysing polar gas molecules mixed with unwanted aerosols due to its ability to obtain spectral fingerprints of rotational transition and immunity to aerosol scattering. In this article, dynamic THz spectroscopy of acetonitrile (CH3CN) gas was performed in the presence of smoke under the atmospheric pressure using a fibre-based, asynchronous-optical-sampling THz time-domain spectrometer. To match THz spectral signatures of gas molecules at atmospheric pressure, the spectral resolution was optimized to 1 GHz with a measurement rate of 1 Hz. The spectral overlapping of closely packed absorption lines significantly boosted the detection limit to 200 ppm when considering all the spectral contributions of the numerous absorption lines from 0.2 THz to 1 THz. Temporal changes of the CH3CN gas concentration were monitored under the smoky condition at the atmospheric pressure during volatilization of CH3CN droplets and the following diffusion of the volatilized CH3CN gas without the influence of scattering or absorption by the smoke. This system will be a powerful tool for real-time monitoring of target gases in practical applications of gas analysis in the atmospheric pressure, such as combustion processes or fire accident. PMID:27301319

  8. Dynamic terahertz spectroscopy of gas molecules mixed with unwanted aerosol under atmospheric pressure using fibre-based asynchronous-optical-sampling terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Hsieh, Yi-Da; Nakamura, Shota; Abdelsalam, Dahi Ghareab; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Hindle, Francis; Yasui, Takeshi

    2016-06-01

    Terahertz (THz) spectroscopy is a promising method for analysing polar gas molecules mixed with unwanted aerosols due to its ability to obtain spectral fingerprints of rotational transition and immunity to aerosol scattering. In this article, dynamic THz spectroscopy of acetonitrile (CH3CN) gas was performed in the presence of smoke under the atmospheric pressure using a fibre-based, asynchronous-optical-sampling THz time-domain spectrometer. To match THz spectral signatures of gas molecules at atmospheric pressure, the spectral resolution was optimized to 1 GHz with a measurement rate of 1 Hz. The spectral overlapping of closely packed absorption lines significantly boosted the detection limit to 200 ppm when considering all the spectral contributions of the numerous absorption lines from 0.2 THz to 1 THz. Temporal changes of the CH3CN gas concentration were monitored under the smoky condition at the atmospheric pressure during volatilization of CH3CN droplets and the following diffusion of the volatilized CH3CN gas without the influence of scattering or absorption by the smoke. This system will be a powerful tool for real-time monitoring of target gases in practical applications of gas analysis in the atmospheric pressure, such as combustion processes or fire accident.

  9. Terahertz Spectroscopy of the Amidogen Radical, NH2.

    PubMed

    Müller; Klein; Belov; Winnewisser; Morino; Yamada; Saito

    1999-05-01

    The rotational spectrum of the NH2 radical in its &Xtilde;2B1 ground vibronic state was investigated between 614 and 1003 GHz. One hundred fifty-nine newly observed lines (188 hyperfine components) of six rotational transitions with 0 spectroscopy, as well as microwave optical double resonance (MODR) and recent FIR laser sideband data, were also used in the fit. A large set of spectroscopic constants reproduces the input data within experimental uncertainties and permits the precise prediction of low-N, low-Ka transitions of interest for the astrophysical community. In particular, the astrophysically important 111-000 transition of ortho NH2 was observed near 952.57 and 959.50 GHz. Copyright 1999 Academic Press.

  10. Terahertz Spectroscopy of the Amidogen Radical, NH2

    NASA Astrophysics Data System (ADS)

    Müller, Holger S. P.; Klein, Henrik; Belov, Sergei P.; Winnewisser, Gisbert; Morino, Isamu; Yamada, Koichi M. T.; Saito, Shuji

    1999-05-01

    The rotational spectrum of the NH2radical in itsX~2B1ground vibronic state was investigated between 614 and 1003 GHz. One hundred fifty-nine newly observed lines (188 hyperfine components) of six rotational transitions with 0 <=N<= 5 and 0 <=Ka<= 4 were used in the final, global fit of field-free data for the (000) vibrational state. Recent results from Fourier transform far-infrared (FT-FIR), and millimeter- and submillimeter-wave spectroscopy, as well as microwave optical double resonance (MODR) and recent FIR laser sideband data, were also used in the fit. A large set of spectroscopic constants reproduces the input data within experimental uncertainties and permits the precise prediction of low-N, low-Katransitions of interest for the astrophysical community. In particular, the astrophysically important 111-000transition of ortho NH2was observed near 952.57 and 959.50 GHz.

  11. Using Terahertz Spectroscopy to Study Systems with Solar Energy Applications

    NASA Astrophysics Data System (ADS)

    Milot, Rebecca L.; Moore, Gary F.; Martini, Lauren A.; Brudvig, Gary W.; Crabtree, Robert H.; Schmuttenmaer, Charles A.

    2013-06-01

    Biomimetic solar water oxidation systems are being developed as renewable alternatives to fossil fuels. One possible design incorporates thin-film dye-sensitized nanoparticle photoanades to capture and convert visible light to charge carriers and catalysts to facilitate water oxidation. The physical properties of the dye are important due to its position as the light absorber and electron transfer initiator. Given the role that porphyrins play in photosynthesis and their synthetic tunability, they are promising components for these photoanodes. Time-Resolved THz Spectroscopy (TRTS), an optical pump/THz probe technique, is a non-contact electrical probe with proven usefulness for studying electron transfer and conductivity on a sub-picosecond timescale. Using TRTS, the efficiency and dynamics of electron injection from porphyrin dyes into metal oxide surfaces was found to be strongly influenced by the structure and photophysical properties of the dye.

  12. Sub-terahertz resonance spectroscopy of biological macromolecules and cells

    NASA Astrophysics Data System (ADS)

    Globus, Tatiana; Moyer, Aaron; Gelmont, Boris; Khromova, Tatyana; Sizov, Igor; Ferrance, Jerome

    2013-05-01

    Recently we introduced a Sub-THz spectroscopic system for characterizing vibrational resonance features from biological materials. This new, continuous-wave, frequency-domain spectroscopic sensor operates at room temperature between 315 and 480 GHz with spectral resolution of at least 1 GHz and utilizes the source and detector components from Virginia Diode, Inc. In this work we present experimental results and interpretation of spectroscopic signatures from bacterial cells and their biological macromolecule structural components. Transmission and absorption spectra of the bacterial protein thioredoxin, DNA and lyophilized cells of Escherichia coli (E. coli), as well as spores of Bacillus subtillis and B. atrophaeus have been characterized. Experimental results for biomolecules are compared with absorption spectra calculated using molecular dynamics simulation, and confirm the underlying physics for resonance spectroscopy based on interactions between THz radiation and vibrational modes or groups of modes of atomic motions. Such interactions result in multiple intense and narrow specific resonances in transmission/absorption spectra from nano-gram samples with spectral line widths as small as 3 GHz. The results of this study indicate diverse relaxation dynamic mechanisms relevant to sub-THz vibrational spectroscopy, including long-lasting processes. We demonstrate that high sensitivity in resolved specific absorption fingerprints provides conditions for reliable detection, identification and discrimination capability, to the level of strains of the same bacteria, and for monitoring interactions between biomaterials and reagents in near real-time. Additionally, it creates the basis for the development of new types of advanced biological sensors through integrating the developed system with a microfluidic platform for biomaterial samples.

  13. Subwavelength film sensing based on terahertz anti-resonant reflecting hollow waveguides.

    PubMed

    You, Borwen; Lu, Ja-Yu; Liou, Jia-Hong; Yu, Chin-Ping; Chen, Hao-Zai; Liu, Tze-An; Peng, Jin-Long

    2010-08-30

    A simple dielectric hollow-tube has been experimentally demonstrated at terahertz range for bio-molecular layer sensing based on the anti-resonant reflecting wave-guidance mechanism. We experimentally study the dependence of thin-film detection sensitivity on the optical geometrical parameters of tubes, different thicknesses and tube wall refractive indices, and on different resonant frequencies. A polypropylene hollow-tube with optimized sensitivity of 0.003 mm/μm is used to sense a subwavelength-thick (λ/225) carboxypolymethylene molecular overlayer on the tube's inner surface, and the minimum detectable quantity of molecules could be down to 1.22 picomole/mm(2). A double-layered Fabry-Pérot model is proposed for calculating the overlayer thicknesses, which agrees well with the experimental results.

  14. Reflection imaging in the millimeter-wave range using a video-rate terahertz camera

    NASA Astrophysics Data System (ADS)

    Marchese, Linda E.; Terroux, Marc; Doucet, Michel; Blanchard, Nathalie; Pancrati, Ovidiu; Dufour, Denis; Bergeron, Alain

    2016-05-01

    The ability of millimeter waves (1-10 mm, or 30-300 GHz) to penetrate through dense materials, such as leather, wool, wood and gyprock, and to also transmit over long distances due to low atmospheric absorption, makes them ideal for numerous applications, such as body scanning, building inspection and seeing in degraded visual environments. Current drawbacks of millimeter wave imaging systems are they use single detector or linear arrays that require scanning or the two dimensional arrays are bulky, often consisting of rather large antenna-couple focal plane arrays (FPAs). Previous work from INO has demonstrated the capability of its compact lightweight camera, based on a 384 x 288 microbolometer pixel FPA with custom optics for active video-rate imaging at wavelengths of 118 μm (2.54 THz), 432 μm (0.69 THz), 663 μm (0.45 THz), and 750 μm (0.4 THz). Most of the work focused on transmission imaging, as a first step, but some preliminary demonstrations of reflection imaging at these were also reported. In addition, previous work also showed that the broadband FPA remains sensitive to wavelengths at least up to 3.2 mm (94 GHz). The work presented here demonstrates the ability of the INO terahertz camera for reflection imaging at millimeter wavelengths. Snapshots taken at video rates of objects show the excellent quality of the images. In addition, a description of the imaging system that includes the terahertz camera and different millimeter sources is provided.

  15. Terahertz time domain spectroscopy of hydrothermally synthesized boehmite and ammonium dawsonite nanostructures

    NASA Astrophysics Data System (ADS)

    Mehboob, Shoaib; Mehmood, Mazhar; Ahmed, Mushtaq; Ahmad, Jamil; Tanvir, Muhammad Tauseef; Ahmad, Izhar

    2016-09-01

    The frequency dependent optical and dielectric properties of boehmite (AlOOH) and ammonium aluminum carbonate hydroxide (AACH) nanostructures, prepared at different temperatures via hydrothermal synthesis, were studied by using terahertz time domain spectroscopy (THz-TDS). The complex refractive indices, absorption coefficients and complex dielectric constants were determined and compared for different synthesis temperatures. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were also performed to confirm the formation of boehmite and AACH. Scanning electron microscopy (SEM) was performed to study the morphology of nanostructures. The study reveals the formation of AACH at higher temperatures and decrease in refractive index with increasing synthesis temperature. The higher absorption coefficient and lower refractive index and dielectric constant were observed for AACH than for boehmite.

  16. Non-destructive inspections of illicit drugs in envelope using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Ning; Shen, Jingling; Lu, Meihong; Jia, Yan; Sun, Jinhai; Liang, Laishun; Shi, Yanning; Xu, Xiaoyu; Zhang, Cunlin

    2006-09-01

    The absorption spectra of two illicit drugs, methylenedioxyamphetarnine (MDA) and methamphetamine (MA), within and without two conventional envelopes are studied using terahertz time-domain spectroscopy technique. The characteristic absorption spectra of MDA and MA are obtained in the range of 0.2 THz to 2.5 THz. MDA has an obvious absorption peak at 1.41 THz while MA has obvious absorption peaks at 1.23 THz, 1.67 THz, 1.84 THz and 2.43 THz. We find that the absorption peaks of MDA and MA within the envelopes are almost the same as those without the envelopes respectively although the two envelopes have some different absorption in THz waveband. This result indicates that the type of illicit drugs in envelopes can be determined by identifying their characteristic absorption peaks, and THz time-domain spectroscopy is one of the most powerful candidates for illicit drugs inspection.

  17. Near-Field Spectroscopy and Imaging of Subwavelength Plasmonic Terahertz Resonators

    DOE PAGESBeta

    Mitrofanov, Oleg; Khromova, Irina; Siday, Thomas; Thompson, Robert J.; Ponomarev, Andrey N.; Brener, Igal; Reno, John L.

    2016-04-22

    We describe the temporal evolution of the terahertz (THz) field leading to the excitation of plasmonic resonances in carbon microfibers. The field evolution is mapped in space and time for the 3/2 wavelength resonance using a subwavelength aperture THz near-field probe with an embedded THz photoconductive detector. The excitation of surface waves at the fiber tips leads to the formation of a standing wave along the fiber. Local THz time-domain spectroscopy at one of the standing wave crests shows a clear third-order resonance peak at 1.65 THz, well described by the Lorentz model. Lastly, this application of the subwavelength aperturemore » THz near-field microscopy for mode mapping and local spectroscopy demonstrates the potential of near-field methods for studies of subwavelength plasmonic THz resonators.« less

  18. Terahertz spectroscopy for the study of paraffin-embedded gastric cancer samples

    NASA Astrophysics Data System (ADS)

    Wahaia, Faustino; Kasalynas, Irmantas; Seliuta, Dalius; Molis, Gediminas; Urbanowicz, Andrzej; Carvalho Silva, Catia D.; Carneiro, Fatima; Valusis, Gintaras; Granja, Pedro L.

    2015-01-01

    Terahertz (THz) spectroscopy constitute promising technique for biomedical applications as a complementary and powerful tool for diseases screening specially for early cancer diagnostic. The THz radiation is not harmful to biological tissues. As increased blood supply in cancer-affected tissues and consequent local increase in tissue water content makes THz technology a potentially attractive. In the present work, samples of healthy and adenocarcinoma-affected gastric tissue were analyzed using transmission time-domain THz spectroscopy (THz-TDS). The work shows the capability of the technique to distinguish between normal and cancerous regions in dried and paraffin-embedded samples. Plots of absorption coefficient α and refractive index n of normal and cancer affected tissues, are presented and the conditions for discrimination between normal and affected tissues are discussed.

  19. Light distribution modulated diffuse reflectance spectroscopy.

    PubMed

    Huang, Pin-Yuan; Chien, Chun-Yu; Sheu, Chia-Rong; Chen, Yu-Wen; Tseng, Sheng-Hao

    2016-06-01

    Typically, a diffuse reflectance spectroscopy (DRS) system employing a continuous wave light source would need to acquire diffuse reflectances measured at multiple source-detector separations for determining the absorption and reduced scattering coefficients of turbid samples. This results in a multi-fiber probe structure and an indefinite probing depth. Here we present a novel DRS method that can utilize a few diffuse reflectances measured at one source-detector separation for recovering the optical properties of samples. The core of innovation is a liquid crystal (LC) cell whose scattering property can be modulated by the bias voltage. By placing the LC cell between the light source and the sample, the spatial distribution of light in the sample can be varied as the scattering property of the LC cell modulated by the bias voltage, and this would induce intensity variation of the collected diffuse reflectance. From a series of Monte Carlo simulations and phantom measurements, we found that this new light distribution modulated DRS (LDM DRS) system was capable of accurately recover the absorption and scattering coefficients of turbid samples and its probing depth only varied by less than 3% over the full bias voltage variation range. Our results suggest that this LDM DRS platform could be developed to various low-cost, efficient, and compact systems for in-vivo superficial tissue investigation. PMID:27375931

  20. Light distribution modulated diffuse reflectance spectroscopy

    PubMed Central

    Huang, Pin-Yuan; Chien, Chun-Yu; Sheu, Chia-Rong; Chen, Yu-Wen; Tseng, Sheng-Hao

    2016-01-01

    Typically, a diffuse reflectance spectroscopy (DRS) system employing a continuous wave light source would need to acquire diffuse reflectances measured at multiple source-detector separations for determining the absorption and reduced scattering coefficients of turbid samples. This results in a multi-fiber probe structure and an indefinite probing depth. Here we present a novel DRS method that can utilize a few diffuse reflectances measured at one source-detector separation for recovering the optical properties of samples. The core of innovation is a liquid crystal (LC) cell whose scattering property can be modulated by the bias voltage. By placing the LC cell between the light source and the sample, the spatial distribution of light in the sample can be varied as the scattering property of the LC cell modulated by the bias voltage, and this would induce intensity variation of the collected diffuse reflectance. From a series of Monte Carlo simulations and phantom measurements, we found that this new light distribution modulated DRS (LDM DRS) system was capable of accurately recover the absorption and scattering coefficients of turbid samples and its probing depth only varied by less than 3% over the full bias voltage variation range. Our results suggest that this LDM DRS platform could be developed to various low-cost, efficient, and compact systems for in-vivo superficial tissue investigation. PMID:27375931

  1. Tunnelling current-voltage characteristics of Angstrom gaps measured with terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Kim, Joon-Yeon; Kang, Bong Joo; Bahk, Young-Mi; Kim, Yong Seung; Park, Joohyun; Kim, Won Tae; Rhie, Jiyeah; Han, Sanghoon; Jeon, Hyeongtag; Park, Cheol-Hwan; Rotermund, Fabian; Kim, Dai-Sik

    2016-06-01

    Quantum tunnelling becomes inevitable as gap dimensions in metal structures approach the atomic length scale, and light passing through these gaps can be used to examine the quantum processes at optical frequencies. Here, we report on the measurement of the tunnelling current through a 3-Å-wide metal-graphene-metal gap using terahertz time-domain spectroscopy. By analysing the waveforms of the incident and transmitted terahertz pulses, we obtain the tunnelling resistivity and the time evolution of the induced current and electric fields in the gap and show that the ratio of the applied voltage to the tunnelling current is constant, i.e., the gap shows ohmic behaviour for the strength of the incident electric field up to 30 kV/cm. We further show that our method can be extended and applied to different types of nanogap tunnel junctions using suitable equivalent RLC circuits for the corresponding structures by taking an array of ring-shaped nanoslots as an example.

  2. Tunnelling current-voltage characteristics of Angstrom gaps measured with terahertz time-domain spectroscopy.

    PubMed

    Kim, Joon-Yeon; Kang, Bong Joo; Bahk, Young-Mi; Kim, Yong Seung; Park, Joohyun; Kim, Won Tae; Rhie, Jiyeah; Han, Sanghoon; Jeon, Hyeongtag; Park, Cheol-Hwan; Rotermund, Fabian; Kim, Dai-Sik

    2016-01-01

    Quantum tunnelling becomes inevitable as gap dimensions in metal structures approach the atomic length scale, and light passing through these gaps can be used to examine the quantum processes at optical frequencies. Here, we report on the measurement of the tunnelling current through a 3-Å-wide metal-graphene-metal gap using terahertz time-domain spectroscopy. By analysing the waveforms of the incident and transmitted terahertz pulses, we obtain the tunnelling resistivity and the time evolution of the induced current and electric fields in the gap and show that the ratio of the applied voltage to the tunnelling current is constant, i.e., the gap shows ohmic behaviour for the strength of the incident electric field up to 30 kV/cm. We further show that our method can be extended and applied to different types of nanogap tunnel junctions using suitable equivalent RLC circuits for the corresponding structures by taking an array of ring-shaped nanoslots as an example. PMID:27357346

  3. Tunnelling current-voltage characteristics of Angstrom gaps measured with terahertz time-domain spectroscopy

    PubMed Central

    Kim, Joon-Yeon; Kang, Bong Joo; Bahk, Young-Mi; Kim, Yong Seung; Park, Joohyun; Kim, Won Tae; Rhie, Jiyeah; Han, Sanghoon; Jeon, Hyeongtag; Park, Cheol-Hwan; Rotermund, Fabian; Kim, Dai-Sik

    2016-01-01

    Quantum tunnelling becomes inevitable as gap dimensions in metal structures approach the atomic length scale, and light passing through these gaps can be used to examine the quantum processes at optical frequencies. Here, we report on the measurement of the tunnelling current through a 3-Å-wide metal-graphene-metal gap using terahertz time-domain spectroscopy. By analysing the waveforms of the incident and transmitted terahertz pulses, we obtain the tunnelling resistivity and the time evolution of the induced current and electric fields in the gap and show that the ratio of the applied voltage to the tunnelling current is constant, i.e., the gap shows ohmic behaviour for the strength of the incident electric field up to 30 kV/cm. We further show that our method can be extended and applied to different types of nanogap tunnel junctions using suitable equivalent RLC circuits for the corresponding structures by taking an array of ring-shaped nanoslots as an example. PMID:27357346

  4. Characterisation of historic plastics using terahertz time-domain spectroscopy and pulsed imaging.

    PubMed

    Pastorelli, Gianluca; Trafela, Tanja; Taday, Phillip F; Portieri, Alessia; Lowe, David; Fukunaga, Kaori; Strlič, Matija

    2012-05-01

    Terahertz (THz) time-domain spectroscopy and 3D THz pulsed imaging have been explored with regard to polymer materials, both commodity and historic polymers. A systematic spectroscopic study of a wide range of different polymer materials showed significant differences in their spectra. Polyolefins and polystyrenes generally exhibit lower absorption than other examined polymers, various cellulose derivates, poly(vinyl chloride), poly(methyl methacrylate), polyamide, hard rubber and phenol formaldehyde resin, the last of these exhibiting the most intense absorption over the entire range, 0.15-4.2 THz. It was also examined how the presence of plasticisers in poly(vinyl chloride), the presence of fillers in polypropylene, and the degree of branching in polyethylene and polystyrene affect the spectra; inorganic fillers in polypropylene affected the absorption most. With 3D THz pulsed imaging, features in polymer objects were explored, appearing either as integral parts of the material (coatings and pores in foams) or as a consequence of physical deterioration (cracks, delamination). All of these features of various complexities can be successfully imaged in 3D. Terahertz technology is thus shown to have significant potential for both chemical and structural characterisation of polymers, which will be of interest to heritage science, but also to the polymer industry and development of analytical technologies in general.

  5. Discrimination of Transgenic Rice containing the Cry1Ab Protein using Terahertz Spectroscopy and Chemometrics

    NASA Astrophysics Data System (ADS)

    Xu, Wendao; Xie, Lijuan; Ye, Zunzhong; Gao, Weilu; Yao, Yang; Chen, Min; Qin, Jianyuan; Ying, Yibin

    2015-07-01

    Spectroscopic techniques combined with chemometrics methods have proven to be effective tools for the discrimination of objects with similar properties. In this work, terahertz time-domain spectroscopy (THz-TDS) combined with discriminate analysis (DA) and principal component analysis (PCA) with derivative pretreatments was performed to differentiate transgenic rice (Hua Hui 1, containing the Cry1Ab protein) from its parent (Ming Hui 63). Both rice samples and the Cry1Ab protein were ground and pressed into pellets for terahertz (THz) measurements. The resulting time-domain spectra were transformed into frequency-domain spectra, and then, the transmittances of the rice and Cry1Ab protein were calculated. By applying the first derivative of the THz spectra in conjunction with the DA model, the discrimination of transgenic from non-transgenic rice was possible with accuracies up to 89.4% and 85.0% for the calibration set and validation set, respectively. The results indicated that THz spectroscopic techniques and chemometrics methods could be new feasible ways to differentiate transgenic rice.

  6. Conductivity of ZnO nanowires, nanoparticles, and thin films using time-resolved terahertz spectroscopy.

    PubMed

    Baxter, Jason B; Schmuttenmaer, Charles A

    2006-12-21

    The terahertz absorption coefficient, index of refraction, and conductivity of nanostructured ZnO have been determined using time-resolved terahertz spectroscopy, a noncontact optical probe. ZnO properties were measured directly for thin films and were extracted from measurements of nanowire arrays and mesoporous nanoparticle films by applying Bruggeman effective medium theory to the composite samples. Annealing significantly reduces the intrinsic carrier concentration in the ZnO films and nanowires, which were grown by chemical bath deposition. The complex-valued, frequency-dependent photoconductivities for all morphologies were found to be similar at short pump-probe delay times. Fits using the Drude-Smith model show that films have the highest mobility, followed by nanowires and then nanoparticles, and that annealing the ZnO increases its mobility. Time constants for decay of photoinjected electron density in films are twice as long as those in nanowires and more than 5 times those for nanoparticles due to increased electron interaction with interfaces and grain boundaries in the smaller-grained materials. Implications for electron transport in dye-sensitized solar cells are discussed.

  7. Spectroscopy study of ephedrine hydrochloride and papaverine hydrochloride in terahertz range

    NASA Astrophysics Data System (ADS)

    Deng, Fusheng; Shen, Jingling; Wang, Guangqin; Liang, Meiyan

    2008-12-01

    The terahertz(THz) fingerprint spectra of Ephedrine Hydrochloride and Papaverine Hydrochloride have been measured using THz time-domain Spectroscopy (THz-TDS) system in the region of 0.2~2.6 THz. To explain the spectra, both gas-phase simulation methods and solid-state simulation methods were performed in the efforts to extract pictures of the molecular interior vibrational modes. By comparing the results of various gas-phase simulation methods, It was found that using the semi-empirical theory is more applicable than the density functional theory (DFT) for some chemical compounds. In the solid-state calculations, solid-state density functional theory (DFT) was employed to obtain the vibration frequencies and Difference-Dipole Method (DDM) was used to calculate the corresponding infrared (IR) intensity. In the process of calculating the IR intensity of Papaverine Hydrochloride in terahertz range, we found that the results by Hirshfeld partitioning method agree better with the experiments than the ones derived from Mulliken atomic charges. Moreover, the accuracy of simulation results depends on the basis sets and grid size being chosen.

  8. Discrimination of Transgenic Rice containing the Cry1Ab Protein using Terahertz Spectroscopy and Chemometrics

    PubMed Central

    Xu, Wendao; Xie, Lijuan; Ye, Zunzhong; Gao, Weilu; Yao, Yang; Chen, Min; Qin, Jianyuan; Ying, Yibin

    2015-01-01

    Spectroscopic techniques combined with chemometrics methods have proven to be effective tools for the discrimination of objects with similar properties. In this work, terahertz time-domain spectroscopy (THz-TDS) combined with discriminate analysis (DA) and principal component analysis (PCA) with derivative pretreatments was performed to differentiate transgenic rice (Hua Hui 1, containing the Cry1Ab protein) from its parent (Ming Hui 63). Both rice samples and the Cry1Ab protein were ground and pressed into pellets for terahertz (THz) measurements. The resulting time-domain spectra were transformed into frequency-domain spectra, and then, the transmittances of the rice and Cry1Ab protein were calculated. By applying the first derivative of the THz spectra in conjunction with the DA model, the discrimination of transgenic from non-transgenic rice was possible with accuracies up to 89.4% and 85.0% for the calibration set and validation set, respectively. The results indicated that THz spectroscopic techniques and chemometrics methods could be new feasible ways to differentiate transgenic rice. PMID:26154950

  9. Multiple regimes of carrier cooling in photoexcited graphene probed by time-resolved terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Frenzel, A. J.; Gabor, N. M.; Herring, P. K.; Fang, W.; Kong, J.; Jarillo-Herrero, P.; Gedik, N.

    2013-03-01

    Energy relaxation and cooling of photoexcited charge carriers in graphene has recently attracted significant attention due to possible hot carrier effects, large quantum efficiencies, and photovoltaic applications. However, the details of these processes remain poorly understood, with many conflicting interpretations reported. Here we use time-resolved terahertz spectroscopy to explore multiple relaxation and cooling regimes in graphene in order to elucidate the fundamental physical processes which occur upon photoexcitation of charge carriers. We observe a novel negative terahertz photoconductivity that results from the unique linear dispersion and allows us to measure the electron temperature with ultrafast time resolution. Additionally, we present measurements of the relaxation dynamics over a wide range of excitation fluence. By varying the pump photon energy, we demonstrate that cooling dynamics of photoexcited carriers depend on the amount of energy deposited in the graphene system by the pump pulse, not the number of absorbed photons. The data suggest that fundamentally different regimes are encountered for different excitation fluences. These results may provide a unifying framework for reconciling various measurements of energy relaxation and cooling in graphene.

  10. Direct measurement of molecular mobility and crystallisation of amorphous pharmaceuticals using terahertz spectroscopy.

    PubMed

    Sibik, Juraj; Zeitler, J Axel

    2016-05-01

    Despite much effort in the area, no comprehensive understanding of the formation and behaviour of amorphous solids has yet been achieved. This severely limits the industrial application of such materials, including drug delivery where, in principle, amorphous solids have demonstrated their great usefulness in increasing the bioavailability of poorly aqueous soluble active pharmaceutical ingredients. Terahertz time-domain spectroscopy is a relatively novel analytical technique that can be used to measure the fast molecular dynamics of molecules with high accuracy in a non-contact and non-destructive fashion. Over the past decade a number of applications for the characterisation of amorphous drug molecules and formulations have been developed and it has been demonstrated how this technique can be used to determine the onset and strength in molecular mobility that underpins the crystallisation of amorphous drugs. In this review we provide an overview of the history, fundamentals and future perspective of pharmaceutical applications related to the terahertz dynamics of amorphous systems. PMID:26772139

  11. Parallel plate waveguide time domain spectroscopy to study terahertz conductivity of utltrathin materials

    NASA Astrophysics Data System (ADS)

    Razanoelina, Manjakavahoaka; Bagsican, Filchito R.; Kawayama, Iwao; Zhang, Xiang; Ma, Lulu; Murakami, Hironaru; Vajtai, Robert; Ajayan, Pulickel M.; Kono, Junichiro; Mittleman, Daniel M.; Tonouchi, Masayoshi

    2016-04-01

    The newly discovered atomically thin and layered materials which host electronic system that respond to longwavelength light in extraordinary manner can lead to a major breakthrough in the field of terahertz (THz) optics and photonics. However, their low conductivities due to either low densities or low mobility make it challenging to characterize their basic THz properties with the standard spectroscopic method. Here, we develop a THz spectroscopic technique based on parallel plate waveguide (PPWG) to overcome the limitations of the conventional THz time domain spectroscopy (TDS) technique. The present method is particularly suitable to ultrathin conductive materials with low carrier density. We report in details the derivation of the dispersion equations of the terahertz wave propagation in a PPWG loaded by a thin conductive materials with zero-thickness. These dispersion equations for transverse magnetic (TM) and transverse electric (TE) waveguide modes are the core of the optical parameters extraction algorithm in the THz-PPWG-TDS analysis. We demonstrate the effectiveness of the waveguide approach by characterizing low conductive CVD graphene. The high sensitivity of THz-PPWG-TDS technique enables us to study the carrier dynamics in graphene with Drude and Drude-Smith model.

  12. Label-free detection and characterization of the binding of hemagglutinin protein and broadly neutralizing monoclonal antibodies using terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Sun, Yiwen; Zhong, Junlan; Zhang, Cunlin; Zuo, Jian; Pickwell-MacPherson, Emma

    2015-03-01

    Hemagglutinin (HA) is the main surface glycoprotein of the influenza A virus. The H9N2 subtype influenza A virus is recognized as the most possible pandemic strain as it has crossed the species barrier, infecting swine and humans. We use terahertz spectroscopy to study the hydration shell formation around H9 subtype influenza A virus's HA protein (H9 HA) as well as the detection of antigen binding of H9 HA with the broadly neutralizing monoclonal antibody. We observe a remarkable concentration dependent nonlinear response of the H9 HA, which reveals the formation process of the hydration shell around H9 HA molecules. Furthermore, we show that terahertz dielectric properties of the H9 HA are strongly affected by the presence of the monoclonal antibody F10 and that the terahertz dielectric loss tangent can be used to detect the antibody binding at lower concentrations than the standard ELISA test.

  13. Distinguishing of different kinds of gunpowder using various methods based on terahertz radiation

    NASA Astrophysics Data System (ADS)

    Gavenda, Tomáš; Křesálek, Vojtěch

    2014-10-01

    This article provides information about using terahertz radiation based methods such as time-domain spectroscopy, ATR spectroscopy and terahertz reflection imaging for distinguishing of different kinds of gunpowder. The findings in this article prove that gunpowder does not have any sharp peaks in terahertz region of electromagnetic spectrum up to 2.5 THz, but also prove that distinguishing of different kinds of gunpowder is possible using different methods based on terahertz radiation. All presented results are connected to absorbance of gunpowder and other measured materials, because comparison of absorbance analysis is essential for distinguishing of gunpowder samples.

  14. Optical Reflection Spectroscopy of GEO Objects

    NASA Technical Reports Server (NTRS)

    Seitzer, Patrick; Cardona, Tammaso; Lederer, Susan M.; Cowardin, Heather; Abercromby, Kira J.; Barker, Edwin S.; Bedard, Donald

    2013-01-01

    We report on optical reflection spectroscopy of geosynchronous (GEO) objects in the US Space Surveillance Network (SSN) catalog. These observations were obtained using imaging spectrographs on the 6.5-m Magellan telescopes at the Las Campanas Observatory in Chile. Our goal is to determine the composition of these objects by comparing these spectral observations with ground-based laboratory measurements of spacecraft materials. The observations are all low resolution (1 nm after smoothing) obtained through a 5 arcsecond wide slit and using a grism as the dispersing element. The spectral range covered was from 450 nm to 800 nm. All spectra were flux calibrated using observations of standard stars with the exact same instrumental setup. An effort was made to obtain all observations within a limited range of topocentric phase angle, although the solar incident angle is unknown due to the lack of any knowledge of the attitude of the observed surface at the time of observation.

  15. A review of the electrical properties of semiconductor nanowires: insights gained from terahertz conductivity spectroscopy

    NASA Astrophysics Data System (ADS)

    Joyce, Hannah J.; Boland, Jessica L.; Davies, Christopher L.; Baig, Sarwat A.; Johnston, Michael B.

    2016-10-01

    Accurately measuring and controlling the electrical properties of semiconductor nanowires is of paramount importance in the development of novel nanowire-based devices. In light of this, terahertz (THz) conductivity spectroscopy has emerged as an ideal non-contact technique for probing nanowire electrical conductivity and is showing tremendous value in the targeted development of nanowire devices. THz spectroscopic measurements of nanowires enable charge carrier lifetimes, mobilities, dopant concentrations and surface recombination velocities to be measured with high accuracy and high throughput in a contact-free fashion. This review spans seminal and recent studies of the electronic properties of nanowires using THz spectroscopy. A didactic description of THz time-domain spectroscopy, optical pump-THz probe spectroscopy, and their application to nanowires is included. We review a variety of technologically important nanowire materials, including GaAs, InAs, InP, GaN and InN nanowires, Si and Ge nanowires, ZnO nanowires, nanowire heterostructures, doped nanowires and modulation-doped nanowires. Finally, we discuss how THz measurements are guiding the development of nanowire-based devices, with the example of single-nanowire photoconductive THz receivers.

  16. Intrinsic carrier multiplication efficiency in bulk Si crystals evaluated by optical-pump/terahertz-probe spectroscopy

    SciTech Connect

    Yamashita, G.; Nagai, M. E-mail: ashida@mp.es.osaka-u.ac.jp; Ashida, M. E-mail: ashida@mp.es.osaka-u.ac.jp; Matsubara, E.; Kanemitsu, Y.

    2014-12-08

    We estimated the carrier multiplication efficiency in the most common solar-cell material, Si, by using optical-pump/terahertz-probe spectroscopy. Through close analysis of time-resolved data, we extracted the exact number of photoexcited carriers from the sheet carrier density 10 ps after photoexcitation, excluding the influences of spatial diffusion and surface recombination in the time domain. For incident photon energies greater than 4.0 eV, we observed enhanced internal quantum efficiency due to carrier multiplication. The evaluated value of internal quantum efficiency agrees well with the results of photocurrent measurements. This optical method allows us to estimate the carrier multiplication and surface recombination of carriers quantitatively, which are crucial for the design of the solar cells.

  17. The Vibrational Spectra of Bactericide molecules: Terahertz Spectroscopy and Density Functional Theory Calculations

    NASA Astrophysics Data System (ADS)

    Wang, Xiaowei; Wang, Qiang

    2011-02-01

    In the room temperature and nitrogen conditions, we presented well-resolved absorption spectra and indexes of refraction of bactericide molecules in the far infrared radiation (FIR) spectral region recorded by terahertz time-domain spectroscopy (THz-TDS). As illustrative examples we discussed the absorption spectra of captan and folpet in THz region. The absorption coefficient and index of refraction of them were obtained. Meanwhile, density functional theory (DFT) with software package Gaussian 03 using B3LYP theory was employed for optimization and vibration analysis. With the help of Gaussian View 3.09, the distinct absorption peaks of those molecules were assigned with reliable accuracy. They were caused by intermolecular hydrogen-bonding, molecular torsion or vibration modes, absorption of water molecules, etc. As the absorption spectra are highly sensitive to the overall structure and configuration of the molecules, the THz-TDS procedure can provide a direct fingerprint of the molecular structure or conformational state of a compound.

  18. Measuring the Elasticity of Poly-l-Proline Helices with Terahertz Spectroscopy.

    PubMed

    Ruggiero, Michael T; Sibik, Juraj; Orlando, Roberto; Zeitler, J Axel; Korter, Timothy M

    2016-06-01

    The rigidity of poly-l-proline is an important contributor to the stability of many protein secondary structures, where it has been shown to strongly influence bulk flexibility. The experimental Young's moduli of two known poly-l-proline helical forms, right-handed all-cis (Form I) and left-handed all-trans (Form II), were determined in the crystalline state by using an approach that combines terahertz time-domain spectroscopy, X-ray diffraction, and solid-state density functional theory. Contrary to expectations, the helices were found to be considerably less rigid than many other natural and synthetic polymers, as well as differing greatly from each other, with Young's moduli of 4.9 and 9.6 GPa for Forms I and II, respectively. PMID:27121300

  19. Hyper sausage neuron: Recognition of transgenic sugar-beet based on terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Jianjun; Li, Zhi; Hu, Fangrong; Chen, Tao; Du, Yong; Xin, Haitao

    2015-01-01

    This paper presents a novel approach for identification of terahertz (THz) spectral of genetically modified organisms (GMOs) based on Hyper Sausage Neuron (HSN), and THz transmittance spectra of some typical transgenic sugar-beet samples are investigated to demonstrate its feasibility. Principal component analysis (PCA) is applied to extract features of the spectrum data, and instead of the original spectrum data, the feature signals are fed into the HSN pattern recognition, a new multiple weights neural network (MWNN). The experimental result shows that the HSN model not only can correctly classify different types of transgenic sugar-beets, but also can reject identity non similar samples in the same type. The proposed approach provides a new effective method for detection and identification of GMOs by using THz spectroscopy.

  20. Identification of Transgenic Organisms Based on Terahertz Spectroscopy and Hyper Sausage Neuron

    NASA Astrophysics Data System (ADS)

    Liu, J.; Li, Zh.; Hu, F.; Chen, T.; Du, Y.; Xin, H.

    2015-03-01

    This paper presents a novel approach for identifi cation of terahertz (THz) spectra of genetically modifi ed organisms (GMOs) based on hyper sausage neuron (HSN), and THz transmittance spectra of some typical transgenic sugarbeet samples are investigated to demonstrate its feasibility. Principal component analysis (PCA) is applied to extract features of the spectrum data, and instead of the original spectrum data, the feature signals are fed into the HSN pattern recognition, a new multiple weights neural network (MWNN). The experimental result shows that the HSN model not only can correctly classify different types of transgenic sugar-beets, but also can reject nonsimilar samples of the same type. The proposed approach provides a new effective method for detection and identification of genetically modified organisms by using THz spectroscopy.

  1. A Modified 8 f Geometry with Reduced Optical Aberrations for Improved Time Domain Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Laurita, N. J.; Cheng, Bing; Barkhouser, R.; Neumann, V. A.; Armitage, N. P.

    2016-09-01

    We present a modified 8 f geometry for time domain terahertz (THz) spectroscopy (TDTS) experiments. We show, through simulations and data, that a simple rearranging of the off-axis parabolic mirrors, which are typically used to focus and direct THz radiation in TDTS experiments, results in a nearly 40 % reduction in the THz focal spot diameter. This effect stems from significant reduction of the principle optical aberrations which are enhanced in the conventional 8 f geometry but partially compensated in the modified 8 f experimental setup. We compare data from our home-built TDTS spectrometer in the modified 8 f geometry to that of previous iterations that were designed in the conventional 8 f geometry to demonstrate the effect.

  2. Rapid determination of saponification value and polymer content of vegetable and fish oils by terahertz spectroscopy.

    PubMed

    Jiang, Feng Ling; Ikeda, Ikuo; Ogawa, Yuichi; Endo, Yasushi

    2012-01-01

    A rapid method for determining the saponification value (SV) and polymer content of vegetable and fish oils using the terahertz (THz) spectroscopy was developed. When the THz absorption spectra for vegetable and fish oils were measured in the range of 20 to 400 cm⁻¹, two peaks were seen at 77 and 328 cm⁻¹. The level of absorbance at 77 cm⁻¹ correlated well with the SV. When the THz absorption spectra of thermally treated high-oleic safflower oils were measured, the absorbance increased with heating time. The polymer content in thermally treated oil correlated with the absorbance at 77 cm⁻¹. These results demonstrate that the THz spectrometry is a suitable non-destructive technique for the rapid determination of the SV and polymer content of vegetable and fish oils.

  3. Density Detection of Aligned Nanowire Arrays Using Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Xiang, Wenfeng; Wang, Xin; Liu, Yuan; Zhang, JiaQi; Zhao, Kun

    2016-07-01

    A rapid technique is necessary to quantitatively detect the density of nanowire (NW) and nanotube arrays in one-dimensional devices which have been identified as useful building blocks for nanoelectronics, optoelectronics, biomedical devices, etc. Terahertz (THz) time-domain spectroscopy was employed in this research to detect the density of aligned Ni NW arrays. The transmitted amplitude of THz peaks and optical thickness of NW arrays was found to be the effective parameters to analyze the density change of NW arrays. Owing to the low multiple scattering and high order of Ni NW arrays, a linear relationship was observed for the transmitted amplitude and optical thickness regarding NW density, respectively. Therefore, THz technique may be used as a promising tool to characterize the density of one-dimensional structures in the large-scale integrated nanodevice fabrication.

  4. Far-infrared characteristics of ZnS nanoparticles measured by terahertz time-domain spectroscopy.

    PubMed

    Han, Jiaguang; Zhang, Weili; Chen, Wei; Thamizhmani, L; Azad, Abul K; Zhu, Zhiyuan

    2006-02-01

    The optical and dielectric properties of ZnS nanoparticles are studied by use of terahertz time-domain spectroscopy (THz-TDS) over the frequency range from 0.3 to 3.0 THz. The effective medium approach combined with the pseudo-harmonic model of the dielectric response, where nanoparticles are embedded in the host medium, provides a good fit on the experimental results. The extrapolation of the measured data indicates that the absorption is dominated by the transverse optical mode localized at 11.6+/-0.2 THz. Meanwhile, the low-frequency phonon resonance of ZnS nanoparticles is compared with the single-crystal ZnS. The THz-TDS clearly reveals the remarkable distinction in the low-frequency phonon resonances between ZnS nanoparticles and single-crystal ZnS. The results demonstrate that the acoustic phonons become confined in small-size nanoparticles.

  5. Density Detection of Aligned Nanowire Arrays Using Terahertz Time-Domain Spectroscopy.

    PubMed

    Xiang, Wenfeng; Wang, Xin; Liu, Yuan; Zhang, JiaQi; Zhao, Kun

    2016-12-01

    A rapid technique is necessary to quantitatively detect the density of nanowire (NW) and nanotube arrays in one-dimensional devices which have been identified as useful building blocks for nanoelectronics, optoelectronics, biomedical devices, etc. Terahertz (THz) time-domain spectroscopy was employed in this research to detect the density of aligned Ni NW arrays. The transmitted amplitude of THz peaks and optical thickness of NW arrays was found to be the effective parameters to analyze the density change of NW arrays. Owing to the low multiple scattering and high order of Ni NW arrays, a linear relationship was observed for the transmitted amplitude and optical thickness regarding NW density, respectively. Therefore, THz technique may be used as a promising tool to characterize the density of one-dimensional structures in the large-scale integrated nanodevice fabrication.

  6. Terahertz magneto-optical spectroscopy of a two-dimensional hole gas

    SciTech Connect

    Kamaraju, N. Taylor, A. J.; Prasankumar, R. P.; Pan, W.; Reno, J.; Ekenberg, U.; Gvozdić, D. M.; Boubanga-Tombet, S.; Upadhya, P. C.

    2015-01-19

    Two-dimensional hole gases (2DHGs) have attracted recent attention for their unique quantum physics and potential applications in areas including spintronics and quantum computing. However, their properties remain relatively unexplored, motivating the use of different techniques to study them. We used terahertz magneto-optical spectroscopy to investigate the cyclotron resonance frequency in a high mobility 2DHG, revealing a nonlinear dependence on the applied magnetic field. This is shown to be due to the complex non-parabolic valence band structure of the 2DHG, as verified by multiband Landau level calculations. We also find that impurity scattering dominates cyclotron resonance decay in the 2DHG, in contrast with the dominance of superradiant damping in two-dimensional electron gases. Our results shed light on the properties of 2DHGs, motivating further studies of these unique 2D nanosystems.

  7. Terahertz magneto-optical spectroscopy of a two-dimensional hole gas

    SciTech Connect

    Kamaraju, N.; Pan, W.; Ekenberg, U.; Gvozdić, D. M.; Boubanga-Tombet, S.; Upadhya, P. C.; Reno, J.; Taylor, A. J.; Prasankumar, R. P.

    2015-01-21

    Two-dimensional hole gases (2DHGs) have attracted recent attention for their unique quantum physics and potential applications in areas including spintronics and quantum computing. However, their properties remain relatively unexplored, motivating the use of different techniques to study them. We then used terahertz magneto-optical spectroscopy to investigate the cyclotron resonance frequency in a high mobility 2DHG, revealing a nonlinear dependence on the applied magnetic field. This is shown to be due to the complex non-parabolic valence band structure of the 2DHG, as verified by multiband Landau level calculations. We also found that impurity scattering dominates cyclotron resonance decay in the 2DHG, in contrast with the dominance of superradiant damping in two-dimensional electron gases. Our results shed light on the properties of 2DHGs, motivating further studies of these unique 2D nanosystems.

  8. Terahertz magneto-optical spectroscopy of a two-dimensional hole gas

    DOE PAGESBeta

    Kamaraju, N.; Pan, W.; Ekenberg, U.; Gvozdić, D. M.; Boubanga-Tombet, S.; Upadhya, P. C.; Reno, J.; Taylor, A. J.; Prasankumar, R. P.

    2015-01-21

    Two-dimensional hole gases (2DHGs) have attracted recent attention for their unique quantum physics and potential applications in areas including spintronics and quantum computing. However, their properties remain relatively unexplored, motivating the use of different techniques to study them. We then used terahertz magneto-optical spectroscopy to investigate the cyclotron resonance frequency in a high mobility 2DHG, revealing a nonlinear dependence on the applied magnetic field. This is shown to be due to the complex non-parabolic valence band structure of the 2DHG, as verified by multiband Landau level calculations. We also found that impurity scattering dominates cyclotron resonance decay in the 2DHG,more » in contrast with the dominance of superradiant damping in two-dimensional electron gases. Our results shed light on the properties of 2DHGs, motivating further studies of these unique 2D nanosystems.« less

  9. Measuring the Elasticity of Poly‐l‐Proline Helices with Terahertz Spectroscopy

    PubMed Central

    Ruggiero, Michael T.; Sibik, Juraj; Orlando, Roberto; Zeitler, J. Axel

    2016-01-01

    Abstract The rigidity of poly‐l‐proline is an important contributor to the stability of many protein secondary structures, where it has been shown to strongly influence bulk flexibility. The experimental Young's moduli of two known poly‐l‐proline helical forms, right‐handed all‐cis (Form I) and left‐handed all‐trans (Form II), were determined in the crystalline state by using an approach that combines terahertz time‐domain spectroscopy, X‐ray diffraction, and solid‐state density functional theory. Contrary to expectations, the helices were found to be considerably less rigid than many other natural and synthetic polymers, as well as differing greatly from each other, with Young's moduli of 4.9 and 9.6 GPa for Forms I and II, respectively. PMID:27121300

  10. Degradation diagnosis of ultrahigh-molecular weight polyethylene with terahertz-time-domain spectroscopy

    SciTech Connect

    Yamamoto, Kohji; Yamaguchi, Mariko; Tani, Masahiko; Hangyo, Masanori; Teramura, Satoshi; Isu, Toshiro; Tomita, Naohide

    2004-11-29

    We investigated ultrahigh-molecular-weight-polyethylene (UHMWPE) samples prepared by various conditions with terahertz-time-domain spectroscopy (THz-TDS). Degradation of the virgin UHMWPE samples by {gamma} irradiation induced a drastic increase of the absorption ranging continuously over the THz region. The increase of the absorption continuum is interpreted to originate in the oxidation of the amorphous region within the sample. Only slight THz spectral changes induced by the {gamma} irradiation were, however, observed for the UHMWPE samples doped with 0.1 and 0.3 wt % vitamin E. This result agrees with the earlier indication that vitamin E has an antidegradation effect on UHMWPE. The present result shows that the THz-TDS can be used for the quality control of UHMWPE by monitoring the absorption continuum in the THz region.

  11. Magnetization-free measurements of spin orientations in orthoferrites using terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Suemoto, Tohru; Nakamura, Keita; Kurihara, Takayuki; Watanabe, Hiroshi

    2015-07-01

    The spin orientation during spin reorientation phase transition in a weak ferromagnetic orthoferrite DyxEr1-xFeO3 (x = 0.7) has been studied by using terahertz time domain spectroscopy under zero and weak external magnetic fields. The spin orientation angle was deduced from the ratio of the absorption intensity of quasi-ferromagnetic and quasi-antiferromagnetic modes, which appear around 0.25 and 0.4 THz, respectively. Between 11.4 and 17.9 K, this material showed a rotation-type reorientation transition rather than Morin-type transition. The temperature and magnetic field dependence of the orientation angle of the magnetic moment was found to follow a simple model assuming a linear temperature dependence of the anisotropy parameter. It has been also shown that this method is insensitive to the domain structure with opposite polarity and that it allows measurement without macroscopic magnetization.

  12. Density Detection of Aligned Nanowire Arrays Using Terahertz Time-Domain Spectroscopy.

    PubMed

    Xiang, Wenfeng; Wang, Xin; Liu, Yuan; Zhang, JiaQi; Zhao, Kun

    2016-12-01

    A rapid technique is necessary to quantitatively detect the density of nanowire (NW) and nanotube arrays in one-dimensional devices which have been identified as useful building blocks for nanoelectronics, optoelectronics, biomedical devices, etc. Terahertz (THz) time-domain spectroscopy was employed in this research to detect the density of aligned Ni NW arrays. The transmitted amplitude of THz peaks and optical thickness of NW arrays was found to be the effective parameters to analyze the density change of NW arrays. Owing to the low multiple scattering and high order of Ni NW arrays, a linear relationship was observed for the transmitted amplitude and optical thickness regarding NW density, respectively. Therefore, THz technique may be used as a promising tool to characterize the density of one-dimensional structures in the large-scale integrated nanodevice fabrication. PMID:27431495

  13. Terahertz spectroscopy of brain tissue from a mouse model of Alzheimer's disease

    NASA Astrophysics Data System (ADS)

    Shi, Lingyan; Shumyatsky, Pavel; Rodríguez-Contreras, Adrián; Alfano, Robert

    2016-01-01

    The terahertz (THz) absorption and index of refraction of brain tissues from a mouse model of Alzheimer's disease (AD) and a control wild-type (normal) mouse were compared using THz time-domain spectroscopy (THz-TDS). Three dominating absorption peaks associated to torsional-vibrational modes were observed in AD tissue, at about 1.44, 1.8, and 2.114 THz, closer to the peaks of free tryptophan molecules than in normal tissue. A possible reason is that there is more free tryptophan in AD brain tissue, while in normal brain tissue more tryptophan is attached to other molecules. Our study suggests that THz-absorption modes may be used as an AD biomarker fingerprint in brain, and that THz-TDS is a promising technique for early diagnosis of AD.

  14. Rapid determination of saponification value and polymer content of vegetable and fish oils by terahertz spectroscopy.

    PubMed

    Jiang, Feng Ling; Ikeda, Ikuo; Ogawa, Yuichi; Endo, Yasushi

    2012-01-01

    A rapid method for determining the saponification value (SV) and polymer content of vegetable and fish oils using the terahertz (THz) spectroscopy was developed. When the THz absorption spectra for vegetable and fish oils were measured in the range of 20 to 400 cm⁻¹, two peaks were seen at 77 and 328 cm⁻¹. The level of absorbance at 77 cm⁻¹ correlated well with the SV. When the THz absorption spectra of thermally treated high-oleic safflower oils were measured, the absorbance increased with heating time. The polymer content in thermally treated oil correlated with the absorbance at 77 cm⁻¹. These results demonstrate that the THz spectrometry is a suitable non-destructive technique for the rapid determination of the SV and polymer content of vegetable and fish oils. PMID:23018850

  15. Carrier dynamics of rubrene single-crystals revealed by transient broadband terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Yada, H.; Uchida, R.; Sekine, H.; Terashige, T.; Tao, S.; Matsui, Y.; Kida, N.; Fratini, S.; Ciuchi, S.; Okada, Y.; Uemura, T.; Takeya, J.; Okamoto, H.

    2014-10-01

    Carrier dynamics of an organic molecular semiconductor, rubrene, was investigated by optical-pump terahertz-probe spectroscopy from 1 to 15 THz. At 294 K, a Drude-like response due to photogenerated hole carriers is observed below 8 THz. The real part σ 1 ( ω ) of the optical conductivity is suppressed below 2 THz, indicating the presence of a localization effect. Such a spectral feature was reproduced by a Drude-Anderson model including the effect of dynamical disorder due to intermolecular vibrations. At 50 K, the spectral weight of σ 1 ( ω ) due to photocarriers shifts to lower frequency below 4 THz and the suppression of σ 1 ( ω ) is hardly observed, which we associate with a reduction of thermal molecular motions. The overall photocarrier generation and recombination dynamics is also discussed.

  16. Application of terahertz absorption spectroscopy to evaluation of aging variation of medicine.

    PubMed

    Kawase, Masaya; Saito, Tadashi; Ogawa, Masafumi; Uejima, Hideki; Hatsuda, Yasutoshi; Kawanishi, Sonoyo; Hirotani, Yoshihiko; Myotoku, Michiaki; Ikeda, Kenji; Konishi, Hiroki; Iga, Ikumi; Yamakawa, Junji; Nishizawa, Seizi; Yamamoto, Kohji; Tani, Masahiko

    2011-01-01

    The absorption spectra of three kinds of medicines both before and after the expiration date: Amlodin OD(®) (5 mg), Basen OD(®) (0.2 mg) and Gaster D(®) (10 mg) have been measured by terahertz time domain spectroscopy (THz-TDS). All the medicines show some differences in the THz absorption spectra between medicines before and after the expiration dates. X-Ray powder diffraction (XRD) studies of all medicines suggest that the polymorph of the main effective compound is not changed before and after the expiration date. Therefore, the differences in the THz spectra between medicines before and after the expiration dates arise from aging variation of diluting agents and/or from modifications of intermolecular interaction between the effective compounds and diluting agents. PMID:21321447

  17. Electron density measurement of inductively coupled plasmas by terahertz time-domain spectroscopy (THz-TDS)

    SciTech Connect

    Ando, Ayumi; Kurose, Tomoko; Kitano, Katsuhisa; Hamaguchi, Satoshi; Reymond, Vivien; Kitahara, Hideaki; Takano, Keisuke; Hangyo, Masanori; Tani, Masahiko

    2011-10-01

    The electron densities of argon inductively coupled plasmas were measured by terahertz time-domain spectroscopy (THz-TDS). At a low pressure, the electron densities were also measured with a Langmuir-type double probe and the validity of THz-TDS electron-density measurement in a plasma has been corroborated. As the input radio-frequency (RF) power increases, the plasma density and gas temperature increase, which makes the probe measurement less reliable or even impossible, due to the large heat load to the probe surface. On the contrary, the THz-TDS measurement is unaffected by the gas temperature and becomes more reliable due to the higher electron density at higher input power for plasma generation.

  18. Reflectance spectroscopy of organic compounds: 1. Alkanes

    USGS Publications Warehouse

    Clark, R.N.; Curchin, J.M.; Hoefen, T.M.; Swayze, G.A.

    2009-01-01

    Reflectance spectra of the organic compounds comprising the alkane series are presented from the ultraviolet to midinfrared, 0.35 to 15.5 /??m. Alkanes are hydrocarbon molecules containing only single carbon-carbon bonds, and are found naturally on the Earth and in the atmospheres of the giant planets and Saturn's moon, Titan. This paper presents the spectral properties of the alkanes as the first in a series of papers to build a spectral database of organic compounds for use in remote sensing studies. Applications range from mapping the environment on the Earth, to the search for organic molecules and life in the solar system and throughout the. universe. We show that the spectral reflectance properties of organic compounds are rich, with major diagnostic spectral features throughout the spectral range studied. Little to no spectral change was observed as a function of temperature and only small shifts and changes in the width of absorption bands were observed between liquids and solids, making remote detection of spectral properties throughout the solar system simpler. Some high molecular weight organic compounds contain single-bonded carbon chains and have spectra similar to alkanes even ' when they fall into other families. Small spectral differences are often present allowing discrimination among some compounds, further illustrating the need to catalog spectral properties for accurate remote sensing identification with spectroscopy.

  19. Probing charge transfer and hot carrier dynamics in organic solar cells with terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Cunningham, Paul D.; Lane, Paul A.; Melinger, Joseph S.; Esenturk, Okan; Heilweil, Edwin J.

    2016-04-01

    Time-resolved terahertz spectroscopy (TRTS) was used to explore charge generation, transfer, and the role of hot carriers in organic solar cell materials. Two model molecular photovoltaic systems were investigated: with zinc phthalocyanine (ZnPc) or alpha-sexathiophene (α-6T) as the electron donors and buckminsterfullerene (C60) as the electron acceptor. TRTS provides charge carrier conductivity dynamics comprised of changes in both population and mobility. By using time-resolved optical spectroscopy in conjunction with TRTS, these two contributions can be disentangled. The sub-picosecond photo-induced conductivity decay dynamics of C60 were revealed to be caused by auto-ionization: the intrinsic process by which charge is generated in molecular solids. In donor-acceptor blends, the long-lived photo-induced conductivity is used for weight fraction optimization of the constituents. In nanoscale multilayer films, the photo-induced conductivity identifies optimal layer thicknesses. In films of ZnPc/C60, electron transfer from ZnPc yields hot charges that localize and become less mobile as they thermalize. Excitation of high-lying Franck Condon states in C60 followed by hole-transfer to ZnPc similarly produces hot charge carriers that self-localize; charge transfer clearly precedes carrier cooling. This picture is contrasted to charge transfer in α-6T/C60, where hole transfer takes place from a thermalized state and produces equilibrium carriers that do not show characteristic signs of cooling and self-localization. These results illustrate the value of terahertz spectroscopic methods for probing charge transfer reactions.

  20. Quantitative measurement of AMS and orange mixtures by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Qiang; Ma, Yehao; Wang, Xiaowei

    2012-06-01

    Terahertz time domain spectroscopy (THz-TDS) is a new kind of nondestructive detection method, frequency of terahertz wave spans from a few tens of GHz to several THz, which is used to detect material because of its strong identification, it can supply rich vibration information caused by intermolecular and large intra-molecular. Ammonium sulfamate (AMS) is a kind of herbicide, it has special value for many woody plants, which can prevent annual weeds. The excess use of pesticide is a huge threaten for human health in recent years, thus the research on detection of pesticide has absolutely important meaning, in this paper, pure AMS and mixture samples of AMS and orange are measured using THz-TDS, and their absorption coefficient are calculated by the model, which is put forward based on Fresnel equation. We qualitatively analyze the absorption coefficient spectra of pure AMS, which is useful for us to identify the pesticide in agriculture products. Meanwhile, we measured 14 mixture samples of AMS and orange, the weight ratio of mixtures are from 0% to 59.9%. Nine samples are considered as calibration set and the other five samples are regarded as prediction set, to quantitatively analyze the concentration of AMS by the partial least squares (PLS), the result shows that the prediction error is less then 4.5%, in addition, the relationship of the average absorption and weight ratio are absolutely linear. The experiment demonstrates that THz-TDS is promising and efficient to quantitatively detect the component of mixtures, and it has important reference value for the detection of pesticide in agriculture food.

  1. Terahertz dielectric response of photoexcited carriers in Si revealed via single-shot optical-pump and terahertz-probe spectroscopy

    SciTech Connect

    Minami, Yasuo; Horiuchi, Kohei; Masuda, Kaisei; Takeda, Jun; Katayama, Ikufumi

    2015-10-26

    We have demonstrated accurate observations of terahertz (THz) dielectric response due to photoexcited carriers in a Si plate via single-shot optical-pump and THz-probe spectroscopy. In contrast to conventional THz time-domain spectroscopy, this spectroscopic technique allows single-shot detection of the THz response of materials at a given delay time between the pump and THz pulses, thereby sufficiently extending the time interval between the pump pulses. As a result, we can accurately measure the dielectric properties of materials, while avoiding artifacts in the response caused by the accumulation of long-lived photoexcited carriers. Using our single-shot scheme, the transmittance of a Si plate was measured in the range of 0.5–2.5 THz with different pump fluences. Based on a Drude model analysis, the optically induced complex dielectric constant, plasma frequency, and damping rate in the THz region were quantitatively evaluated.

  2. Terahertz time domain spectroscopy allows contactless monitoring of grapevine water status

    PubMed Central

    Santesteban, Luis G.; Palacios, Inés; Miranda, Carlos; Iriarte, Juan C.; Royo, José B.; Gonzalo, Ramón

    2015-01-01

    Agriculture is the sector with the greatest water consumption, since food production is frequently based on crop irrigation. Proper irrigation management requires reliable information on plant water status, but all the plant-based methods to determine it suffer from several inconveniences, mainly caused by the necessity of destructive sampling or of alteration of the plant organ due to contact installation. The aim of this work is to test if terahertz (THz) time domain reflectance measurements made on the grapevine trunk allows contactless monitoring of plant status. The experiments were performed on a potted 14-years-old plant, using a general purpose THz emitter receiver head. Trunk THz time-domain reflection signal proved to be very sensitive to changes in plant water availability, as its pattern follows the trend of soil water content and trunk growth variations. Therefore, it could be used to contactless monitor plant water status. Apart from that, THz reflection signal was observed to respond to light conditions which, according to a specifically designed girdling experiment, was caused by changes in the phloem. This latter results opens a promising field of research for contactless monitoring of phloem activity. PMID:26082791

  3. Terahertz time domain spectroscopy allows contactless monitoring of grapevine water status.

    PubMed

    Santesteban, Luis G; Palacios, Inés; Miranda, Carlos; Iriarte, Juan C; Royo, José B; Gonzalo, Ramón

    2015-01-01

    Agriculture is the sector with the greatest water consumption, since food production is frequently based on crop irrigation. Proper irrigation management requires reliable information on plant water status, but all the plant-based methods to determine it suffer from several inconveniences, mainly caused by the necessity of destructive sampling or of alteration of the plant organ due to contact installation. The aim of this work is to test if terahertz (THz) time domain reflectance measurements made on the grapevine trunk allows contactless monitoring of plant status. The experiments were performed on a potted 14-years-old plant, using a general purpose THz emitter receiver head. Trunk THz time-domain reflection signal proved to be very sensitive to changes in plant water availability, as its pattern follows the trend of soil water content and trunk growth variations. Therefore, it could be used to contactless monitor plant water status. Apart from that, THz reflection signal was observed to respond to light conditions which, according to a specifically designed girdling experiment, was caused by changes in the phloem. This latter results opens a promising field of research for contactless monitoring of phloem activity. PMID:26082791

  4. Terahertz Time-Domain Spectroscopy of Thermoresponsive Polymers in Aqueous Solution.

    PubMed

    Serin, Guillaume; Nguyen, Hong Hanh; Marty, Jean-Daniel; Micheau, Jean-Claude; Gernigon, Véronique; Mingotaud, Anne-Françoise; Bajon, Damienne; Soulet, Thierry; Massenot, Sébastien; Coudret, Christophe

    2016-09-15

    The behavior of highly concentrated aqueous solutions of two thermoresponsive polymers poly(N-isopropylacrylamide) (PNIPAm) and poly(N-vinylcaprolactam) (PVCL) have been investigated by terahertz time-domain spectroscopy (THz-TDS). Measurements have been performed for concentrations up to 20 wt %, over a frequency range from 0.3 to 1.5 THz and for temperatures from 20 to 45 °C including the zone for lower critical solution temperature (LCST). THz-TDS enables the study of the behavior of water present in the solution (i.e., free or bound to the polymer). From these measurements, in addition to phase transition temperature, thermodynamic data such as variation of enthalpy and entropy can be inferred. Thanks to these data, further insights upon the mechanism involved during the dehydration phenomenon were obtained. These results were compared to the ones issued from dynamic light scattering, spectroscopy, or microscopy techniques to underline the interest to use THz-TDS as a powerful tool to characterize the behavior of thermoresponsive polymers in highly concentrated solutions. PMID:27490372

  5. Process analytical technology (PAT): quantification approaches in terahertz spectroscopy for pharmaceutical application.

    PubMed

    Wu, Huiquan; Heilweil, Edwin J; Hussain, Ajaz S; Khan, Mansoor A

    2008-02-01

    Terahertz (THz) spectroscopy and chemometric analysis of resultant absorption spectra in the 30-500 cm(-1) range has been applied to perform quantitative determination of both active ingredient and excipient concentrations of tablets. Tests were performed on a series of tablets composed of various concentrations and processes of theophylline formulated with lactose, magnesium stearate, starch or Avicel, and as a function of tablet hardness. Transmission spectra of polyethylene pellets derived from each of the samples were analyzed using three approaches. Spectral superposition method was used as an indirect measure to examine whether and when the interaction among various pharmaceutical components and the tableting history could be considered insignificant for quantification purpose. Spectral characteristic peak method was able to correlate peak maxima with correction for tablets having the same hardness. Multivariate analysis (PCR and PLS 1) was capable of correlating THz spectra with tablet concentrations. The predicted concentrations of independent samples using multivariate models agreed well with nominal concentrations. The best correlations were obtained using multivariate analysis. With these studies, the advantage of using multivariate approach was demonstrated for process analytical technology (PAT) application. Further, the feasibility of integrating THz spectroscopy and chemometrics for the purpose of quantifying pharmaceutical tablet concentrations was demonstrated. PMID:17722101

  6. Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers

    PubMed Central

    Yasui, Takeshi; Ichikawa, Ryuji; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

    2015-01-01

    Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers. PMID:26035687

  7. Preliminary study on quality evaluation of pecans with terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Bin; Cao, Wei; Mathanker, Sunil; Zhang, Weili; Wang, Ning

    2010-11-01

    This paper reports a preliminary work on a feasibility study of applying terahertz (THz) technology for pecan quality evaluation. A set of native pecan nuts collected in 2009 were used during the experiment. Each pecan nutmeat was manually sliced at a thickness of about 1mm, 2mm, and 3mm and a size of about 2cm (length) ×1cm (width). Pecan shell and inner separator were also cut into the same size. The absorption spectra for the nutmeat slices, shell, and inner separator were collected using a THz time-domain spectroscopy (THz-TDS) developed by a group of researchers at Oklahoma State University. The test results show that nutmeat, shell, and inner separator had different absorption characteristics within the bandwidth of 0.2-2.0 THz. To study the capability of insect damage detection of the THz spectroscopy, the absorption spectra of insects (living manduca sexta and dry pecan weevil) were also collected. Due to high water contents in the insects, very obvious spectral characteristics were found. The results from the preliminary study show a potential of THz technology applied for quality detection of bio-products. However, since bio-products mostly have high water content and are handled under an environment with certain levels of water content, practical issues needs to be further investigated to make the THz technology a feasible tool for quality evaluation.

  8. Application of terahertz spectroscopy imaging for discrimination of transgenic rice seeds with chemometrics.

    PubMed

    Liu, Wei; Liu, Changhong; Hu, Xiaohua; Yang, Jianbo; Zheng, Lei

    2016-11-01

    Discrimination of genetically modified organisms is increasingly demanded by legislation and consumers worldwide. The feasibility of a non-destructive discrimination of transgenic rice seeds from its non-transgenic counterparts was examined by terahertz spectroscopy imaging system combined with chemometrics. Principal component analysis (PCA), least squares support vector machines (LS-SVM), PCA-back propagation neural network (PCA-BPNN), and random forest (RF) models with the first and second derivative and standard normal variate transformation (SNV) pre-treatments were applied to classify rice seeds based on genotype. The results demonstrated that differences between non-transgenic and transgenic rice seeds did exist, and an excellent classification (accuracy was 96.67% in the prediction set) could be achieved using the RF model combined with the first derivative pre-treatment. The results indicated that THz spectroscopy imaging together with chemometrics would be a promising technique to identify transgenic rice seeds with high efficiency and without any sample preparation. PMID:27211665

  9. Feasibility of using terahertz spectroscopy to detect seven different pesticides in wheat flour.

    PubMed

    Maeng, Inhee; Baek, Seung Hyun; Kim, Hwa Yeon; Ok, Gyeong-Sik; Choi, Sung-Wook; Chun, Hyang Sook

    2014-12-01

    This study investigated the feasibility of detecting pesticides using terahertz (THz) spectroscopy in high-density polyethylene and/or wheat flour mixtures. The absorption spectra of seven pesticides (dicofol, chlorpyrifos, chlorpyrifos-methyl, daminozide, imidacloprid, diethyldithiocarbamate, and dimethyldithiocarbamate) were measured in the frequency range 0.1 to 3 THz at room temperature. Five of the seven pesticides exhibited specific absorption peaks in the low-energy THz range. The two remaining pesticides had no specific absorption peaks in this frequency range, but they exhibited different frequency-dependent refractive indices. The absorption coefficients of imidacloprid increased with its increasing weight ratio in high-density polyethylene, and the fitted power absorptions and refractive indices using a Maxwell-Garnett effective medium model were comparable to the measured data. Imidacloprid was also identified from its characteristic absorption peaks in wheat flour mixtures, and a linear relationship between the absorption coefficient and the weight ratio was observed. Our results show the potential of detection of selected pesticides in foods, such as wheat flour, using THz spectroscopy. PMID:25474054

  10. Standoff Detection of Hidden Explosives and Cold and Fire Arms by Terahertz Time-Domain Spectroscopy and Active Spectral Imaging (Review)

    NASA Astrophysics Data System (ADS)

    Skvortsov, L. A.

    2014-11-01

    Terahertz time-domain spectroscopy and standoff spectral imaging for detection of explosives and cold and fire arms hidden, for example, under clothing, were reviewed. Special attention was paid to different schemes for practical implementation of these methods. Progress in this direction and existing problems and the prospects for their solution were discussed. Issues related to sources and receivers of terahertz radiation were briefly discussed. It was noted that interest in quantum-cascade lasers as compact sources of terahertz radiation and the potential of using them at room temperature were increasing.

  11. EDITORIAL: Terahertz nanotechnology Terahertz nanotechnology

    NASA Astrophysics Data System (ADS)

    Demming, Anna; Tonouchi, Masayoshi; Reno, John L.

    2013-05-01

    A useful synergy is being established between terahertz research and nanotechnology. High power sources [1-3] and detectors [4] in what was once considered the terahertz 'frequency gap' [5] in the electromagnetic spectrum have stimulated research with huge potential benefits in a range of industries including food, medicine and security, as well as fundamental physics and astrophysics. This special section, with guest editors Masayoshi Tonouchi and John Reno, gives a glimpse of the new horizons nanotechnology is broaching in terahertz research. While the wavelengths relevant to the terahertz domain range from hundreds of micrometres to millimetres, structures at the nanoscale reveal interesting low energy dynamics in this region. As a result terahertz spectroscopy techniques are becoming increasingly important in nanomaterial characterization, as demonstrated in this special section by colleagues at the University of Oxford in the UK and the Australian National University. They use terahertz spectroscopy to identify the best nanostructure parameters for specific applications [6]. The low energy dynamics in nanostructures also makes them valuable tools for terahertz detection [7]. In addition the much sought after terahertz detection over broadband frequency ranges has been demonstrated, providing versatility that has been greatly in demand, particularly in spectroscopy applications [8, 9]. Also in this special section, researchers in Germany and China tackle some of the coupling issues in terahertz time domain spectroscopy with an emitter specifically well suited for systems operated with an amplified fibre [3]. 'In medical imaging, the advantage of THz radiation is safety, because its energy is much lower than the ionization energy of biological molecules, in contrast to hazardous x-ray radiation,' explains Joo-Hiuk Son from the University of Seoul in Korea in his review [10]. As he also points out, the rotational and vibrational energies of water molecules are

  12. EDITORIAL: Terahertz nanotechnology Terahertz nanotechnology

    NASA Astrophysics Data System (ADS)

    Demming, Anna; Tonouchi, Masayoshi; Reno, John L.

    2013-05-01

    A useful synergy is being established between terahertz research and nanotechnology. High power sources [1-3] and detectors [4] in what was once considered the terahertz 'frequency gap' [5] in the electromagnetic spectrum have stimulated research with huge potential benefits in a range of industries including food, medicine and security, as well as fundamental physics and astrophysics. This special section, with guest editors Masayoshi Tonouchi and John Reno, gives a glimpse of the new horizons nanotechnology is broaching in terahertz research. While the wavelengths relevant to the terahertz domain range from hundreds of micrometres to millimetres, structures at the nanoscale reveal interesting low energy dynamics in this region. As a result terahertz spectroscopy techniques are becoming increasingly important in nanomaterial characterization, as demonstrated in this special section by colleagues at the University of Oxford in the UK and the Australian National University. They use terahertz spectroscopy to identify the best nanostructure parameters for specific applications [6]. The low energy dynamics in nanostructures also makes them valuable tools for terahertz detection [7]. In addition the much sought after terahertz detection over broadband frequency ranges has been demonstrated, providing versatility that has been greatly in demand, particularly in spectroscopy applications [8, 9]. Also in this special section, researchers in Germany and China tackle some of the coupling issues in terahertz time domain spectroscopy with an emitter specifically well suited for systems operated with an amplified fibre [3]. 'In medical imaging, the advantage of THz radiation is safety, because its energy is much lower than the ionization energy of biological molecules, in contrast to hazardous x-ray radiation,' explains Joo-Hiuk Son from the University of Seoul in Korea in his review [10]. As he also points out, the rotational and vibrational energies of water molecules are

  13. Ultrahigh photoconductivity of bandgap-graded CdSxSe1‑x nanowires probed by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Hongwei; Lu, Junpeng; Yang, Zongyin; Teng, Jinghua; Ke, Lin; Zhang, Xinhai; Tong, Limin; Sow, Chorng Haur

    2016-06-01

    Superiorly high photoconductivity is desirable in optoelectronic materials and devices for information transmission and processing. Achieving high photoconductivity via bandgap engineering in a bandgap-graded semiconductor nanowire has been proposed as a potential strategy. In this work, we report the ultrahigh photoconductivity of bandgap-graded CdSxSe1‑x nanowires and its detailed analysis by means of ultrafast optical-pump terahertz-probe (OPTP) spectroscopy. The recombination rates and carrier mobility are quantitatively obtained via investigation of the transient carrier dynamics in the nanowires. By analysis of the terahertz (THz) spectra, we obtain an insight into the bandgap gradient and band alignment to carrier transport along the nanowires. The demonstration of the ultrahigh photoconductivity makes bandgap-graded CdSxSe1‑x nanowires a promising candidate as building blocks for nanoscale electronic and photonic devices.

  14. Biomolecular solvation study of proteins in liquid water by a wide range gigahertz-to-terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Charkhesht, Ali; George, Deepu; Nguyen, Vinh

    Solvent dynamics within biomolecular solvation layers play a major role in enzyme activity, but obtaining an accurate and quantitative picture of solvent activity around proteins is challenging. Due to the strong absorption of water in the gigahertz-to-terahertz frequencies, it is challenging to study properties of the solvent dynamics as well as conformational changes protein in water. We have developed a highly sensitive dielectric gigahertz-to-terahertz frequency-domain spectroscopy system for probing the collective dynamics of proteins and solvent. Using this technique, we investigate the complex dielectric response of bovine serum albumin and lysozyme proteins in aqueous environment on a wide frequency range from 0.1 GHz up to 2 THz. We explore the conformation flexibility of proteins and compare the hydration dynamics around proteins to understand the effects of surface-mediated solvent dynamics, relationships among different measures of interfacial solvent dynamics, and protein-mediated solvent dynamics.

  15. Ultrahigh photoconductivity of bandgap-graded CdSxSe1−x nanowires probed by terahertz spectroscopy

    PubMed Central

    Liu, Hongwei; Lu, Junpeng; Yang, Zongyin; Teng, Jinghua; Ke, Lin; Zhang, Xinhai; Tong, Limin; Sow, Chorng Haur

    2016-01-01

    Superiorly high photoconductivity is desirable in optoelectronic materials and devices for information transmission and processing. Achieving high photoconductivity via bandgap engineering in a bandgap-graded semiconductor nanowire has been proposed as a potential strategy. In this work, we report the ultrahigh photoconductivity of bandgap-graded CdSxSe1−x nanowires and its detailed analysis by means of ultrafast optical-pump terahertz-probe (OPTP) spectroscopy. The recombination rates and carrier mobility are quantitatively obtained via investigation of the transient carrier dynamics in the nanowires. By analysis of the terahertz (THz) spectra, we obtain an insight into the bandgap gradient and band alignment to carrier transport along the nanowires. The demonstration of the ultrahigh photoconductivity makes bandgap-graded CdSxSe1−x nanowires a promising candidate as building blocks for nanoscale electronic and photonic devices. PMID:27263861

  16. Intrinsic carrier scattering mechanism in anatase Ti O2 investigated by ultraviolet-pump terahertz-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Matsui, Y.; Terashige, T.; Uchida, R.; Miyamoto, T.; Yada, H.; Matsuzaki, H.; Li, B.-S.; Sawa, A.; Okamoto, H.

    2016-07-01

    We measured the optical conductivity σ ˜(ω ) spectra caused by photocarriers in anatase Ti O2 by applying ultraviolet-pump terahertz-probe spectroscopy on epitaxially grown thin films. Drude model analyses of σ ˜(ω ) spectra reveal that, in the terahertz region, the reduced mass (m ̂) of the carriers is greater and their damping constant (γ ) is smaller than those in the infrared region. With regard to the extended Drude model, these differences can be attributed to the frequency dependence of m ̂ and γ originating from carrier-phonon scatterings. Furthermore, the interaction between carriers and Ti-O stretching modes in the 500 -1000 -c m-1 region strongly influences the intrinsic carrier scattering mechanism in anatase Ti O2 .

  17. Ultrahigh photoconductivity of bandgap-graded CdSxSe1-x nanowires probed by terahertz spectroscopy.

    PubMed

    Liu, Hongwei; Lu, Junpeng; Yang, Zongyin; Teng, Jinghua; Ke, Lin; Zhang, Xinhai; Tong, Limin; Sow, Chorng Haur

    2016-06-06

    Superiorly high photoconductivity is desirable in optoelectronic materials and devices for information transmission and processing. Achieving high photoconductivity via bandgap engineering in a bandgap-graded semiconductor nanowire has been proposed as a potential strategy. In this work, we report the ultrahigh photoconductivity of bandgap-graded CdSxSe1-x nanowires and its detailed analysis by means of ultrafast optical-pump terahertz-probe (OPTP) spectroscopy. The recombination rates and carrier mobility are quantitatively obtained via investigation of the transient carrier dynamics in the nanowires. By analysis of the terahertz (THz) spectra, we obtain an insight into the bandgap gradient and band alignment to carrier transport along the nanowires. The demonstration of the ultrahigh photoconductivity makes bandgap-graded CdSxSe1-x nanowires a promising candidate as building blocks for nanoscale electronic and photonic devices.

  18. Comparative study of boson peak in normal and secondary alcohols with terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Yomogida, Yoshiki; Sato, Yuki; Nozaki, Ryusuke; Mishina, Tomobumi; Nakahara, Jun'ichiro

    2010-05-01

    Using terahertz (THz) time-domain spectroscopy, we measured the complex permittivity of some normal (1-propanol, 1-butanol, and 1-pentanol) and secondary alcohols (2-propanol, 2-butanol, and 2-pentanol) in the frequency ranges from 0.2 to 2.5 THz at temperatures from 253 to 323 K. For all the samples, the complex permittivity in the THz region includes the following three components: (i) a high frequency side of dielectric relaxation processes, (ii) a broad mode around 1 THz, and (iii) a low frequency side of an intermolecular vibration mode located above 2.5 THz. The mode around 1 THz is recognized as a boson peak which is related to the local structure of disordered materials. The intensity of the boson peak in secondary alcohols is higher than that in normal alcohols. On the other hand, the number of carbon atoms slightly affects the appearance of the boson peak. These observations indicate that the position of an OH group in a molecule has a profound effect on the local structures in monohydric alcohols.

  19. Measurement of coherent terahertz radiation for time-domain spectroscopy and imaging

    NASA Astrophysics Data System (ADS)

    Kuroda, R.; Yasumoto, M.; Sei, N.; Toyokawa, H.; Ikeura-Sekiguchi, H.; Ogawa, H.; Koike, M.; Yamada, K.

    2009-12-01

    A high-power terahertz (THz) source for THz time-domain spectroscopy (THz-TDS) and THz imaging has been developed based on an S-band compact electron linac at the National Institute of Advanced Industrial Science and Technology (AIST). A THz pulse was generated as coherent synchrotron radiation (CSR) from an ultra-short electron bunch and expected to have peak power of kW-order with frequency range of 0.1-2 THz. The electro-optic (EO) sampling method with a ZnTe crystal for the THz pulse measurement has been prepared for THz-TDS system. The timing measurement between the THz pulse and a probe laser was carried out. A preliminary experiment of THz transmission imaging of an integrated circuit (IC) card has been successfully demonstrated using the THz CSR pulse and a W-band rf detector. The imaging result was experimentally compared with a result of X-ray imaging. It is confirmed that its intensity and stability are enough to perform for the THz applications.

  20. Terahertz Time-Domain Spectroscopy for In Situ Monitoring of Ceramic Nuclear Waste Forms

    NASA Astrophysics Data System (ADS)

    Clark, Braeden M.; Sundaram, S. K.

    2016-10-01

    The use of terahertz time-domain spectroscopy (THz-TDS) is presented as a non-contact method for in situ monitoring of ceramic waste forms. Single-phase materials of zirconolite (CaZrTi2O7), pyrochlore (Nd2Ti2O7), and hollandite (BaCs0.3Cr2.3Ti5.7O16 and BaCs0.3CrFeAl0.3Ti5.7O16) were characterized. The refractive index and dielectric properties in THz frequencies demonstrate the ability to distinguish between these materials. Differences in processing methods show distinct changes in both the THz-TDS spectra and optical and dielectric properties of these ceramic phases. The temperature dependence of the refractive index and relative permittivity of pyrochlore and zirconolite materials in the range of 25-200 °C is found to follow an exponential increasing trend. This can also be used to monitor the temperature of the ceramic waste forms on storage over extended geological time scales.

  1. Time-domain terahertz spectroscopy and applications on drugs and explosives

    NASA Astrophysics Data System (ADS)

    Fan, W. H.; Zhao, W.; Cheng, G. H.; Burnett, A. D.; Upadhya, P. C.; Cunningham, J. E.; Linfield, E. H.; Davies, A. G.

    2008-03-01

    Many materials of interest to the forensic and security services, such as explosives, drugs and biological agents, exhibit characteristic spectral features in the terahertz (THz) frequency range. These spectral features originate from inter-molecular interactions, involving collective motions of molecules. Broadband THz time-domain spectroscopy (THz-TDS) system have been used to analyze a number of drugs-of-abuse and explosives that are of interest to the forensic and security services. These samples ranged from crystalline powders, pressed into pellets, to thin sheets of plastic explosives, and all being measured in transmission geometry in the frequency range 0.1 - 8 THz. To well understand the nature of the observed spectral features and the effects of thermal broadening on these far-infrared signatures, temperature-dependent THz-TDS measurements have also been performed at temperatures as low as 4 K, especially for two types of cocaine. Well-resolved low-frequency absorption peaks were observed in the frequency range 0.1 - 3 THz with high resolution. Some of absorption peaks were found clearly to become more intense and shift to higher frequencies as the temperature was reduced. The results confirm that the low-frequency collective modes are highly sensitive to the structural and spatial arrangement of molecules. Furthermore, a number of common postal packaging materials made from paper, cardboard, even several types of plastic, have been tested with drug sample to assess the ability of THz-TDS in a hostile detection environment.

  2. Terahertz Spectroscopy and Global Analysis of the Bending Vibrations of Acetylene 12C2D2

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Drouin, Brian J.; Pearson, John C.; Pickett, Herbert M.; Lattanzi, Valerio; Walters, Adam

    2009-06-01

    Two hundred and fifty-one 12C2D2 transitions have been measured in the 0.2-1.6 THz region of its ν5-ν4 difference band and 202 of them were observed for the first time. The accuracy of these measurements is estimated to be ranging from 50 kHz to 100 kHz. The 12C2D2 molecules were generated under room temperature by passing 120-150 mTorr D2O vapor through calcium carbide (CaC2) powder. A multistate analysis was carried out for the bending vibrational modes ν4 and ν5 of 12C2D2, which includes the lines observed in this work and prior microwave, far-infrared and infrared data on the pure bending levels. Significantly improved molecular parameters were obtained for 12C2D2 by adding the new measurements to the old data set, which had only 10 lines with microwave measurement precision. New frequency and intensity predictions have been made based on the obtained molecular parameters. The more precise measurements and new predictions reported here will support the analyses of astronomical observations by the future high-resolution spectroscopy telescopes such as Herschel, SOFIA, and ALMA, which will work in the terahertz spectral region.

  3. TERAHERTZ SPECTROSCOPY AND GLOBAL ANALYSIS OF H{sub 3}O{sup +}

    SciTech Connect

    Yu Shanshan; Drouin, Brian J.; Pearson, John C.; Pickett, Herbert M.

    2009-01-15

    Eight ground-state inversion transitions of H{sub 3}O{sup +} in the 0.9-1.6 THz region have been measured using the frequency multiplier submillimeter spectrometer at Jet Propulsion Laboratory. The accuracy of these measurements is estimated to be 300 kHz. The ions were generated in a dc discharge through a gas mixture of a few mTorr of H{sub 2} and 30 mTorr of H{sub 2}O. A multistate analysis was carried out for H{sub 3}O{sup +}, which includes the lines observed in this work, previous submillimeter and terahertz inversion transitions in the ground state, and previous infrared data on all the four vibrational fundamental bands. Accurate molecular parameters were obtained with taking into account the strong Coriolis interaction between the symmetric OH stretching mode ({nu}{sub 1}) and the doubly degenerate asymmetric OH stretching mode ({nu}{sub 3}). Fequency predictions, particularly for high-J transitions in the ground state and in the {nu}{sub 1} and {nu}{sub 3} fundamental bands, have been greatly improved by including {approx} 200 more high-J transitions in our analysis, which were excluded in previous analyses. The more precise measurements and new predictions reported here will support the analyses of astronomical observations by the future high-resolution spectroscopy telescopes, such as Herschel, SOFIA, and ALMA.

  4. Simultaneous prediction of density and moisture content of wood by terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Inagaki, Tetsuya; Ahmed, Belal; Hartley, Ian D.; Tsuchikawa, Satoru; Reid, Matthew

    2014-11-01

    In this study, demonstration of simultaneous prediction of solid wood density and moisture content, both of which are critical in manufacturing operations, of 4 species (Aspen, Birch, Hemlock and Maple) was accomplished using terahertz time-domain spectroscopy (THz-TDS). THz measurements of wood at various moisture contents were taken for two orientations of the THz field (parallel and perpendicular) with respect to the visible grain. The real and imaginary parts of the dielectric function averaged over the frequency range of 0.1 to 0.2 THz had strong correlation with density and moisture content of the wood. We extend a model that has been applied previously to oven-dry wood to include the effects of moisture below the fiber saturation point by combining two effective medium models, which allows the dielectric function of water, air and oven-dry cell wall material to be modeled to give an effective dielectric function for the wood. A strong correlation between measured and predicted values for density and moisture content were observed.

  5. Dielectric Study of Alcohols Using Broadband Terahertz Time Domain Spectroscopy (THz-TDS).

    NASA Astrophysics Data System (ADS)

    Sarkar, Sohini; Saha, Debasis; Banerjee, Sneha; Mukherjee, Arnab; Mandal, Pankaj

    2016-06-01

    Broadband Terahertz-Time Domain Spectroscopy (THz-TDS) (1-10 THz) has been utilized to study the complex dielectric properties of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 1-octanol. Previous reports on dielectric study of alcohols were limited to 5 THz. At THz (1 THz = 33.33 wn = 4 meV) frequency range (0.1 to 15 THz), the molecular reorientation and several intermolecular vibrations (local oscillation of dipoles) may coexist and contribute to the overall liquid dynamics. We find that the Debye type relaxations barely contribute beyond 1 THz, rather three harmonic oscillators dominate the entire spectral range. To get insights on the modes responsible for the observed absorption in THz frequency range, we performed all atom molecular dynamics (MD) using OPLS force field and ab initio quantum calculations. Combined experimental and theoretical study reveal that the complex dielectric functions of alcohols have contribution from a) alkyl group oscillation within H-bonded network ( 1 THz), b) intermolecular H-bond stretching ( 5 THz) , and c) librational motions in alcohols. The present work, therefore, complements all previous studies on alcohols at lower frequencies and provides a clear picture on them in a broad spectral range from microwave to 10 THz.

  6. Magnetization-free measurements of spin orientations in orthoferrites using terahertz time domain spectroscopy

    SciTech Connect

    Suemoto, Tohru Nakamura, Keita; Kurihara, Takayuki; Watanabe, Hiroshi

    2015-07-27

    The spin orientation during spin reorientation phase transition in a weak ferromagnetic orthoferrite Dy{sub x}Er{sub 1−x}FeO{sub 3} (x = 0.7) has been studied by using terahertz time domain spectroscopy under zero and weak external magnetic fields. The spin orientation angle was deduced from the ratio of the absorption intensity of quasi-ferromagnetic and quasi-antiferromagnetic modes, which appear around 0.25 and 0.4 THz, respectively. Between 11.4 and 17.9 K, this material showed a rotation-type reorientation transition rather than Morin-type transition. The temperature and magnetic field dependence of the orientation angle of the magnetic moment was found to follow a simple model assuming a linear temperature dependence of the anisotropy parameter. It has been also shown that this method is insensitive to the domain structure with opposite polarity and that it allows measurement without macroscopic magnetization.

  7. Distinguishing Gasoline Engine Oils of Different Viscosities Using Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Adbul-Munaim, Ali Mazin; Reuter, Marco; Koch, Martin; Watson, Dennis G.

    2015-07-01

    Terahertz-time-domain spectroscopy (THz-TDS) in the range of 0.5-2.0 THz was evaluated for distinguishing among gasoline engine oils of three different grades (SAE 5W-20, 10W-40, and 20W-50) from the same manufacturer. Absorption coefficient showed limited potential and only distinguished ( p < 0.05) the 20W-50 grade from the other two grades in the 1.7-2.0-THz range. Refractive index data demonstrated relatively flat and consistently spaced curves for the three oil grades. ANOVA results confirmed a highly significant difference ( p < 0.0001) in refractive index among each of the three oils across the 0.5-2.0-THz range. Linear regression was applied to refractive index data at 0.25-THz intervals from 0.5 to 2.0 THz to predict kinematic viscosity. All seven linear regression models, intercepts, and refractive index coefficients were highly significant ( p < 0.0001). All models had a similar fit with R 2 ranging from 0.9773 to 0.9827 and RMSE ranging from 6.33 to 7.75. The refractive indices at 1.25 THz produced the best fit. The refractive indices of these oil samples were promising for identification and distinction of oil grades.

  8. Determination of soluble solids content in apple products by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Hao, Guohui; Liu, Jianjun; Hong, Zhi

    2011-08-01

    Soluble solids content is an important index for fruit quality. One of the traditional methods in determining soluble solids content of fruits is refractometry which measures the refractive index in visible or near infrared. Here we reported the use of terahertz time-domain transmission spectroscopy (THz-TDTS) technique for the determination of soluble solids content in apple products. Not only the refractive index, but also the absorption coefficient is used in regression model. In method one, sucrose solutions were for the calibration set , root mean square of validation set (RMSEP) was 0.168% for absorption coefficient model, 0.741% for refractive index model. In method two, apple products were for the calibration set, RMSEP was 0.143% for absorption coefficient model, 0.648% for refractive index model. Less absolute error of 0.2% between predicted and refractometer value has been both obtained from two methods with absorption coefficient model. This result proved the THz-TDS technique is quite potential for nondestructive detection on food quality.

  9. Characterization and Classification of Coals and Rocks Using Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Hu, Ke-xiang; Zhang, Lei; Yu, Xiao; Ding, En-jie

    2016-09-01

    Being the key unaddressed problem in unmanned mining condition, a new method for the coal-rock interface recognition was proposed in the study. Firstly, terahertz time-domain spectroscopy (THz-TDS) was employed to measure 10 kinds of coals/rocks which were common in China. Secondly, the physical properties of coals/rocks such as absorption coefficient spectra, refractive index, and dielectric properties in THz band were studied. The different responses in THz range caused by diverse components in coals/rocks were discussed, and the dielectric property of coals/rocks in THz band was well fitted by the Lorentz model. Finally, by the means of principal component analysis (PCA), support vector machine (SVM), and THz spectral data, the recognition rate of coals/rocks reaches to 100 % and the recognition rate of different bituminous coals reaches to 97.5 %. The experimental results show that the proposed method is fast, stable, and accurate for the detection of coal-rock interface and could be a promising tool for the classification of different bituminous coals.

  10. Solid Material Characterization of Freeze-Dried Gabexate Mesilate Containing D-Mannitol by Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Otsuka, Makoto; Fukura, Naomi; Abe, Hiroyuki

    2013-02-01

    The purpose of the present study is to characterize polymorphic forms and intermolecular interactions of freeze-dried pharmaceuticals containing additives by terahertz (THz) spectroscopy as a, process analytical technology tool in the pharmaceutical industry. Freeze-dried gabexate mesilate/D-mannitol products containing 17-75 mol% gabexate mesilate were obtained using a conventional freeze-dryer. Freeze-dried products and physical mixtures of gabexate mesilate and mannitol with various drug contents were characterized by X-ray powder diffraction (XRD) analysis, differential scanning calorimetry (DSC) and THz. The XRD and DSC results indicated that freeze-dried mannitol was obtained as a mixture of β and δ forms of mannitol from a plain solution, but the freeze-dried product of the gabexate mesilate/mannitol mixture consisted of crystalline gabexate mesilate and the pure δ form of mannitol. Similar to the results of XRD and DSC, THz before the freeze-drying of gabexate mesilate was almost the same as that after. In contrast, the THz of mannitol before freeze-drying had specific peaks due to the β form, but that after had peaks due to δ and β forms. To clarify the polymorphic forms of the freeze-dried products, the THz were analyzed by least squares regression. The calibration models used to predict the amounts of gabexate mesilate and mannitol had sufficient accuracy and linearity, respectively. Two decomposed THz in FGMs had specific peaks due to the δ form of mannitol or gabexate mesilate.

  11. Si-prism-array coupled terahertz-wave parametric oscillator with pump light totally reflected at the terahertz-wave exit surface.

    PubMed

    Zhang, Ruiliang; Qu, Yanchen; Zhao, Weijiang; Liu, Chuang; Chen, Zhenlei

    2016-09-01

    A Si-prism-array coupled terahertz (THz)-wave parametric oscillator with the pump totally reflected at the THz-wave exit surface (PR-Si-TPO) is demonstrated by manufacturing an 800 nm air gap between the crystal and the Si-prism array. Influence on the total reflection of the pump from the Si prisms is eliminated and efficient coupling of the THz wave is ensured by using this air gap. When the THz-wave frequency varies from 1.8 to 2.3 THz, compared with a Si-prism-array coupled TPO (Si-TPO) with the pump transmitting through the crystal directly, the THz-wave output energy is enhanced by 20-50 times, and the oscillating threshold is reduced by 10%-35%. Furthermore, the high end of the THz-wave frequency tuning range of the PR-Si-TPO is expanded to 3.66 THz compared with 2.5 THz for the Si-TPO. PMID:27607961

  12. Si-prism-array coupled terahertz-wave parametric oscillator with pump light totally reflected at the terahertz-wave exit surface.

    PubMed

    Zhang, Ruiliang; Qu, Yanchen; Zhao, Weijiang; Liu, Chuang; Chen, Zhenlei

    2016-09-01

    A Si-prism-array coupled terahertz (THz)-wave parametric oscillator with the pump totally reflected at the THz-wave exit surface (PR-Si-TPO) is demonstrated by manufacturing an 800 nm air gap between the crystal and the Si-prism array. Influence on the total reflection of the pump from the Si prisms is eliminated and efficient coupling of the THz wave is ensured by using this air gap. When the THz-wave frequency varies from 1.8 to 2.3 THz, compared with a Si-prism-array coupled TPO (Si-TPO) with the pump transmitting through the crystal directly, the THz-wave output energy is enhanced by 20-50 times, and the oscillating threshold is reduced by 10%-35%. Furthermore, the high end of the THz-wave frequency tuning range of the PR-Si-TPO is expanded to 3.66 THz compared with 2.5 THz for the Si-TPO.

  13. Technical Report: Final project report for Terahertz Spectroscopy of Complex Matter

    SciTech Connect

    R. A. Cheville; D. R. Grischkowsky

    2007-02-08

    This project designed characterization techniques for thin films of complex matter and other materials in the terahertz spectral region extending from approximately 100 GHz to 4000 GHz (4 THz) midway between radio waves and light. THz has traditionally been a difficult region of the spectrum in which to conduct spectroscopic measurements. The “THz gap” arises from the nature of the sources and detectors used in spectroscopy both at the optical (high frequency) side and electronic (low frequency) side of the gap. To deal with the extremely rapid oscillations of the electric field in this frequency region this research project adapted techniques from both the electronics and optics technologies by fabricating microscopic antennas and driving them with short optical pulses. This research technique creates nearly single cycle pulses with extremely broad spectral bandwidth that are able to cover the THz spectral range with a single measurement. The technique of THz time domain spectroscopy (THz-TDS) has seen increasing use and acceptance in laboratories over the past fifteen years. However significant technical challenges remain in order to allow THz-TDS to be applied to measurement of solid materials, particularly thin films and complex matter. This project focused on the development and adaptation of time domain THz measurement techniques to investigate the electronic properties of complex matter in the terahertz frequency region from 25 GHz to beyond 5 THz (<1 inv. cm to >165 inv. cm). This project pursued multiple tracks in adapting THz Time Domain Spectroscopy (THz-TDS) to measurement of complex matter. The first, and most important, is development of a reliable methods to characterize the complex dielectric constant of thin films with high accuracy when the wavelength of the THz radiation is much longer than the thickness of the film. We have pursued several techniques for measurement of thin films. The most promising of these are waveguide spectroscopy and

  14. Application of terahertz time-domain spectroscopy combined with chemometrics to quantitative analysis of imidacloprid in rice samples

    NASA Astrophysics Data System (ADS)

    Chen, Zewei; Zhang, Zhuoyong; Zhu, Ruohua; Xiang, Yuhong; Yang, Yuping; Harrington, Peter B.

    2015-12-01

    Terahertz time-domain spectroscopy (THz-TDS) has been utilized as an effective tool for quantitative analysis of imidacloprid in rice powder samples. Unlike previous studies, our method for sample preparation was mixing imidacloprid with rice powder instead of polyethylene. Then, terahertz time domain transmission spectra of these mixed samples were measured and the absorption coefficient spectra of the samples with frequency range extending from 0.3 to 1.7 THz were obtained. Asymmetric least square (AsLS) method was utilized to correct the slope baselines that are presented in THz absorption coefficient spectra and improve signal-to-noise ratio of THz spectra. Chemometrics methods, including partial least squares (PLS), support vector regression (SVR), interval partial least squares (iPLS), and backward interval partial least squares (biPLS), were used for quantitative model building and prediction. To achieve a reliable and unbiased estimation, bootstrapped Latin partition was chosen as an approach for statistical cross-validation. Results showed that the mean value of root mean square error of prediction (RMSEP) for PLS (0.5%) is smaller than SVR (0.7%), these two methods were based on the whole absorption coefficient spectra. In addition, PLS performed a better performance with a lower RMSEP (0.3%) based on the THz absorption coefficient spectra after AsLS baseline correction. Alternatively, two methods for variable selection, namely iPLS and biPLS, yielded models with improved predictions. Comparing with conventional PLS and SVR, the mean values of RMSEP were 0.4% (iPLS) and 0.3% (biPLS) by selecting the informative frequency ranges. The results demonstrated that an accurate quantitative analysis of imidacloprid in rice powder samples could be achieved by terahertz time-domain transmission spectroscopy combined with chemometrics. Furthermore, these results demonstrate that THz time-domain spectroscopy can be used for quantitative determinations of other

  15. Broadband terahertz time-domain spectroscopy of ferroelectric LiTaO{sub 3}: Phonon-polariton dispersion

    SciTech Connect

    Kojima, Seiji Mori, Tatsuya

    2014-11-05

    The lowest frequency IR active A{sub 1}(z) and E(x) modes of a ferroelectric congruent lithium tantalate crystal were studied by the broadband polarized Terahertz Time-Domain Spectroscopy using the coherent THz radiation from 0.2 to 6.5 THz. The dispersion relations of the real and imaginary parts of a polariton wave vector were determined from the complex extraordinary and ordinary refractive indices for the A{sub 1}(z) and E(x) symmetry phonon-polaritons, respectively. The observed complex dispersion relations of two symmetries are in agreement within the experimental uncertainty with the calculated dispersion curves by the damped harmonic oscillator model.

  16. Terahertz time-domain spectroscopy of atmospheric water vapor from 0.4 to 2.7 THz.

    SciTech Connect

    Allman, Ronald E.; Foltynowicz, Robert J.

    2005-10-01

    We conducted broadband absorption measurements of atmospheric water vapor in the ground state, X {sup 1}A{sub 1} (000), from 0.4 to 2.7 THz with a pressure broadening-limited resolution of 6.2 GHz using pulsed, terahertz time-domain spectroscopy (THz-TDS). We measured a total of seventy-two absorption lines and forty-nine lines were identified as H{sub 2}{sup 16}O resonances. All the H{sub 2}{sup 16}O lines identified were confirmed by comparing their center frequencies to experimental values available in the literature.

  17. Forensic applications of microscopical infrared internal reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Tungol, Mary W.; Bartick, Edward G.; Reffner, John A.

    1994-01-01

    Applications of microscopical infrared internal reflection spectroscopy in forensic science are discussed. Internal reflection spectra of single fibers, hairs, paint chips, vehicle rubber bumpers, photocopy toners, carbon copies, writing ink on paper, lipstick on tissue, black electrical tape, and other types of forensic evidence have been obtained. The technique is convenient, non-destructive, and may permit smeared materials to be analyzed in situ.

  18. Terahertz Imaging and Spectroscopy of Carbon-Based and Semiconductor Nanostructures

    NASA Astrophysics Data System (ADS)

    Tomaino, Joseph L.

    This thesis will cover work that I have completed relating to the field of terahertz (THz) science. My work has consisted of generating tunable, narrowband THz pulses in a table-top optical setup and using both narrow- and broadband THz pulses to study various material systems. Broadband THz pulses were used to study the transmission properties of a large-area graphene monolayer and vertically grown carbon nanotube forests. We performed raster scans to image our optically invisible graphene sample, which was clearly distinguished from its silicon substrate. From these studies, we were able to calculate the sheet conductivity/resistivity of the graphene using a contactless, non-damaging method that is immune to difficulties arising from local defects within the sample. It also opens up the possibility of studying the material properties of a sample enclosed within certain structures without having to remove the sample and/or damage the encasement. Further, we have discovered that vertically grown carbon nanotubes respond strongly to THz radiation. Preliminary simulations suggest that they respond in a very counterintuitive way and while much remains to be done before we can state with certainty exactly what is physically occurring, the prospect of uncovering such an unanticipated result is tantalizing on its own. I used difference frequency generation of orthogonal, temporally offset, chirped optical pulses to create our narrowband THz pulses. The variable time delay between these pulses was used to adjust the pulse's central frequency. THz time domain spectroscopy and calorimeter-based measurements were used to study the temporal and spectral composition and field strength of the THz pulses. These pulses, along with their broadband counterparts, were used to study electron dynamics within semiconductor nanostructures, both bare quantum wells and quantum wells grown inside of a microcavity. The dynamics of exciton and exciton-polariton polarizations were studied

  19. Detection of Methomyl, a Carbamate Insecticide, in Food Matrices Using Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Baek, Seung Hyun; Kang, Ju Hee; Hwang, Yeun Hee; Ok, Kang Min; Kwak, Kyungwon; Chun, Hyang Sook

    2016-05-01

    The aim of this study was to investigate the feasibility of detecting methomyl, a carbamate insecticide, in food matrices (wheat and rice flours) using terahertz time-domain spectroscopy (THz-TDS). In the frequency range 0.1-3 THz, the characteristic THz absorption peaks of methomyl at room temperature were detected at 1 (33.4 cm-1), 1.64 (54.7 cm-1), and 1.89 (63.0 cm-1) THz. For detailed spectral analysis, the vibrational frequency and intensity of methomyl were calculated using solid-state density functional theory to mimic molecular interactions in the solid state. Qualitatively, the simulated spectrum was in good agreement with the experimental spectrum. Analysis of the individual absorption modes revealed that all of the features in the THz spectrum of methomyl were mainly generated from intermolecular vibrations. The peak appearing at 1 THz (33.4 cm-1) was then selected and tested for its suitability as a fingerprint for detecting methomyl in food matrices. Its absorbance was dose-dependently distinguishable from that of wheat and rice flours. The calibration curve of methomyl had a regression coefficient of >0.974 and a detection limit of <3.74 %. Accuracy and precision expressed as recovery and relative standard deviation in interday repeatability were in the ranges 78.0-96.5 and 2.83-4.98 %, respectively. Our results suggest that THz-TDS can be used for the rapid detection of methomyl in foods, but its sensitivity needs to be improved.

  20. CaCO3, its reaction and carbonate rocks: terahertz spectroscopy investigation

    NASA Astrophysics Data System (ADS)

    Zhan, Honglei; Wu, Shixiang; Zhao, Kun; Bao, Rima; Xiao, Lizhi

    2016-10-01

    Carbonate-rich rocks cover a primary part of the earth’s petroleum geology reservoir. The study of carbonate has special significance and more effective study methods are now needed. In order to improve the availability of carbonate rock detection, terahertz (THz) spectroscopy was employed to investigate relevant materials in Na2CO3  +  CaCl2  =  CaCO3  +  2NaCl, which is often used to generate CaCO3. By comparing the materials composited with different ions, it can be revealed that Ca2+, \\text{CO}32- , Na+ and Cl- have respective absorption features at different frequencies. Furthermore, by utilizing a conservation equation it can be observed that the average refractive indices of Na2CO3 as well as CaCl2 equal those of CaCO3 and NaCl in the entire range. Combining the absorption and refractive effect of the materials in the reaction can comprehensively characterize the different substances and reveal the inner interaction during the reaction. THz spectra can deduce the process of molecule rearrangement in the chemical reaction of long-term rock evolution. Besides, the absorption features of the real carbonate rock collected from the nearest town of Sinan county, Guizhou province in Yunnan-Guizhou plateau validate the peaks’ central frequencies of ions and the principal components of carbonates, which can be in agreement with the SEM-EDS analysis. This research will supply a spectral tool to identify the particles in the rock and deduce an evolution of petroleum carbonate reservoir.

  1. Protein and water confined in nanometer-scale reverse micelles studied by near infrared, terahertz, and ultrafast visible spectroscopies.

    PubMed

    Murakami, Hiroshi

    2013-01-01

    Protein-containing reverse (PCR) micelles are suitable systems to study the properties of proteins and waters in a cell-like environment. A model for determining the structural parameters of PCR micelles, such as the aqueous cavity size and molecule number of water within the reverse micelle, is presented. The model is based on an important hypothesis that the structural parameters of the protein-unfilled reverse micelle do not change after solubilization of protein. I describe a procedure using near infrared spectroscopy of OH stretching vibration band of water to verify the hypothesis. Further, the terahertz (THz) absorption spectrum of myoglobin is derived from THz time-domain spectroscopy of the PCR micellar solution, and the states of waters in reverse micelles with and without protein are discussed on the basis of the structural parameters. The last topic is on internal dynamics of PCR micelles on timescales from femtoseconds to nanoseconds studied by femtosecond time-resolved fluorescence spectroscopy.

  2. Reflectance spectroscopy for evaluating hair follicle cycle

    NASA Astrophysics Data System (ADS)

    Liu, Caihua; Guan, Yue; Wang, Jianru; Zhu, Dan

    2014-02-01

    Hair follicle, as a mini-organ with perpetually cycling of telogen, anagen and catagen, provides a valuable experimental model for studying hair and organ regeneration. The transition of hair follicle from telogen to anagen is a significant sign for successful regeneration. So far discrimination of the hair follicle stage is mostly based on canonical histological examination and empirical speculation based on skin color. Hardly a method has been proposed to quantitatively evaluate the hair follicle stage. In this work, a commercial optical fiber spectrometer was applied to monitor diffuse reflectance of mouse skin with hair follicle cycling, and then the change of reflectance was obtained. Histological examination was used to verify the hair follicle stage. In comparison with the histological examination, the skin diffuse reflectance was relatively high for mouse with telogen hair follicles; it decreased once hair follicles transited to anagen stage; then it increased reversely at catagen stage. This study provided a new method to quantitatively evaluate the hair follicle stage, and should be valuable for the basic and therapeutic investigations on hair regeneration.

  3. Combined theory of reflectance and emittance spectroscopy

    NASA Technical Reports Server (NTRS)

    Hapke, Bruce

    1995-01-01

    The theory in which either or both reflected sunlight and thermally emitted radiation contribute to the power received by a detector viewing a particulate medium, such as a powder in the laboratory or a planetary regolith, is considered theoretically. This theory is of considerable interest for the interpretation of data from field or spacecraft instruments that are sensitive to the near-infrared region of the spectrum, such as NIMS (near-infrared mapping spectrometer) and VIMS (visual and infrared mapping spectrometer), as well as thermal infrared detectors.

  4. Terahertz Desorption Emission Spectroscopy (THz DES) - ‘ALMA in the Lab’

    NASA Astrophysics Data System (ADS)

    Emile Auriacombe, Olivier Bruno Jacques; Fraser, Helen; Ellison, Brian; Ioppolo, Sergio; Rea, Simon

    2016-06-01

    ALMA is revolutionising our scope to identify and locate molecules that have been desorbed from ices, particularly complex organic molecules (COMS), which provide a vital link between interstellar and prebiotic chemistry. Explaining the existence of these molecules in star-forming regions relies on an empirical understanding of the chemistry that underpins their formation:- do COMS form predominantly in the solid-phase and then desorb to the gas phase, or do only “smaller” species, radials or ions desorb and then undergo gas-phase chemical reactions to generate larger COMS?-are the rotational state populations in COMS only attributable to equilibrium chemistry, or could their formation mechanisms and desorption processes affect the rotational state occupancy of these molecules, thereby directly tying certain species to solid-state origins?We have developed a novel laboratory method - THz Desorption Emission Spectroscopy (THz-DES) that combines “traditional” laboratory astrophysics high-vacuum ice experiments with a sensitive high-spectral-resolution terahertz total-power heterodyne radiometer 1,2, partially mirroring the spectral range of ALMA band 7 (275- 373 GHz). Ices are grown in situ on a cold-plate, situated in a vacuum cell, then (thermally) desorbed. The sub-mm emission spectra of the resultant gas-phase molecules are detected as a function of time, temperature, or distance from the surface. Our first THz DES results will be shown for pure and binary ice systems including H2O, N2O and CH3OH. They show good correlation with established methods e.g. TPD, with the advantage of exploiting the molecular spectroscopy to unravel surface dynamics, state-occupancy, and unequivocal molecular identification, as well as concurrently measuring desorption barriers and molecular yields. We will extend our technique to a broader frequency range, enabling us to detect radical and ion desorption, to differentiate between A and E populations of CH3OH or ortho

  5. Terahertz Desorption Emission Spectroscopy (THz DES) – ‘ALMA in the Lab’

    NASA Astrophysics Data System (ADS)

    Emile Auriacombe, Olivier Bruno Jacques; Fraser, Helen; Ellison, Brian; Ioppolo, Sergio; Rea, Simon

    2016-06-01

    ALMA is revolutionising our scope to identify and locate molecules that have been desorbed from ices, particularly complex organic molecules (COMS), which provide a vital link between interstellar and prebiotic chemistry. Explaining the existence of these molecules in star-forming regions relies on an empirical understanding of the chemistry that underpins their formation:- do COMS form predominantly in the solid-phase and then desorb to the gas phase, or do only “smaller” species, radials or ions desorb and then undergo gas-phase chemical reactions to generate larger COMS?-are the rotational state populations in COMS only attributable to equilibrium chemistry, or could their formation mechanisms and desorption processes affect the rotational state occupancy of these molecules, thereby directly tying certain species to solid-state origins?We have developed a novel laboratory method - THz Desorption Emission Spectroscopy (THz-DES) that combines “traditional” laboratory astrophysics high-vacuum ice experiments with a sensitive high-spectral-resolution terahertz total-power heterodyne radiometer 1,2, partially mirroring the spectral range of ALMA band 7 (275– 373 GHz). Ices are grown in situ on a cold-plate, situated in a vacuum cell, then (thermally) desorbed. The sub-mm emission spectra of the resultant gas-phase molecules are detected as a function of time, temperature, or distance from the surface. Our first THz DES results will be shown for pure and binary ice systems including H2O, N2O and CH3OH. They show good correlation with established methods e.g. TPD, with the advantage of exploiting the molecular spectroscopy to unravel surface dynamics, state-occupancy, and unequivocal molecular identification, as well as concurrently measuring desorption barriers and molecular yields. We will extend our technique to a broader frequency range, enabling us to detect radical and ion desorption, to differentiate between A and E populations of CH3OH or ortho

  6. Characteristic responses of biological and nanoscale systems in the terahertz frequency range

    SciTech Connect

    Angeluts, A A; Balakin, A V; Evdokimov, M G; Ozheredov, I A; Sapozhnikov, D A; Solyankin, P M; Shkurinov, A P; Esaulkov, M N; Nazarov, M M; Cherkasova, O P

    2014-07-31

    This paper briefly examines methods for the generation of pulsed terahertz radiation and principles of pulsed terahertz spectroscopy, an advanced informative method for studies of complex biological and nanostructured systems. Some of its practical applications are described. Using a number of steroid hormones as examples, we demonstrate that terahertz spectroscopy in combination with molecular dynamics methods and computer simulation allows one to gain information about the structure of molecules in crystals. A 'terahertz colour vision' method is proposed for analysis of pulsed terahertz signals reflected from biological tissues and it is shown that this method can be effectively used to analyse the properties of biological tissues and for early skin cancer diagnosis. (laser biophotonics)

  7. Terahertz Spectroscopy of Individual Single-Walled Carbon Nanotubes as a Probe of Luttinger Liquid Physics.

    PubMed

    Chudow, Joel D; Santavicca, Daniel F; Prober, Daniel E

    2016-08-10

    Luttinger liquid theory predicts that collective electron excitations due to strong electron-electron interactions in a one-dimensional (1D) system will result in a modification of the collective charge-propagation velocity. By utilizing a circuit model for an individual metallic single-walled carbon nanotube as a nanotransmission line, it has been shown that the frequency-dependent terahertz impedance of a carbon nanotube can probe this expected 1D Luttinger liquid behavior. We excite terahertz standing-wave resonances on individual antenna-coupled metallic single-walled carbon nanotubes. The terahertz signal is rectified using the nanotube contact nonlinearity, allowing for a low-frequency readout of the coupled terahertz current. The charge velocity on the nanotube is determined from the terahertz spectral response. Our measurements show that a carbon nanotube can behave as a Luttinger liquid system with charge-propagation velocities that are faster than the Fermi velocity. Understanding what determines the charge velocity in low-dimensional conductors is important for the development of next generation nanodevices. PMID:27439013

  8. Terahertz Spectroscopy of Individual Single-Walled Carbon Nanotubes as a Probe of Luttinger Liquid Physics.

    PubMed

    Chudow, Joel D; Santavicca, Daniel F; Prober, Daniel E

    2016-08-10

    Luttinger liquid theory predicts that collective electron excitations due to strong electron-electron interactions in a one-dimensional (1D) system will result in a modification of the collective charge-propagation velocity. By utilizing a circuit model for an individual metallic single-walled carbon nanotube as a nanotransmission line, it has been shown that the frequency-dependent terahertz impedance of a carbon nanotube can probe this expected 1D Luttinger liquid behavior. We excite terahertz standing-wave resonances on individual antenna-coupled metallic single-walled carbon nanotubes. The terahertz signal is rectified using the nanotube contact nonlinearity, allowing for a low-frequency readout of the coupled terahertz current. The charge velocity on the nanotube is determined from the terahertz spectral response. Our measurements show that a carbon nanotube can behave as a Luttinger liquid system with charge-propagation velocities that are faster than the Fermi velocity. Understanding what determines the charge velocity in low-dimensional conductors is important for the development of next generation nanodevices.

  9. Assessment of skin flap viability using visible diffuse reflectance spectroscopy and auto-fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhu, Caigang; Chen, Shuo; Chui, Christopher Hoe-Kong; Liu, Quan

    2012-12-01

    The accurate assessment of skin flap viability is vitally important in reconstructive surgery. Early identification of vascular compromise increases the change of successful flap salvage. The ability to determine tissue viability intraoperatively is also extremely useful when the reconstructive surgeon must decide how to inset the flap and whether any tissue must be discarded. Visible diffuse reflectance and auto-fluorescence spectroscopy, which yield different sets of biochemical information, have not been used in the characterization of skin flap viability simultaneously to our best knowledge. We performed both diffuse reflectance and fluorescence measurements on a reverse MacFarlane rat dorsal skin flap model to identify the additional value of auto-fluorescence spectroscopy to the assessment of flap viability. Our result suggests that auto-fluorescence spectroscopy appears to be more sensitive to early biochemical changes in a failed flap than diffuse reflectance spectroscopy, which could be a valuable complement to diffuse reflectance spectroscopy for the assessment of flap viability.

  10. High spectral resolution reflectance spectroscopy of minerals

    NASA Technical Reports Server (NTRS)

    Clark, Roger N.; King, Trude V. V.; Klejwa, Matthew; Swayze, Gregg A.; Vergo, Norma

    1990-01-01

    The reflectance spectra of minerals are studied as a function of spectral resolution in the range from 0.2 to 3.0 microns. Selected absorption bands were studied at resolving powers as high as 2240. At resolving powers of approximately 1000, many OH-bearing minerals show diagnostic sharp absorptions at the resolution limit. At low resolution, some minerals may not be distinguishable, but as the resolution is increased, most can be easily identified. As the resolution is increased, many minerals show fine structure, particularly in the OH-stretching overtone region near 1.4 micron. The fine structure can enhance the ability to discriminate between minerals, and in some cases the fine structure can be used to determine elemental composition.

  11. Diffuse reflectance spectroscopy of fibrous proteins.

    PubMed

    Millington, Keith R

    2012-09-01

    UV-visible diffuse reflectance (DR) spectra of the fibrous proteins wool and feather keratin, silk fibroin and bovine skin collagen are presented. Natural wool contains much higher levels of visible chromophores across the whole visible range (700-400 nm) than the other proteins and only those above 450 nm are effectively removed by bleaching. Both oxidative and reductive bleaching are inefficient for removing yellow chromophores (450-400 nm absorbers) from wool. The DR spectra of the four UV-absorbing amino acids tryptophan, tyrosine, cystine and phenylalanine were recorded as finely ground powders. In contrast to their UV-visible spectra in aqueous solution where tryptophan and tyrosine are the major UV absorbing species, surprisingly the disulphide chromophore of solid cystine has the strongest UV absorbance measured using the DR remission function F(R)(∞). The DR spectra of unpigmented feather and wool keratin appear to be dominated by cystine absorption near 290 nm, whereas silk fibroin appears similar to tyrosine. Because cystine has a flat reflectance spectrum in the visible region from 700 to 400 nm and the powder therefore appears white, cystine absorption does not contribute to the cream colour of wool despite the high concentration of cystine residues near the cuticle surface. The disulphide absorption of solid L: -cystine in the DR spectrum at 290 nm is significantly red shifted by ~40 nm relative to its wavelength in solution, whereas homocystine and lipoic acid showed smaller red shifts of 20 nm. The large red shift observed for cystine and the large difference in intensity of absorption in its UV-visible and DR spectra may be due to differences in the dihedral angle between the crystalline solid and the solvated molecules in solution. PMID:22218994

  12. Diffuse reflectance spectroscopy of fibrous proteins.

    PubMed

    Millington, Keith R

    2012-09-01

    UV-visible diffuse reflectance (DR) spectra of the fibrous proteins wool and feather keratin, silk fibroin and bovine skin collagen are presented. Natural wool contains much higher levels of visible chromophores across the whole visible range (700-400 nm) than the other proteins and only those above 450 nm are effectively removed by bleaching. Both oxidative and reductive bleaching are inefficient for removing yellow chromophores (450-400 nm absorbers) from wool. The DR spectra of the four UV-absorbing amino acids tryptophan, tyrosine, cystine and phenylalanine were recorded as finely ground powders. In contrast to their UV-visible spectra in aqueous solution where tryptophan and tyrosine are the major UV absorbing species, surprisingly the disulphide chromophore of solid cystine has the strongest UV absorbance measured using the DR remission function F(R)(∞). The DR spectra of unpigmented feather and wool keratin appear to be dominated by cystine absorption near 290 nm, whereas silk fibroin appears similar to tyrosine. Because cystine has a flat reflectance spectrum in the visible region from 700 to 400 nm and the powder therefore appears white, cystine absorption does not contribute to the cream colour of wool despite the high concentration of cystine residues near the cuticle surface. The disulphide absorption of solid L: -cystine in the DR spectrum at 290 nm is significantly red shifted by ~40 nm relative to its wavelength in solution, whereas homocystine and lipoic acid showed smaller red shifts of 20 nm. The large red shift observed for cystine and the large difference in intensity of absorption in its UV-visible and DR spectra may be due to differences in the dihedral angle between the crystalline solid and the solvated molecules in solution.

  13. Enhancement of water retention in UV-exposed fuel-cell proton exchange membranes studied using terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Ray, Shaumik; Devi, Nirmala; Dash, Jyotirmayee; Rambabu, Gutru; Bhat, Santoshkumar D.; Pesala, Bala

    2016-02-01

    Proton Exchange Membrane (PEM) fuel cells are increasingly gaining importance as a clean energy source. PEMs need to possess high proton conductivity and should be chemically and mechanically stable in the fuel cell environment. Proton conductivity of PEM in fuel cells is directly proportional to water content in the membrane. Among the various PEMs available, Nafion has high proton conductivity even with low water content compared to SPEEK (Sulfonated Poly(ether ether ketone)) but is also expensive. SPEEK membranes and it's composites have better mechanical properties and have comparatively higher thermal stability. Operating the fuel cell at higher temperatures and at the same time maintaining the water content of the membrane is always a great challenge. In this paper, to increase water retention capacity, Nafion, SPEEK and it's composite (SPEEK PSSA-CNT) membranes are exposed to Ultra-Violet (UV) radiation for varied times. Terahertz Spectroscopy, in both pulsed and CW mode has been used as an efficient tool to quantify the water retention of the membrane. Results using Terahertz spectroscopy show that even though the initial water absorption capacity of Nafion membranes is more, SPEEK membranes and it's composites show considerable improvement in the water retention capacity upon high intensity UV irradiation.

  14. Characteristics of chiral and racemic ketoprofen drugs using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Du, Yong; Liu, Jianjun; Hong, Zhi

    2013-08-01

    Absorption spectra of chiral S-(+)- and racemic RS-ketoprofen pharmaceutical molecules in crystalline form were recorded in the terahertz region between 6 and 66 cm-1 (0.2 ~ 2.0 THz) by using time-domain terahertz spectroscopic (THz-TDS) measurement. Different distinctive absorption features were observed which are strikingly sensitive to the change of subtle conformational structures within such isostructural crystal molecules. The results suggest that the THz-TDS technique can be definitely used for distinguishing between chiral and racemic compounds in pharmaceutical and biological fields.

  15. Picosecond Transient Photoconductivity in Functionalized Pentacene Molecular Crystals Probed by Terahertz Pulse Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hegmann, F. A.; Tykwinski, R. R.; Lui, K. P.; Bullock, J. E.; Anthony, J. E.

    2002-11-01

    We have measured transient photoconductivity in functionalized pentacene molecular crystals using ultrafast optical pump-terahertz probe techniques. The single crystal samples were excited using 800nm, 100fs pulses, and the change in transmission of time-delayed, subpicosecond terahertz pulses was used to probe the photoconducting state over a temperature range from 10 to 300K. A subpicosecond rise in photoconductivity is observed, suggesting that mobile carriers are a primary photoexcitation. At times longer than 4ps, a power-law decay is observed consistent with dispersive transport.

  16. Terahertz time domain spectroscopy (THz-TDS) of hydrated biomolecular polymers and monomers

    NASA Astrophysics Data System (ADS)

    Glancy, Paul Michael

    Terahertz Time Domain Spectroscopy (THz-TDS) was utilized to obtain the complex dielectric spectra of hydrated biomolecules, betwixt the frequency range of 50 GHz to 2 THz. Two biological systems are observed; nucleic acid and carbohydrates. Monomers and polymers will be of interest for both. Utilizing both the Debye relaxation model and the suspension model, we observed both the mobility of biomolecules in solution as well as the influence they have on their surrounding water. Nucleotides and glucose (monomers) were found to have a small part in the overall dynamics of the polymers. Hydrated nucleotides were shown to form transition materials. The pyrimidine nucleotides act much like an ion where they break up the original structure of water and set up a less complicated structure (smaller main relaxation times than water) than water. Purine nucleotides act more like a hydrogen bond building material they set up a more complex hydrogen bond network (larger main relaxation times than water) than water. These nucleotides were shown to have an influence in water out to four water layers. The concentration studies that were preformed on native DNA, shows that concentration in the hydrated state is an important factor in the dielectric response. In addition, it was found that impurities in our samples did not play an important role in the dielectric response of our DNA solutions. Native DNA was shown to have a reach of six hydration layers. The influence temperature has on DNA solutions was observed, temperature has a large influence on hydrated DNA. It was found that hydrated DNA is more susceptible to change in temperature then that of bulk water. The main relaxation time increases at a much larger proportion to that of water. Using two synthetic DNA molecules with the same structure but different compositions and two carbohydrates with different structures but the same composition we found that the structure of a biopolymer is the most domination factor, rather than

  17. Apollo 17 Soil Characterization for Reflectance Spectroscopy

    NASA Technical Reports Server (NTRS)

    Taylor, L. A.; Pieters, C.; Patchen, A.; Morris, R. V.; Keller, L. P.; Wentworth, S.; McKay, D. S.

    1999-01-01

    It is the fine fractions that dominate the observed spectral signatures of bulk lunar soil, and the next to the smallest size fractions are the most similar to the overall properties of the bulk soil. Thus, our Lunar Soil Characterization Consortium has concentrated on understanding the inter-relations of compositional, mineralogical, and optical properties of the <45-micron size fraction and its component sizes (20-44 micron, 10-20 micron, and <10 micron size fractions). To be able to generalize our results beyond the particular sample set studied, it is necessary to quantitatively identify the observed effects of space weathering and evaluate the processes involved. For this, it is necessary to know the chemistry of each size fraction, modal abundances of each phase, average compositions of the minerals and glasses, I(sub s)/FeO values, reflectance spectra, and the physical makeup of the individual particles and their patinas. This characterization includes the important dissection of the pyroxene minerals into four separate populations, with data on both modes and average chemical compositions. Armed with such data, it should be possible to effectively isolate spectral effects of space weathering from spectral properties related to mineral and glass chemistry. Four mare soils from the Apollo 17 site were selected for characterization based upon similarities in bulk composition and their contrasting maturities, ranging from immature to submature to mature. The methodology of our characterization has been discussed previously. Results of the Apollo 17 mare soils, outlined herein, are being prepared for publication in MAPS. As shown, with decreasing grain size, the agglutinitic (impact) glass content profoundly increases. This is the most impressive change for the mare soils. In several soils we have examined, there is an over two-fold increase in the agglutinitic glass contents between the 90-150- micron and the 10-20-micron size fractions. Accompanying this

  18. Terahertz spectroscopy with a holographic Fourier transform spectrometer plus array detector using coherent synchrotron radiation

    SciTech Connect

    Nikolay I. Agladz, John Klopf, Gwyn Williams, Albert J. Sievers

    2010-06-01

    By use of coherent terahertz synchrotron radiation, we experimentally tested a holographic Fourier transform spectrometer coupled to an array detector to determine its viability as a spectral device. Somewhat surprisingly, the overall performance strongly depends on the absorptivity of the birefringent lithium tantalate pixels in the array detector.

  19. Terahertz Frequency-Domain Spectroscopy of Low-Pressure Acetonitrile Gas by a Photomixing Terahertz Synthesizer Referenced to Dual Optical Frequency Combs

    NASA Astrophysics Data System (ADS)

    Hsieh, Yi-Da; Kimura, Hiroto; Hayashi, Kenta; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Yasui, Takeshi

    2016-09-01

    A terahertz (THz) frequency synthesizer based on photomixing of two near-infrared lasers with a sub-THz to THz frequency offset is a powerful tool for spectroscopy of polar gas molecules due to its broad spectral coverage; however, its frequency accuracy and resolution are relatively low. To tune the output frequency continuously and widely while maintaining its traceability to a frequency standard, we developed a photomixing THz synthesizer phase-locked to dual optical frequency combs (OFCs). While the phase-locking to dual OFCs ensured continuous tuning within a spectral range of 120 GHz, in addition to the traceability to the frequency standard, use of a broadband uni-traveling carrier photodiode for photomixing enabled the generation of CW-THz radiation within a frequency range from 0.2 to 1.5 THz. We demonstrated THz frequency-domain spectroscopy of gas-phase acetonitrile CH3CN and its isotope CH3 13CN in the frequency range of 0.600-0.720 THz using this THz synthesizer. Their rotational transitions were assigned with a frequency accuracy of 8.42 × 10-8 and a frequency resolution of 520 kHz. Furthermore, the concentration of the CH3CN gas at 20 Pa was determined to be (5.41 ± 0.05) × 1014 molecules/cm3 by curve fitting analysis of the measured absorbance spectrum, and the mixture ratio of the mixed CH3CN/CH3 13CN gas was determined to be 1:2.26 with a gas concentration of 1014-1015 molecules/cm3. The developed THz synthesizer is highly promising for high-precision THz-FDS of low-pressure molecular gases and will enable the qualitative and quantitative analyses of multiple gases.

  20. Polarization orientation dependence of the far infrared spectra of oriented single crystals of 1,3,5,-trinitro-s-triazine (RDX) using terahertz-time-domain spectroscopy

    SciTech Connect

    Whitley, Von H; Hooks, Dan E; Ramos, Kyle J; O' Hara, John F; Azad, A K; Taylor, A J; Barber, J; Averitt, R D

    2008-01-01

    The far infrared spectra of (100), (010), and (001)-oriented RDX single crystals were measured as the crystal was rotated about the axis perpendicular to the polarization plane of the incident radiation. Absorption measurements were taken at temperatures of both 20 K and 295 K for all rotations using terahertz time-domain spectroscopy. A number of discrete absorptions were found ranging from 10-100 cm(-1) (0.3-3 THz). The absorptions are highly dependent on the orientation of the terahertz polarization with respect to crystallographic axes.

  1. Experimental demonstration of reflectarray antennas at terahertz frequencies.

    PubMed

    Niu, Tiaoming; Withayachumnankul, Withawat; Ung, Benjamin S-Y; Menekse, Hakan; Bhaskaran, Madhu; Sriram, Sharath; Fumeaux, Christophe

    2013-02-11

    Reflectarrays composed of resonant microstrip gold patches on a dielectric substrate are demonstrated for operation at terahertz frequencies. Based on the relation between the patch size and the reflection phase, a progressive phase distribution is implemented on the patch array to create a reflector able to deflect an incident beam towards a predefined angle off the specular direction. In order to confirm the validity of the design, a set of reflectarrays each with periodically distributed 360 × 360 patch elements are fabricated and measured. The experimental results obtained through terahertz time-domain spectroscopy (THz-TDS) show that up to nearly 80% of the incident amplitude is deflected into the desired direction at an operation frequency close to 1 THz. The radiation patterns of the reflectarray in TM and TE polarizations are also obtained at different frequencies. This work presents an attractive concept for developing components able to efficiently manipulate terahertz radiation for emerging terahertz communications.

  2. Fabrication of photonic amorphous diamonds for terahertz-wave applications

    NASA Astrophysics Data System (ADS)

    Komiyama, Yuichiro; Abe, Hiroyuki; Kamimura, Yasushi; Edagawa, Keiichi

    2016-05-01

    A recently proposed photonic bandgap material, named "photonic amorphous diamond" (PAD), was fabricated in a terahertz regime, and its terahertz-wave propagation properties were investigated. The PAD structure was fabricated from acrylic resin mixed with alumina powder, using laser lithographic, micro-additive manufacturing technique. After fabrication, the resulting structure was dewaxed and sintered. The formation of a photonic bandgap at around 0.45 THz was demonstrated by terahertz time-domain spectroscopy. Reflecting the disordered nature of the random network structure, diffusive terahertz-wave propagation was observed in the passbands; the scattering mean-free path decreased as the frequency approached the band edge. The mean-free paths evaluated at the band edges were close to the Ioffe-Regel threshold value for wave localization.

  3. Experimental demonstration of reflectarray antennas at terahertz frequencies.

    PubMed

    Niu, Tiaoming; Withayachumnankul, Withawat; Ung, Benjamin S-Y; Menekse, Hakan; Bhaskaran, Madhu; Sriram, Sharath; Fumeaux, Christophe

    2013-02-11

    Reflectarrays composed of resonant microstrip gold patches on a dielectric substrate are demonstrated for operation at terahertz frequencies. Based on the relation between the patch size and the reflection phase, a progressive phase distribution is implemented on the patch array to create a reflector able to deflect an incident beam towards a predefined angle off the specular direction. In order to confirm the validity of the design, a set of reflectarrays each with periodically distributed 360 × 360 patch elements are fabricated and measured. The experimental results obtained through terahertz time-domain spectroscopy (THz-TDS) show that up to nearly 80% of the incident amplitude is deflected into the desired direction at an operation frequency close to 1 THz. The radiation patterns of the reflectarray in TM and TE polarizations are also obtained at different frequencies. This work presents an attractive concept for developing components able to efficiently manipulate terahertz radiation for emerging terahertz communications. PMID:23481746

  4. Soil phosphorus and potassium estimation by reflectance spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Visible and near infrared (VNIR) diffuse reflectance spectroscopy has potential in site-specific measurement of soil properties. However, previous studies have reported VNIR estimates of plant available soil phosphorus (P) and potassium (K) to be of variable accuracy. In this study, we used a databa...

  5. Analytical study of spacecraft deposition contamination by internal reflection spectroscopy

    NASA Technical Reports Server (NTRS)

    Mookherji, T.

    1972-01-01

    Infrared absorption spectra of ten individual contaminant materials and four binary mixtures of these have been studied using the internal reflection spectroscopy technique. The effect of ultraviolet radiation on these contaminants has also been studied. It has been observed that all siloxanes, silanes, and esters are drastically affected by ultraviolet irradiation. In most cases polymerization and tar formation results.

  6. Instrumentation for Reflectance Spectroscopy and Microspectroscopy with Application to Astrobiology

    NASA Technical Reports Server (NTRS)

    Mouroulis, Pantazis; Blaney, Diana L.; Green, Robert O.

    2008-01-01

    We present instrument concepts for in-situ reflectance spectroscopy over a spatial resolution range from several meters to tens of micrometers. These have been adapted to the low mass and power requirements of rover or similar platforms. Described are a miniaturized imaging spectrometer for rover mast, a combined mast and arm point spectrometer, and an imaging microspectrometer for the rover arm.

  7. Estimating a soil quality index with VNIR reflectance spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sensor-based approaches to assessment and quantification of soil quality are important to facilitate cost-effective, site-specific soil management. The objective of this research was to evaluate the ability of visible, near-infrared (VNIR) diffuse reflectance spectroscopy to estimate multiple soil q...

  8. Modulation of the Hydration Water Around Monoclonal Antibodies on Addition of Excipients Detected by Terahertz Time-Domain Spectroscopy.

    PubMed

    Wallace, Vincent P; Ferachou, Denis; Ke, Peng; Day, Katie; Uddin, Shahid; Casas-Finet, Jose; Van Der Walle, Christopher F; Falconer, Robert J; Zeitler, J Axel

    2015-12-01

    Terahertz time-domain spectroscopy (THz-TDS) has been shown to detect overlapping extended hydration layers around proteins. Here, we used THz-TDS to detect modulation of the extended hydration layer around monoclonal antibodies (mAbs) by the introduction of commonly used excipients. Proline and sucrose altered the hydration layer around a mAb (mAb1), which was observed as a negative shift in the plateau in absorbance above ~100 mg/mL mAb1 (~70,000 water molecules per mAb); arginine had no effect. At lower concentrations of ~10 mg/mL mAb1 (~700,000 water molecules per mAb) proline and arginine modulated the hydration layer, which was observed as a negative shift in the relative absorbance, whereas sucrose had no effect. The changes in the extended hydration layer were not translated to shifts in the thermal stability or protein:protein interaction parameter. The hydration layer of a second mAb (mAb2) was further shown to be modulated by more complex formulations composed of two or more excipients; although the differences in terahertz absorbance were not predictive of viscosity or long-term stability. THz-TDS promises to be a useful tool for understanding a protein's interaction with excipients in solution and the challenge will be to determine how to apply this knowledge to protein formulation. PMID:26344202

  9. Modulation of the Hydration Water Around Monoclonal Antibodies on Addition of Excipients Detected by Terahertz Time-Domain Spectroscopy.

    PubMed

    Wallace, Vincent P; Ferachou, Denis; Ke, Peng; Day, Katie; Uddin, Shahid; Casas-Finet, Jose; Van Der Walle, Christopher F; Falconer, Robert J; Zeitler, J Axel

    2015-12-01

    Terahertz time-domain spectroscopy (THz-TDS) has been shown to detect overlapping extended hydration layers around proteins. Here, we used THz-TDS to detect modulation of the extended hydration layer around monoclonal antibodies (mAbs) by the introduction of commonly used excipients. Proline and sucrose altered the hydration layer around a mAb (mAb1), which was observed as a negative shift in the plateau in absorbance above ~100 mg/mL mAb1 (~70,000 water molecules per mAb); arginine had no effect. At lower concentrations of ~10 mg/mL mAb1 (~700,000 water molecules per mAb) proline and arginine modulated the hydration layer, which was observed as a negative shift in the relative absorbance, whereas sucrose had no effect. The changes in the extended hydration layer were not translated to shifts in the thermal stability or protein:protein interaction parameter. The hydration layer of a second mAb (mAb2) was further shown to be modulated by more complex formulations composed of two or more excipients; although the differences in terahertz absorbance were not predictive of viscosity or long-term stability. THz-TDS promises to be a useful tool for understanding a protein's interaction with excipients in solution and the challenge will be to determine how to apply this knowledge to protein formulation.

  10. Nondestructive evaluation of crystallized-particle size in lactose-powder by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamauchi, Satoshi; Hatakeyama, Sakura; Imai, Yoh; Tonouchi, Masayoshi

    2014-03-01

    Transmission-type terahertz time-domain spectroscopy is applied to evaluate crystallized lactose particle of size below 30 μm, which is far too small compared to the wavelength of incident terahertz (THz)-wave. The THz-absorption spectrum of lactose is successfully deconvoluted by Lorentzian to two spectra with peaks at 17.1 cm-1 (0.53 THz) and 45.6 cm-1 (1.37 THz) derived from α-lactose monohydrate, and a spectrum at 39.7 cm-1 (1.19 THz) from anhydrous β-lactose after removal of the broad-band spectrum by polynomial cubic function. Lactose is mainly crystallized into α-lactose monohydrate from the supersaturated solution at room temperature with a small amount of anhydrous β-lactose below 4%. The absorption feature is dependent on the crystallized particle size and the integrated intensity ratio of the two absorptions due to α-lactose monohydrate is correlated in linear for the size.

  11. Ultrafast terahertz spectroscopy study of Kondo insulating thin film SmB6: evidence for an emergent surface state

    NASA Astrophysics Data System (ADS)

    Zhang, Jingdi; Yong, Jie; Takeuchi, Ichiro; Greene, Richard; Averitt, Richard

    We utilize terahertz time domain spectroscopy to investigate thin films of the heavy fermion compound SmB6, a prototype Kondo insulator. Temperature dependent terahertz (THz) conductivity measurements reveal a rapid decrease in the Drude weight and carrier scattering rate at ~T* =20 K, well below the hybridization gap onset temperature (100 K). Moreover, a low-temperature conductivity plateau (below 20K) indicates the emergence of a surface state with an effective electron mass of 0.1me. Conductivity dynamics following optical excitation are also measured and interpreted using Rothwarf-Taylor (R-T) phenomenology, yielding a hybridization gap energy of 17 meV. However, R-T modeling of the conductivity dynamics reveals a deviation from the expected thermally excited quasiparticle density at temperatures below 20K, indicative of another channel opening up in the low energy electrodynamics. Taken together, these results suggest the onset of a surface state well below the crossover temperature (100K) after long-range coherence of the f-electron Kondo lattice is established. JZ and RDA acknowledge support from DOE - Basic Energy Sciences under Grant No. DE-FG02-09ER46643, under which the THz measurements and data analysis were performed. JY, IT and RLG acknowledge support from ONR N00014-13-1-0635 and NSF DMR 1410665.

  12. Strong optical reflection of rare-earth garnets in the terahertz regime by reststrahlen bands

    NASA Astrophysics Data System (ADS)

    Adachi, Masaki; Yamahara, Hiroyasu; Kawabe, Shunsuke; Matsui, Hiroaki; Tabata, Hitoshi

    2014-05-01

    The reststrahlen bands of rare-earth garnets were investigated in the terahertz regime. Through this, it was found that the crystal orientation and light polarization directly influence the reststrahlen-related dielectric absorptions of Gd3Ga5O12 (GGG), which is attributed to restriction in the vibrational motion of Gd ions. A theoretical fit to the dielectric absorption revealed that the phonon-polariton frequency in GGG crystals at around 85.5 cm-1 exhibits a narrow spectral width of 100 GHz at room temperature, as estimated using a Lorentz oscillator model. In addition, it was found that the reststrahlen bands can be readily manipulated within a range of 0.7-3.7 THz by changing the chemical composition of the garnet.

  13. Coherent broadband continuous-wave terahertz spectroscopy on solid-state samples

    NASA Astrophysics Data System (ADS)

    Roggenbuck, A.; Schmitz, H.; Deninger, A.; Cámara Mayorga, I.; Hemberger, J.; Güsten, R.; Grüninger, M.

    2010-04-01

    Measuring the complex dielectric function ɛ(ω)=ɛ1+iɛ2 of solid-state samples in the terahertz frequency range with high spectral resolution remains difficult. Using a continuous-wave terahertz spectrometer based on photomixing in the frequency range from 60 GHz to 1.8 THz, we obtain the most precise data of ɛ(ω) reported to date for the well-studied example of α-lactose monohydrate. We are able to determine both ɛ1 and ɛ2 due to coherent detection and show that the results are Kramers-Kronig consistent. Our analysis is based on scanning an interference pattern in frequency and relies on the high spectral resolution in the MHz range. This enables us to avoid mechanically moving parts such as a delay stage. Moreover, we show that the optical data can be used to determine both ɛ(ω) and the sample thickness d independently.

  14. Phase-resolved two-dimensional terahertz spectroscopy including off-resonant interactions beyond the χ(3) limit

    NASA Astrophysics Data System (ADS)

    Somma, Carmine; Folpini, Giulia; Reimann, Klaus; Woerner, Michael; Elsaesser, Thomas

    2016-05-01

    We present the first two-dimensional (2D) terahertz (THz) experiment with three phase-locked THz pulses and a fully phase-resolved detection of the nonlinearly emitted field by electrooptic sampling. In a prototype experiment we study the ultrafast dynamics of nonlinear two-phonon and two-photon interband coherences in the narrow-gap semiconductor InSb. Due to the extraordinarily large optical interband dipole of InSb the experiments were performed in the strongly nonperturbative regime of light-matter interaction allowing for impulsive off-resonant excitation of both two-phonon coherences and two-photon interband coherences, the ultrafast dynamics of which is experimentally observed as a function of the waiting time in the three-pulse 2D experiment. Our novel three-pulse 2D THz spectroscopy paves the way for the detailed investigation of nonlinear quantum coherences in solids and holds potential for an extension to other systems.

  15. New Insights into the Diverse Electronic Phases of a Novel Vanadium Dioxide Polymorph: A Terahertz Spectroscopy Study

    PubMed Central

    Lourembam, James; Srivastava, Amar; La-o-vorakiat, Chan; Rotella, H.; Venkatesan, T.; Chia, Elbert E. M.

    2015-01-01

    A remarkable feature of vanadium dioxide is that it can be synthesized in a number of polymorphs. The conductivity mechanism in the metastable layered polymorph VO2(B) thin films has been investigated by terahertz time-domain spectroscopy (THz-TDS). In VO2(B), a critical temperature of 240 K marks the appearance of a non-zero Drude term in the observed complex conductivity, indicating the evolution from a pure insulating state towards a metallic state. In contrast, the THz conductivity of the well-known VO2(M1) is well fitted only by a modification of the Drude model to include backscattering. We also identified two different THz conductivity regimes separated by temperature in these two polymorphs. The electronic phase diagram is constructed, revealing that the width and onset of the metal-insulator transition in the B phase develop differently from the M1 phase. PMID:25777320

  16. Charge transport in thin layer Na x CoO2 (x ∼ 0.63) studied by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Němec, H.; Knížek, K.; Jirák, Z.; Hejtmánek, J.; Soroka, M.; Buršík, J.

    2016-09-01

    Charge transport in Na0.63CoO2 thin film deposited by a spin-coating method was investigated experimentally by time-domain terahertz spectroscopy and theoretically using Monte Carlo calculations of charge response in nano-structured materials. The dominating type of transport mechanism over the entire investigated range of temperatures (20–300 K) is a metallic-like conductivity of charges partly confined in constituting nano-sized grains. Due to the granular character of our thin film, the scattering time at low temperatures is limited by scattering on grain boundaries and the conductivity is strongly suppressed due to capture of a major fraction of charge carriers in deep traps. Nevertheless, our experimental setup and the applied model allowed us to distinguish the parameters related to the grain interior from those influenced by grain boundaries, and to conclude that the metallic type of conductivity is the intrinsic property relevant to single crystal materials.

  17. Charge transport in thin layer Na x CoO2 (x ∼ 0.63) studied by terahertz spectroscopy.

    PubMed

    Němec, H; Knížek, K; Jirák, Z; Hejtmánek, J; Soroka, M; Buršík, J

    2016-09-01

    Charge transport in Na0.63CoO2 thin film deposited by a spin-coating method was investigated experimentally by time-domain terahertz spectroscopy and theoretically using Monte Carlo calculations of charge response in nano-structured materials. The dominating type of transport mechanism over the entire investigated range of temperatures (20-300 K) is a metallic-like conductivity of charges partly confined in constituting nano-sized grains. Due to the granular character of our thin film, the scattering time at low temperatures is limited by scattering on grain boundaries and the conductivity is strongly suppressed due to capture of a major fraction of charge carriers in deep traps. Nevertheless, our experimental setup and the applied model allowed us to distinguish the parameters related to the grain interior from those influenced by grain boundaries, and to conclude that the metallic type of conductivity is the intrinsic property relevant to single crystal materials. PMID:27365361

  18. Investigation of pharmaceutical drugs and caffeine-containing foods using Fourier and terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    KaraliÅ«nas, Mindaugas; Venckevičius, Rimvydas; Kašalynas, Irmantas; Puc, Uroš; Abina, Andreja; Jeglič, Anton; Zidanšek, Aleksander; Valušis, Gintaras

    2015-08-01

    Several pharmaceutical drugs, such as alprazolam, ibuprofen, acetaminophen, activated carbon and others, and caffeine-containing foods were tested using terahertz (THz) time domain spectroscopy in the range from 0.3 to 2 THz. The dry powder of pharmaceutical drugs was mixed with HDPE and pressed into the pellets using hydraulic press. The coffee grounds were also pressed into the pellets after ball-milling and mixing with HDPE. The caffeine containing liquid foods were dried out on the paper strips of various stacking. Experiments allow one to determine characteristic spectral signatures of the investigated substances within THz range caused by active pharmaceutical ingredients, like in the case of caffeine, as well as supporting pharmaceutical ingredients. Spectroscopic THz imaging approach is considered as a possible option to identify packaged pharmaceutical drugs. The caffeine spectral features in the tested caffeine containing foods are difficult to observed due to the low caffeine concentration and complex caffeine chemical surrounding.

  19. Improved detection sensitivity of D-mannitol crystalline phase content using differential spectral phase shift terahertz spectroscopy measurements.

    PubMed

    Allard, Jean-François; Cornet, Alain; Debacq, Christophe; Meurens, Marc; Houde, Daniel; Morris, Denis

    2011-02-28

    We report quantitative measurement of the relative proportion of δ- and β-D-mannitol crystalline phases inserted into polyethylene powder pellets, obtained by time-domain terahertz spectroscopy. Nine absorption bands have been identified from 0.2 THz to 2.2 THz. The best quantification of the δ-phase proportion is made using the 1.01 THz absorption band. Coherent detection allows using the spectral phase shift of the transmitted THz waveform to improve the detection sensitivity of the relative δ-phase proportion. We argue that differential phase shift measurements are less sensitive to samples' defects. Using a linear phase shift compensation for pellets of slightly different thicknesses, we were able to distinguish a 0.5% variation in δ-phase proportion.

  20. Nonresonant ionization of oxygen molecules by femtosecond pulses: Plasma dynamics studied by time-resolved terahertz spectroscopy

    SciTech Connect

    Mics, Zoltan; Kadlec, Filip; Kuzel, Petr; Jungwirth, Pavel; Bradforth, Stephen E.; Apkarian, V. Ara

    2005-09-08

    We show that optical pump-terahertz probe spectroscopy is a direct experimental tool for exploring laser-induced ionization and plasma formation in gases. Plasma was produced in gaseous oxygen by focused amplified femtosecond pulses. The ionization mechanisms at 400- and 800-nm excitation wavelengths differ significantly being primarily of a multiphoton character in the former case and a strong-field process in the latter case. The generation of the plasma in the focal volume of the laser and its expansion on subnanosecond time scale is directly monitored through its density-dependent susceptibility. A Drude model used to evaluate the plasma densities and electron-scattering rates successfully captures the observations for a wide range of pump intensities. In addition, rotational fingerprints of molecular and ionic species were also observed in the spectra.

  1. Glass transition dynamics of anti-inflammatory ketoprofen studied by Raman scattering and terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Shibata, Tomohiko; Igawa, Hikaru; Kim, Tae Hyun; Mori, Tatsuya; Kojima, Seiji

    2014-03-01

    A liquid-glass transition and a crystalline state of pharmaceutical racemic ketoprofen were studied by Raman scattering and the broadband terahertz time-domain spectroscopy (THz-TDS) in the frequency range from 9 to 260 cm-1. The low-frequency Raman scattering spectra clearly shows the remarkable change related to a liquid-glass transition at about Tg = 267 K. After melt-quenching at liquid nitrogen temperature, a boson peak appears at about 16.5 cm-1 near and below Tg and the intensity of quasi-elastic scattering related to structural relaxation increases markedly on heating. The crystalline racemic ketoprofen of "conformer A" shows the noncoincidence effect of mode frequencies below 200 cm-1 between Raman scattering spectra and dielectric spectra observed by THz-TDS.

  2. Terahertz polarization spectroscopy in the near-field zone of a sub-wavelength-scale metal slit.

    PubMed

    Han, Daehoon; Lee, Kanghee; Jo, Hanlae; Song, Yunheung; Kim, Minhyuk; Ahn, Jaewook

    2016-09-19

    Time-domain spectroscopy is used to probe the polarization dependence of the terahertz-frequency absorption of α-lactose molecules in the near-field vicinity of a sub-wavelength-scale metal slit. The experimental result finds that the 0.53-THz absorption of this material has an unexpected polarization dependence, strongly coupled to the slit orientation; in particular, the electric wave in parallel polarization exhibits even complete vanishing of the otherwise resonant strong absorption. The physics behind this phenomena may be explained based on the Bethe's sub-wavelength diffraction: the electric field that is measured in the far field, but diffracted from a sub-wavelength-scale metal aperture, originates from solely magnetic dipole radiation and not from the electric dipole radiation, thus showing no electrically-coupled material response. PMID:27661871

  3. [Identification of pearl powder using microscopic infrared reflectance spectroscopy].

    PubMed

    Zhang, Xuan; Hu, Chao; Yan, Yan; Yang, Hai-Feng; Li, Jun-Fang; Bai, Hua; Xi, Guang-Cheng; Liao, Jie

    2014-09-01

    Pearl is a precious ornament and traditional Chinese medicine, which application history in China is more than 2000 years. It is well known that the chemical ingredients of shell and pearl are very similar, which all of them including calcium carbonate and various amino acids. Generally, shell powders also can be used as medicine; however, its medicinal value is much lower than that of pearl powders. Due to the feature similarity between pearl powders and shell powders, the distinguishment of them by detecting chemical composition and morphology is very difficult. It should be noted that shell powders have been often posing as pearl powders in markets, which seriously infringes the interests of consumers. Identification of pearl powder was investigated by microscopic infrared reflectance spectroscopy, and pearl powder as well as shell powder was calcined at different temperatures for different time before infrared reflectance spectroscopy analysis. The experimental results indicated that when calcined at 400 °C for 30 minutes under atmospheric pressure, aragonite in pearl powder partly transformed into calcite, while aragonite in shell powder completely transformed into calcite. At the same time, the difference in phase transition between the pearl powders 'and shell powders can be easily detected by using the microscopic infrared reflectance spectroscopy. Therefore, based on the difference in their phase transition process, infrared reflectance spectroscopy can be used to identify phase transformation differences between pearl powder and shell powder. It's more meaningfully that the proposed infrared reflectance spec- troscopy method was also investigated for the applicability to other common counterfeits, such as oyster shell powders and abalone shell powders, and the results show that the method can be a simple, efficiently and accurately method for identification of pearl powder. PMID:25532338

  4. Pancreatic tissue assessment using fluorescence and reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Chandra, Malavika; Heidt, David; Simeone, Diane; McKenna, Barbara; Scheiman, James; Mycek, Mary-Ann

    2007-07-01

    The ability of multi-modal optical spectroscopy to detect signals from pancreatic tissue was demonstrated by studying human pancreatic cancer xenografts in mice and freshly excised human pancreatic tumor tissue. Measured optical spectra and fluorescence decays were correlated with tissue morphological and biochemical properties. The measured spectral features and decay times correlated well with expected pathological differences in normal, pancreatitis and adenocarcinoma tissue states. The observed differences between the fluorescence and reflectance properties of normal, pancreatitis and adenocarcinoma tissue indicate a possible application of multi-modal optical spectroscopy to differentiating between the three tissue classifications.

  5. Attenuated total reflectance spectroscopy with chirped-pulse upconversion.

    PubMed

    Shirai, Hideto; Duchesne, Constance; Furutani, Yuji; Fuji, Takao

    2014-12-01

    Chirped-pulse upconversion technique has been applied to attenuated total reflectance (ATR) infrared spectroscopy. An extremely broadband infrared pulse was sent to an ATR diamond prism and the reflected pulse was converted to the visible by using four-wave mixing in krypton gas. Absorption spectra of liquids in the range from 200 to 5500 cm(-1) were measured with a visible spectrometer on a single-shot basis. The system was applied to observe the dynamics of exchanging process of two solvents, water and acetone, which give clear vibrational spectral contrast. We observed that the exchange was finished within ∼ 10 ms. PMID:25606893

  6. Depth-resolved measurements with elliptically polarized reflectance spectroscopy

    PubMed Central

    Bailey, Maria J.; Sokolov, Konstantin

    2016-01-01

    The ability of elliptical polarized reflectance spectroscopy (EPRS) to detect spectroscopic alterations in tissue mimicking phantoms and in biological tissue in situ is demonstrated. It is shown that there is a linear relationship between light penetration depth and ellipticity. This dependence is used to demonstrate the feasibility of a depth-resolved spectroscopic imaging using EPRS. The advantages and drawbacks of EPRS in evaluation of biological tissue are analyzed and discussed. PMID:27446712

  7. Terahertz plasmonic Bessel beamformer

    SciTech Connect

    Monnai, Yasuaki; Shinoda, Hiroyuki; Jahn, David; Koch, Martin; Withayachumnankul, Withawat

    2015-01-12

    We experimentally demonstrate terahertz Bessel beamforming based on the concept of plasmonics. The proposed planar structure is made of concentric metallic grooves with a subwavelength spacing that couple to a point source to create tightly confined surface waves or spoof surface plasmon polaritons. Concentric scatterers periodically incorporated at a wavelength scale allow for launching the surface waves into free space to define a Bessel beam. The Bessel beam defined at 0.29 THz has been characterized through terahertz time-domain spectroscopy. This approach is capable of generating Bessel beams with planar structures as opposed to bulky axicon lenses and can be readily integrated with solid-state terahertz sources.

  8. Reflectance spectroscopy for noninvasive evaluation of hair follicle stage

    NASA Astrophysics Data System (ADS)

    Liu, Caihua; Guan, Yue; Wang, Jianru; Zhong, Xiewei; Liu, Xiuli; Zhu, Dan

    2015-05-01

    Hair follicle offers an excellent model for systems biology and regenerative medicine. So far, the stages of hair follicle growth have been evaluated by histological examination. In this work, a noninvasive spectroscopy was proposed by measuring the diffuse reflectance of mouse skin and analyzing the melanin value. Results show that the skin diffuse reflectance was relatively high when hair follicles were at the telogen stage and at the beginning of the anagen stage, and decreased with the progression of the anagen stage. When the hair follicle entered into the catagen stage, the diffuse reflectance gradually increased. The changes in the melanin content of skin had contrary dynamics. Substages of the hair follicle cycle could be distinguished by comparing the changes in melanin value with the histological examination. This study provided a new method for noninvasive evaluation of the hair follicle stage, and should be valuable for basic and therapeutic investigations on hair regeneration.

  9. Reflectance spectroscopy for noninvasive evaluation of hair follicle stage.

    PubMed

    Liu, Caihua; Guan, Yue; Wang, Jianru; Zhong, Xiewei; Liu, Xiuli; Zhu, Dan

    2015-05-01

    Hair follicle offers an excellent model for systems biology and regenerative medicine. So far, the stages of hair follicle growth have been evaluated by histological examination. In this work, a noninvasive spectroscopy was proposed by measuring the diffuse reflectance of mouse skin and analyzing the melanin value. Results show that the skin diffuse reflectance was relatively high when hair follicles were at the telogen stage and at the beginning of the anagen stage, and decreased with the progression of the anagen stage. When the hair follicle entered into the catagen stage, the diffuse reflectance gradually increased. The changes in the melanin content of skin had contrary dynamics. Substages of the hair follicle cycle could be distinguished by comparing the changes in melanin value with the histological examination. This study provided a new method for noninvasive evaluation of the hair follicle stage, and should be valuable for basic and therapeutic investigations on hair regeneration. PMID:25428579

  10. Determination of carrier concentration dependent electron effective mass and scattering time of n-ZnO thin film by terahertz time domain spectroscopy

    SciTech Connect

    Tang, J.; Tay, C. B.; Deng, L. Y.; Zhang, X. H.; Chai, J. W.; Qin, H.; Liu, H. W.; Venkatesan, T.; Chua, S. J.

    2014-01-21

    We demonstrated a novel and widely accessible method for determining the electron effective mass and scattering time of ZnO films with different carrier concentrations by combining terahertz time-domain spectroscopy with Hall measurement. The terahertz time domain spectroscopy (THz-TDS) transmission spectra (0.1–2THz) were well described by Drude model. It is found that electron effective mass varied from 0.23m{sub 0} to 0.26m{sub 0} as the electron concentration changes from 5.9 × 10{sup 17} cm{sup −3} to 4.0 × 10{sup 19} cm{sup −3}. The carrier concentration dependent characteristic is ascribed to the non-parabolicity of conduction band. Free carrier localization mechanism explained the discrepancy in mobilities obtained from THz-TDS and Hall measurements.

  11. Screening mail for powders using terahertz technology

    NASA Astrophysics Data System (ADS)

    Kemp, Mike

    2011-11-01

    Following the 2001 Anthrax letter attacks in the USA, there has been a continuing interest in techniques that can detect or identify so-called 'white powder' concealed in envelopes. Electromagnetic waves (wavelengths 100-500 μm) in the terahertz frequency range penetrate paper and have short enough wavelengths to provide good resolution images; some materials also have spectroscopic signatures in the terahertz region. We report on an experimental study into the use of terahertz imaging and spectroscopy for mail screening. Spectroscopic signatures of target powders were measured and, using a specially designed test rig, a number of imaging methods based on reflection, transmission and scattering were investigated. It was found that, contrary to some previous reports, bacterial spores do not appear to have any strong spectroscopic signatures which would enable them to be identified. Imaging techniques based on reflection imaging and scattering are ineffective in this application, due to the similarities in optical properties between powders of interest and paper. However, transmission imaging using time-of-flight of terahertz pulses was found to be a very simple and sensitive method of detecting small quantities (25 mg) of powder, even in quite thick envelopes. An initial feasibility study indicates that this method could be used as the basis of a practical mail screening system.

  12. Synthesis, structure, terahertz spectroscopy and luminescent properties of copper(I) complexes with mercaptan ligands and triphenylphosphine

    NASA Astrophysics Data System (ADS)

    Qiu, Qi-Ming; Liu, Min; Li, Zhong-Feng; Jin, Qiong-Hua; Huang, Xu; Zhang, Zhen-Wei; Zhang, Cun-Lin; Meng, Qing-Xuan

    2014-03-01

    The reactions of copper(I) halides with triphenylphosphine (PPh3) and mercaptan ligand [2-mercapto-6-nitrobenzothiazole (HMNBT), 2-amino-5-mercapto-1,3,4-thiadiazole (HAMTD) and 2-mercapto-5-methyl-benzimidazole (MMBD)] yielded seven complexes, [CuCl(HMNBT)(PPh3)2] (1), [CuX(HMNBT)(PPh3)]2 (X = Cl, Br) (2-3), [Cu(MNBT)(HMNBT)(PPh3)2] (4), [CuBr(HAMTD)(PPh3)2]·CH3OH (5) and [CuX(MMBD)(PPh3)2]·2CH3OH (X = Br, I) (6-7). These complexes were characterized by elemental analysis, X-ray diffraction, 1H NMR and 31P NMR spectroscopy. In these complexes the mercaptan ligands act as monodentate or bridged ligand with S as the coordination atom. In complexes 1 and 4, hydrogen bonds CH⋯X and weak interactions CH⋯π lead to the formation of chains and 2D network respectively, while complexes 2 and 3 are dinuclear. In 5-7, intramolecular hydrogen bonds link the [CuX(thione)(PPh3)2] molecules and the solvated methanol molecules into centrosymmetric dimers. Complexes 1-5 represent first copper(I) halide complexes of HMNBT and HAMTD. The complexes 1, 5, 6 and 7 exhibit interesting fluorescence in the solid state at room temperature and their terahertz (THz) time-domain spectroscopy was also studied.

  13. Terahertz spectroscopy and laser induced infrared emission spectroscopy of nitromethane and optical properties of laser-induced carriers on semiconductor surfaces probed by a 10.6 micron wavelength carbon dioxide laser

    NASA Astrophysics Data System (ADS)

    Toyoda, Yoshimasa

    This work consists of two parts, (1) Terahertz (THz) spectroscopy and laser-induced infrared emission spectroscopy of nitromethane and (2) optical properties of laser-induced carriers on semiconductor surfaces probed by a 10.6 mum wavelength CO2 laser. In the spectroscopic study of nitromethane, previously unreported low resolution rotational-torsional spectra in the THz frequency were obtained by a Bruker IFS 66 v/S Fourier transform spectrometer. The acquired spectra were then compared with a calculation based on a rotational-torsional Hamiltonian which includes centrifugal distortions and rotational-torsional coupling terms. Even though the constants used in the calculation were a result of fitting the microwave spectrum, a discrepancy was observed between the calculated and the experimentally obtained spectrum. In addition, gaseous nitromethane was irradiated with a c.w. CO 2 laser (˜20 W cm-2 intensity, 10.6 mum wavelength) and the laser-induced steady state emission spectrum was analyzed with the IFS 66 v/S spectrometer. The laser-induced emission spectrum showed the characteristics consistent with the laser-heated thermal emission. The decay constant of the emission followed by a 100 ms CO2 laser pulse was measured with a pyroelectric detector and determined to be 0.3 s. In part II, several polycrystalline semiconductors [silicon (Si), germanium (Ge), gallium arsenide (GaAs), and cadmium telluride (CdTe)] were irradiated with a 150 Ps Nd:YAG laser (532/1064 nm wavelength) and induced changes in the optical properties were monitored by measuring the time-resolved reflectance and transmittance of a low power CO2 laser incident on the samples at the Brewster angle. The experimental results showed a sub-nanosecond increase in the reflectance and a longer increase in the absorption as a result of electron-hole pairs (i.e. carriers) generated by absorption of the incident Nd:YAG laser pulses.

  14. Development of Ultrasensitive Terahertz ESR Spectroscopy for Metalloprotein Using a Microcantilever

    NASA Astrophysics Data System (ADS)

    Okamoto, Tsubasa; Takahashi, Hideyuki; Ohmichi, Eiji; Ohta, Hitoshi

    2016-09-01

    In this article, we report a novel method for ultrasensitive high-frequency electron spin resonance (HFESR) using a microcantilever. With this method, a field-gradient force exerting on a sample-holding cantilever is detected as cantilever displacement. A unique feature of this method is that a very tiny sample (~1 µg) is sufficient for HFESR measurement in the terahertz region. Thus, the application of this method to metalloprotein is expected to be of particular interest in the future. In this study, we developed two types of HFESR techniques: one for fiber-optic detection and the other for piezoresistive detection. We applied these techniques to multi-frequency HFESR measurements of metal-containing porphyrin compounds as a model metalloprotein substance and evaluated the sensitivity and feasibility of each technique.

  15. A high-sensitivity terahertz spectroscopy technology for tetracycline hydrochloride detection using metamaterials.

    PubMed

    Qin, Jianyuan; Xie, Lijuan; Ying, Yibin

    2016-11-15

    Antibiotic residues in animal-derived food due to their overuse in veterinary medicine will have potential adverse effects on human health. The rapid and accurate detection of these drugs is essential for ensuring human food safety. In particular, the current detection methods are usually limited by the low sensitivity or the tedious pre-treatment. Here we demonstrate that metamaterials operating at terahertz frequencies, acting as highly sensitive sensors, show promising potential for the detection of tetracycline hydrochloride (TCH). We were able to detect a trace amount of TCH, as small as 0.1mg/L, which was about 10(5) times enhancement compared to the measurement of TCH on a silicon substance. Our study is likely to constitute an important step toward the detection of antibiotic residues in a food matrix.

  16. Picosecond charge transport in rutile at high carrier densities studied by transient terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Zajac, V.; Němec, H.; Kužel, P.

    2016-09-01

    We study terahertz photoconductivity of a rutile single crystal between 10 and 300 K under strong photoexcitation by femtosecond pulses at 266 nm. A marked dependence of the carrier mobility on the carrier density is observed leading to highly complex transport phenomena on a picosecond time scale. We develop a general model of carrier photoconductive response in the case of time dependent inhomogeneous distribution of carrier density and mobility. This allows us to assess an important role of both electrons and holes in the response of photoexcited rutile. At low temperatures, the carrier mobility is initially reduced due to the electron-hole scattering and increases by one order of magnitude upon ambipolar diffusion of the carriers into deeper regions of the sample. At room temperature, contributions of transient hot optical phonons and/or of midinfrared polaron excitations with charge-density-dependent dielectric strength emerge in the photoconductivity spectra.

  17. Dipolar resonances in conductive carbon micro-fibers probed by near-field terahertz spectroscopy

    SciTech Connect

    Khromova, I.; Navarro-Cia, M.; Brener, I.; Reno, J. L.; Ponomarev, A.; Mitrofanov, O.

    2015-07-13

    In this study, we observe dipole resonances in thin conductive carbon micro-fibers by detecting an enhanced electric field in the near-field of a single fiber at terahertz (THz) frequencies. Time-domain analysis of the electric field shows that each fiber sustains resonant current oscillations at the frequency defined by the fiber's length. Strong dependence of the observed resonance frequency and degree of field enhancement on the fibers' conductive properties enable direct non-contact probing of the THz conductivity in single carbon micro-fibers. We find the conductivity of the fibers to be within the range of 1– 5∙104 S/m. This approach is suitable for experimental characterization of individual doped semiconductor resonators for THz metamaterials and devices.

  18. Dipolar resonances in conductive carbon micro-fibers probed by near-field terahertz spectroscopy

    DOE PAGESBeta

    Khromova, I.; Navarro-Cia, M.; Brener, I.; Reno, J. L.; Ponomarev, A.; Mitrofanov, O.

    2015-07-13

    In this study, we observe dipole resonances in thin conductive carbon micro-fibers by detecting an enhanced electric field in the near-field of a single fiber at terahertz (THz) frequencies. Time-domain analysis of the electric field shows that each fiber sustains resonant current oscillations at the frequency defined by the fiber's length. Strong dependence of the observed resonance frequency and degree of field enhancement on the fibers' conductive properties enable direct non-contact probing of the THz conductivity in single carbon micro-fibers. We find the conductivity of the fibers to be within the range of 1– 5∙104 S/m. This approach is suitablemore » for experimental characterization of individual doped semiconductor resonators for THz metamaterials and devices.« less

  19. Terahertz Spectroscopy of the Ground State of Methylamine (CH_3NH_2)

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Drouin, Brian J.

    2009-06-01

    Measurements of the torsion-rotation spectrum of methylamine have been extended into the terahertz region. The accuracy of these measurements is estimated to be ranging from 50 kHz to 100 kHz.. About 1000 lines were assigned based on a SPCAT prediction. The Hamiltonian model follows the group-theoretical formalism developed by Ohashi and Hougen. These assigned lines were fitted together with all prior available data (1800 lines) using the SPFIT program, and improved molecular parameters were obtained for CH_3NH_2 by adding the new measurements. New frequency and intensity predictions have been made based on the obtained molecular parameters. This Hamiltonian model may facilitate future studies on protonated methanol (CH_3OH_2^+). N. Ohashi and J. T.Hougen J. Mol. Spectrosco. 121, 474 (1987).

  20. Terahertz spectroscopy on Faraday and Kerr rotations in a quantum anomalous Hall state

    PubMed Central

    Okada, Ken N.; Takahashi, Youtarou; Mogi, Masataka; Yoshimi, Ryutaro; Tsukazaki, Atsushi; Takahashi, Kei S.; Ogawa, Naoki; Kawasaki, Masashi; Tokura, Yoshinori

    2016-01-01

    Electrodynamic responses from three-dimensional topological insulators are characterized by the universal magnetoelectric term constituent of the Lagrangian formalism. The quantized magnetoelectric coupling, which is generally referred to as topological magnetoelectric effect, has been predicted to induce exotic phenomena including the universal low-energy magneto-optical effects. Here we report the experimental indication of the topological magnetoelectric effect, which is exemplified by magneto-optical Faraday and Kerr rotations in the quantum anomalous Hall states of magnetic topological insulator surfaces by terahertz magneto-optics. The universal relation composed of the observed Faraday and Kerr rotation angles but not of any material parameters (for example, dielectric constant and magnetic susceptibility) well exhibits the trajectory towards the fine structure constant in the quantized limit. PMID:27436710

  1. Terahertz spectroscopy on Faraday and Kerr rotations in a quantum anomalous Hall state

    NASA Astrophysics Data System (ADS)

    Okada, Ken N.; Takahashi, Youtarou; Mogi, Masataka; Yoshimi, Ryutaro; Tsukazaki, Atsushi; Takahashi, Kei S.; Ogawa, Naoki; Kawasaki, Masashi; Tokura, Yoshinori

    2016-07-01

    Electrodynamic responses from three-dimensional topological insulators are characterized by the universal magnetoelectric term constituent of the Lagrangian formalism. The quantized magnetoelectric coupling, which is generally referred to as topological magnetoelectric effect, has been predicted to induce exotic phenomena including the universal low-energy magneto-optical effects. Here we report the experimental indication of the topological magnetoelectric effect, which is exemplified by magneto-optical Faraday and Kerr rotations in the quantum anomalous Hall states of magnetic topological insulator surfaces by terahertz magneto-optics. The universal relation composed of the observed Faraday and Kerr rotation angles but not of any material parameters (for example, dielectric constant and magnetic susceptibility) well exhibits the trajectory towards the fine structure constant in the quantized limit.

  2. Excited-state charging energies in quantum dots investigated by terahertz photocurrent spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Shibata, K.; Nagai, N.; Ndebeka-Bandou, C.; Bastard, G.; Hirakawa, K.

    2016-06-01

    We have investigated the excited-state (ES) charging energies in quantum dots (QDs) by measuring a terahertz (THz)-induced photocurrent in a single-electron transistor (SET) geometry that contains a single InAs QD between metal nanogap electrodes. A photocurrent is produced in the QD SETs through THz intersublevel transitions and the subsequent resonant tunneling. We have found that the photocurrent exhibits stepwise change even within one Coulomb blockaded region as the electrochemical potential in the QD is swept by the gate voltage. From the threshold for the photocurrent generation, we have determined the charging energies for adding an electron in the photoexcited state in the QD. Furthermore, the charging energies for the ESs with different electron configurations are clearly resolved. The present THz photocurrent measurements are essentially dynamical experiments and allow us to analyze electronic properties in off-equilibrium states in the QD.

  3. Terahertz spectroscopy on Faraday and Kerr rotations in a quantum anomalous Hall state.

    PubMed

    Okada, Ken N; Takahashi, Youtarou; Mogi, Masataka; Yoshimi, Ryutaro; Tsukazaki, Atsushi; Takahashi, Kei S; Ogawa, Naoki; Kawasaki, Masashi; Tokura, Yoshinori

    2016-01-01

    Electrodynamic responses from three-dimensional topological insulators are characterized by the universal magnetoelectric term constituent of the Lagrangian formalism. The quantized magnetoelectric coupling, which is generally referred to as topological magnetoelectric effect, has been predicted to induce exotic phenomena including the universal low-energy magneto-optical effects. Here we report the experimental indication of the topological magnetoelectric effect, which is exemplified by magneto-optical Faraday and Kerr rotations in the quantum anomalous Hall states of magnetic topological insulator surfaces by terahertz magneto-optics. The universal relation composed of the observed Faraday and Kerr rotation angles but not of any material parameters (for example, dielectric constant and magnetic susceptibility) well exhibits the trajectory towards the fine structure constant in the quantized limit. PMID:27436710

  4. Terahertz Spectroscopy of Molecules, Radicals and Ions Using Evenson-Type Tunable FIR Spectrometer

    NASA Astrophysics Data System (ADS)

    Matsushima, Fusakazu

    2012-06-01

    Frequencies of pure rotational transitions of neutral molecules, free radicals, and ionic molecules in the terahertz region have been measured precisely by using a frequency tunable far-infrared spectrometer in Toyama for more than 2 decades. The spectrometer (sometimes called as TuFIR in short) was developed by K.M. Evenson about 30 years ago. The terahertz light source is generated by synthesizing difference frequency of two mid-infrared CO_2 laser lines using a MIM diode as a photo mixer. A microwave radiation is added so that the tunable sidebands are obtained. The molecules and ions investigated up to now in Toyama are; 1) neutral molecules or radicals ( LiH, KH, 18OH, NH, N18O, NH_3), 2) molecule with internal rotation (CH_3OH including transitions between different torsional states), 3) water molecules (H_2 16O including v_2=1 excited state, H_2 17O, H_2 18O, D_2O), 4) molecular cation ( protonated rare gas atoms such as HeH^+, NeH^+, ArH^+, KrH^+, XeH^+ including their isotopic species, H_2D^+, N_2H^+, H_2F^+), 5) molecular anion (OH^-, OD^-). The following topics are picked up in the talk. 1) principle and properties of TuFIR spectrometer with its history of developments, 2) some efforts to extend the properties of the spectrometer, 3) extended negative glow discharge cell: its property and recent application to investigate molecular ions. K.M. Evenson, D.A. Jennings, and F.R. Peterson, Appl. Phys. Lett. 44, 576 (1984) I.G. Nolt et al., J. Mol. Spectrosc., 125, 274 (1987)

  5. Depth sensitive oblique polarized reflectance spectroscopy of oral epithelial tissue

    NASA Astrophysics Data System (ADS)

    Jimenez, Maria K.; Lam, Sylvia; Poh, Catherine; Sokolov, Konstantin

    2014-05-01

    Identifying depth-dependent alterations associated with epithelial cancerous lesions can be challenging in the oral cavity where variable epithelial thicknesses and troublesome keratin growths are prominent. Spectroscopic methods with enhanced depth resolution would immensely aid in isolating optical properties associated with malignant transformation. Combining multiple beveled fibers, oblique collection geometry, and polarization gating, oblique polarized reflectance spectroscopy (OPRS) achieves depth sensitive detection. We report promising results from a clinical trial of patients with oral lesions suspected of dysplasia or carcinoma demonstrating the potential of OPRS for the analysis of morphological and architectural changes in the context of multilayer, epithelial oral tissue.

  6. Analysis of remote reflection spectroscopy to monitor plant health

    NASA Astrophysics Data System (ADS)

    Woodhouse, R.; Heeb, M.; Berry, W.; Hoshizaki, T.; Wood, M.

    1994-11-01

    Remote non-contact reflection spectroscopy is examined as a method for detecting stress in Controlled Ecological Life Support System CELSS type crops. Lettuce (Latuca Sativa L. cv. Waldmans Green) and wheat (Triticum Aestivum L. cv. Yecora Rojo) were grown hydroponically. Copper and zinc treatments provided toxic conditions. Nitrogen, phosphorous, and potassium treatments were used for deficiency conditions. Water stress was also induced in test plants. Reflectance spectra were obtained in the visible and near infrared (400nm to 2600nm) wavebands. Numerous effects of stress conditions can be observed in the collected spectra and this technique appears to have promise as a remote monitor of plant health, but significant research remains to be conducted to realize the promise.

  7. Analysis of remote reflection spectroscopy to monitor plant health.

    PubMed

    Woodhouse, R; Heeb, M; Berry, W; Hoshizaki, T; Wood, M

    1994-11-01

    Remote non-contact reflection spectroscopy is examined as a method for detecting stress in Controlled Ecological Life Support System CELSS type crops. Lettuce (Lactuca [correction of Latuca] Sativa L. cv. Waldmans Green) and wheat (Triticum Aestivum L. cv. Yecora Rojo) were grown hydroponically. Copper and zinc treatments provided toxic conditions. Nitrogen, phosphorous, and potassium treatments were used for deficiency conditions. Water stress was also induced in test plants. Reflectance spectra were obtained in the visible and near infrared (400nm to 2600nm) wavebands. Numerous effects of stress conditions can be observed in the collected spectra and this technique appears to have promise as a remote monitor of plant health, but significant research remains to be conducted to realize the promise. PMID:11540181

  8. An automatic detection software for differential reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Yuksel, Seniha Esen; Dubroca, Thierry; Hummel, Rolf E.; Gader, Paul D.

    2012-06-01

    Recent terrorist attacks have sprung a need for a large scale explosive detector. Our group has developed differential reflection spectroscopy which can detect explosive residue on surfaces such as parcel, cargo and luggage. In short, broad band ultra-violet and visible light is shone onto a material (such as a parcel) moving on a conveyor belt. Upon reflection off the surface, the light intensity is recorded with a spectrograph (spectrometer in combination with a CCD camera). This reflected light intensity is then subtracted and normalized with the next data point collected, resulting in differential reflection spectra in the 200-500 nm range. Explosives show spectral finger-prints at specific wavelengths, for example, the spectrum of 2,4,6, trinitrotoluene (TNT) shows an absorption edge at 420 nm. Additionally, we have developed an automated software which detects the characteristic features of explosives. One of the biggest challenges for the algorithm is to reach a practical limit of detection. In this study, we introduce our automatic detection software which is a combination of principal component analysis and support vector machines. Finally we present the sensitivity and selectivity response of our algorithm as a function of the amount of explosive detected on a given surface.

  9. Assessing human skin with diffuse reflectance spectroscopy and colorimetry

    NASA Astrophysics Data System (ADS)

    Seo, InSeok; Liu, Yang; Bargo, Paulo R.; Kollias, Nikiforos

    2012-02-01

    Colorimetry has been used as an objective measure of perceived skin color by human eye to document and score physiological responses of the skin from external insults. CIE color space values (L*, a* and b*) are the most commonly used parameters to correlate visually perceived color attributes such as L* for pigment, a* for erythema, and b* for sallowness of the skin. In this study, we investigated the relation of Lab color scale to the amount of major skin chromophores (oxy-, deoxyhemoglobin and melanin) calculated from diffuse reflectance spectroscopy. Thirty two healthy human subjects with ages from 20 to 70 years old, skin types I-VI, were recruited for the study. DRS and colorimetry measurements were taken from the left and right cheeks, and on the right upper inner arm. The melanin content calculated from 630-700 nm range of DRS measurements was shown to correlate with the lightness of skin (L*) for most skin types. For subjects with medium-to-light complexion, melanin measured at the blue part spectrum and hemoglobin interfered on the relation of lightness of the skin color to the melanin content. The sallowness of the skin that is quantified by the melanin contribution at the blue part spectrum of DRS was found to be related to b* scale. This study demonstrates the importance of documenting skin color by assessing individual skin chromophores with diffuse reflectance spectroscopy, in comparison to colorimetry assessment.

  10. Terahertz absorption and reflection imaging of carcinoma-affected colon tissues embedded in paraffin

    NASA Astrophysics Data System (ADS)

    Wahaia, Faustino; Kasalynas, Irmantas; Venckevicius, Rimvydas; Seliuta, Dalius; Valusis, Gintaras; Urbanowicz, Andrzej; Molis, Gediminas; Carneiro, Fatima; Carvalho Silva, Catia D.; Granja, Pedro L.

    2016-03-01

    In the present study, dehydrated human colon tissues embedded in paraffin were studied at THz frequency. A compact THz imaging system with high numerical aperture optics was developed for the analysis of adenocarcinoma-affected colon sections, in transmission and reflection geometry. A comprehensive analysis of the THz images revealed a contrast up to 23% between the neoplastic and control tissues. Absorption and reflection THz images demonstrated the possibility to distinguish adenocarcinoma-affected areas even without water in the tissue, as the main contrast mechanism in THz measurements has been observed to be water absorption in in vivo or freshly excised tissues. The present results corroborate with previous histologic findings in the same tissues, and confirm that the contrast prevails even in dehydrated tissues.

  11. Double-modulation reflection-type terahertz ellipsometer for measuring the thickness of a thin paint coating.

    PubMed

    Iwata, Tetsuo; Uemura, Hiroaki; Mizutani, Yasuhiro; Yasui, Takeshi

    2014-08-25

    We constructed a double-modulation, reflection-type terahertz (THz) ellipsometer for precise measurement of the thickness of a paint film which is coated on a metal surface and which is not transparent to visible or mid-infrared light. The double-modulation technique enabled us to directly obtain two ellipsometric parameters, Δ(ω) and Ψ(ω), as a function of angular frequency, ω, with a single measurement while reducing flicker noise due to a pump laser. The bias voltage of a photoconductive antenna (PCA) used as a THz pulse emitter was modulated at 100 kHz, and a first lock-in amplifier (LA1) was connected to the output of an electro-optic (EO) signal-sampling unit. In addition, a wire-grid polarizer (WGP) was rotated at 100 Hz to conduct polarization modulation with a frequency of 200 Hz. The output signal from LA1 was fed into a second lock-in amplifier (LA2) that worked in synchronization with the rotating WGP (RWGP). By operating LA2 in a quadrature phase-detection mode, we were able to obtain in-phase and out-of-phase signals simultaneously, from which the two ellipsometric parameters for an isotropic sample could be derived at the same time while cancelling common-mode noise. The lower detection limit of the thickness measurement and the relative standard deviation (RSD) of a black paint film coated on an aluminum substrate were 4.3 µm and 1.4%, respectively. The possibility of determining all elements of the Jones matrix for an anisotropic material is also discussed.

  12. Effect of in-material losses on terahertz absorption, transmission, and reflection in photonic crystals made of polar dielectrics

    SciTech Connect

    Serebryannikov, Andriy E.; Nojima, S.; Alici, K. B.; Ozbay, Ekmel

    2015-10-07

    The effect of the material absorption factor on terahertz absorption (A), transmittance (T), and reflectance (R) for slabs of PhC that comprise rods made of GaAs, a polar dielectric, is studied. The main goal was to illustrate how critical a choice of the absorption factor for simulations is and to indicate the importance of the possible modification of the absorption ability by using either active or lossy impurities. The spectra of A, T, and R are strongly sensitive to the location of the polaritonic gap with respect to the photonic pass and stop bands connected with periodicity that enables the efficient combination of the effects of material and structural parameters. It will be shown that the spectra can strongly depend on the utilized value of the material absorption factor. In particular, both narrow and wide absorption bands may appear owing to a variation of the material parameters with a frequency in the vicinity of the polaritonic gap. The latter are often achieved at wideband suppression of transmission, so that an ultra-wide stop band can appear as a result of adjustment of the stop bands having different origin. The results obtained at simultaneous variation of the absorption factor and frequency, and angle of incidence and frequency, indicate the possibility of the existence of wide ranges of tolerance, in which the basic features do remain. This allows for mitigating the accuracy requirements for the absorption factor in simulations and promises the efficient absorption of nonmonochromatic waves and beams with a wide angular spectrum. Suppression of narrowband effects in transmission is demonstrated at rather large values of the absorption factor, when they appear due to either the defect modes related to structural defects or dispersion inspired variations of the material parameters in the vicinity of the polaritonic gap. Comparison with auxiliary structures helps one to detect the common features and differences of homogeneous slabs and slabs of a

  13. Quantification of residual crystallinity in ball milled commercially sourced lactose monohydrate by thermo-analytical techniques and terahertz spectroscopy.

    PubMed

    Smith, Geoff; Hussain, Amjad; Bukhari, Nadeem Irfan; Ermolina, Irina

    2015-05-01

    The quantification of crystallinity is necessary in order to be able to control the milling process. The use of thermal analysis for this assessment presents certain challenges, particularly in the case of crystal hydrates. In this study, the residual crystallinity on ball milling of lactose monohydrate (LMH), for periods up to 90min, was evaluated by thermo-analytical techniques (TGA, DSC) and terahertz spectroscopy (THz). In general, the results from one of the DSC analysis and the THz measurements agree showing a monotonous decrease in relative residual crystallinity with milling time (∼80% reduction after 60min milling) and a slight increase at the 90min time point. However, the estimates from TGA and two other methods of analyzing DSC curve do not agree with the former techniques and show variability with significantly higher estimates for crystallinity. It was concluded that, the thermal techniques require more complex treatment of the data in the evaluation of changes in crystallinity of a milled material (in particular to account for the de-vitrification and mutarotation of the material that inevitably occurs during the measurement cycle) while the analysis of THz data is more straightforward, with the measurement having no impact on the native state of the material. PMID:25784570

  14. Evaluation of Penicillium digitatum sterilization using non-equilibrium atmospheric pressure plasma by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Hiraoka, Takehiro; Ebizuka, Noboru; Takeda, Keigo; Ohta, Takayuki; Kondo, Hiroki; Ishikawa, Kenji; Kawase, Kodo; Ito, Masafumi; Sekine, Makoto; Hori, Masaru

    2011-10-01

    Recently, the plasma sterilization has attracted much attention as a new sterilization technique that takes the place of spraying agricultural chemicals. The conventional methods for sterilization evaluation, was demanded to culture the samples for several days after plasma treatment. Then, we focused on Terahertz time-domain spectroscopy (THz-TDS). At the THz region, vibrational modes of biological molecules and fingerprint spectra of biologically-relevant molecules were also observed. In this study, our purpose was measurement of the fingerprint spectrum of the Penicillium digitatum (PD) spore and establishment of sterilization method by THz-TDS. The sample was 40mg/ml PD spore suspensions which dropped on cover glass. The atmospheric pressure plasma generated under the conditions which Ar gas flow was 3slm, and alternating voltage of 6kV was applied. The samples were exposed the plasma from 10mm distance for 10 minutes. We could obtain the fingerprint spectrum of the PD spore from 0.5 to 0.9THz. This result indicated the possibility of in-situ evaluation for PD sterilization using THz-TDS.

  15. Transient terahertz spectroscopy of excitons and unbound carriers in quasi two-dimensional electron-hole gases

    SciTech Connect

    Kaindl, Robert A.; Hagele, D.; Carnahan, M. A.; Chemla, D. S.

    2008-09-11

    We report a comprehensive experimental study and detailed model analysis of the terahertz (THz) dielectric response and density kinetics of excitons and unbound electron-hole pairs in GaAs quantum wells. A compact expression is given, in absolute units, for the complex-valued THz dielectric function of intra-excitonic transitions between the 1s and higher-energy exciton and continuum levels. It closely describes the THz spectra of resonantly generated excitons. Exciton ionization and formation are further explored, where the THz response exhibits both intra-excitonic and Drude features. Utilizing a two-component dielectric function, we derive the underlying exciton and unbound pair densities. In the ionized state, excellent agreement is found with the Saha thermodynamic equilibrium, which provides experimental verification of the two-component analysis and density scaling. During exciton formation, in turn, the pair kinetics is quantitatively described by a Saha equilibrium that follows the carrier cooling dynamics. The THz-derived kinetics is, moreover, consistent with time-resolved luminescence measured for comparison. Our study establishes a basis for tracking pair densities via transient THz spectroscopy of photoexcited quasi-2D electron-hole gases.

  16. Electronic properties of GaAs, InAs and InP nanowires studied by terahertz spectroscopy.

    PubMed

    Joyce, Hannah J; Docherty, Callum J; Gao, Qiang; Tan, H Hoe; Jagadish, Chennupati; Lloyd-Hughes, James; Herz, Laura M; Johnston, Michael B

    2013-05-31

    We have performed a comparative study of ultrafast charge carrier dynamics in a range of III-V nanowires using optical pump-terahertz probe spectroscopy. This versatile technique allows measurement of important parameters for device applications, including carrier lifetimes, surface recombination velocities, carrier mobilities and donor doping levels. GaAs, InAs and InP nanowires of varying diameters were measured. For all samples, the electronic response was dominated by a pronounced surface plasmon mode. Of the three nanowire materials, InAs nanowires exhibited the highest electron mobilities of 6000 cm² V⁻¹ s⁻¹, which highlights their potential for high mobility applications, such as field effect transistors. InP nanowires exhibited the longest carrier lifetimes and the lowest surface recombination velocity of 170 cm s⁻¹. This very low surface recombination velocity makes InP nanowires suitable for applications where carrier lifetime is crucial, such as in photovoltaics. In contrast, the carrier lifetimes in GaAs nanowires were extremely short, of the order of picoseconds, due to the high surface recombination velocity, which was measured as 5.4 × 10⁵  cm s⁻¹. These findings will assist in the choice of nanowires for different applications, and identify the challenges in producing nanowires suitable for future electronic and optoelectronic devices.

  17. Low-frequency vibrational modes of benzoic acid investigated by terahertz time-domain spectroscopy and theoretical simulations

    NASA Astrophysics Data System (ADS)

    Yan, Hui; Fan, Wen-hui; Zheng, Zhuan-ping

    2011-08-01

    In this paper, the low-frequency vibrational modes of crystalline benzoic acid (BA) have been investigated by terahertz time-domain spectroscopy (THz-TDS) and theoretical simulations based on the linearity combination of atomic orbital within the Density Functional Theory (DFT) as well as ab initio molecular orbital method at second-order Moller-Plesset Perturbation Theory (MP2) level for single molecule and dimer. Experimentally, a series of prominent absorption features of pure benzoic acid relevant to intra- and inter-molecular vibrational modes have been obtained below 4 THz at room temperature. For the theoretical simulations, geometry-optimization results of bond lengths and dihedral angles in both BA monomer and dimer are very close to experimental neutron diffraction measurements. Furthermore, the simulation results demonstrate absorption profile centered at 1.89 THz contains low-frequency modes of Ph-COOH twisting due to intramolecular motion and cogwheel owing to intermolecular motion. All the intra- and inter-molecular vibrational modes measured have also been assigned.

  18. Study on intelligent recognition detection technology of debond defects for ceramic matrix composites based on terahertz time domain spectroscopy.

    PubMed

    Ren, Jiaojiao; Li, Lijuan; Zhang, Dandan; Qiao, Xiaoli; Lv, Qiongying; Cao, Guohua

    2016-09-10

    With the wide use of high-temperature-resistant ceramic matrix composites (CMCs) in aviation and space flight, it is important to detect the quality of the bonding. This paper used terahertz (THz) time-domain spectroscopy nondestructive testing technology to inspect the bonding defects of the CMC. This paper puts forward a method-extraction method, which is applied to make samples to simulate the bonding defect of CMC by embedding polytetrafluoroethylene (PTFE) sheets with 0.12 mm thickness into the adhesive layer and extracting it after curing and presetting the bonding defects. On the basis of the classical and analytical algorithms, such as the maximum in time-domain and power spectrum integration, through further study in the THz spectral characteristics of bonding samples for CMC, we specifically introduce the upper debond coefficient, lower debond coefficient, average absorption coefficient for the frequency domain, centroid coefficient for the frequency domain, and other characteristics. By optimizing the THz detection characteristics set, as a sample, we adopt the neural network intelligent recognition algorithm to detect the upper and lower debond defects in samples and realize the intelligent identification for CMC debond defects. PMID:27661353

  19. Testing black holes via X-ray reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Bambi, Cosimo; Nampalliwar, Sourabh; Cardenas-Avendano, Alejandro

    2016-07-01

    Astrophysical black hole candidates are thought to be the Kerr black holes of general relativity. However, a direct observational evidence is still lacking. The study of the properties of the radiation emitted by gas in the inner part of the accretion disk can provide useful information on the spacetime geometry around these compact objects and test the Kerr black hole hypothesis. The iron line method is the most promising techniques to test black hole candidates. In this talk, we present a new reflection model for testing the Kerr black hole hypothesis. We use the formalism of the transfer function and we split the calculations into two blocks. One is the calculation of the transfer function, which takes into account all the relativistic effects and only depends on the background metric. The second block is the calculation of the intrinsic spectrum in the rest frame of the gas. We have developed a code to compute transfer functions in arbitrary stationary and axisymmetric spacetimes. The transfer functions are tabulated in FITS files and combined with XILLVER, which is the best reflection code available today. The result is best model to test black hole candidates via X-ray reflection spectroscopy.

  20. Terahertz time-domain spectroscopy of two-dimensional electron gasses at high magnetic fields

    NASA Astrophysics Data System (ADS)

    Curtis, Jeremy A.

    This dissertation covers two projects that were in the logical path to studying decoherence in a high mobility GaAs two--dimensional electron gas at high magnetic fields. The first project is the ultrafast non--degenerate pump--probe spectroscopic study of bulk GaAs in the Split Florida Helix at the National High Magnetic Field Laboratory at Florida State University. This project was undertaken as a proof of concept that ultrafast optics could be done in the Split Florida Helix so that we might study a high mobility two dimensional electron gas using THz time--domain spectroscopy at high magnetic fields, which is a much more complicated measurement than the pump--probe discussed here. This demonstration was a success. We completed the first ultrafast optical study of any kind in the Florida Split Helix. We collected differential reflection data from this bulk sample that exhibited electronic and oscillatory components. These components were treated independently in the analysis by treating the electronic dynamics with a four level approximation. The electronic transition rates were extracted and agreed well with published values. This agreement is a demonstration that the spectrometer functioned as desired. The oscillatory response was found to be a result of the emission of coherent phonons upon electronic transition between the four levels. The frequency of the oscillatory response was extracted and agreed well with the theoretical value. The second project is the study of the temperature dependence of the cyclotron decay lifetimes in a Landau quantized GaAs high mobility two dimensional electron gas using THz time--domain spectroscopy at relatively low magnetic field (1.25 T). We find that the cyclotron decay lifetimes decrease monotonically with increasing temperature from 0.4 K to 100 K and that the primary pulse amplitudes increase from 0.4 K to 1.2 K, saturates above 1.2 K up to 50 K, and decreases rapidly above 50 K. We attribute this rapid drop in

  1. Quantitative determination of aflatoxin B1 concentration in acetonitrile by chemometric methods using terahertz spectroscopy.

    PubMed

    Ge, Hongyi; Jiang, Yuying; Lian, Feiyu; Zhang, Yuan; Xia, Shanhong

    2016-10-15

    Aflatoxins contaminate and colonize agricultural products, such as grain, and thereby potentially cause human liver carcinoma. Detection via conventional methods has proven to be time-consuming and complex. In this paper, the terahertz (THz) spectra of aflatoxin B1 in acetonitrile solutions with concentration ranges of 1-50μg/ml and 1-50μg/l are obtained and analyzed for the frequency range of 0.4-1.6THz. Linear and nonlinear regression models are constructed to relate the absorption spectra and the concentrations of 160 samples using the partial least squares (PLS), principal component regression (PCR), support vector machine (SVM), and PCA-SVM methods. Our results indicate that PLS and PCR models are more accurate for the concentration range of 1-50μg/ml, whereas SVM and PCA-SVM are more accurate for the concentration range of 1-50μg/l. Furthermore, ten unknown concentration samples extracted from mildewed maize are analyzed quantitatively using these methods. PMID:27173565

  2. Terahertz wave spectrum analysis of microstrip structure

    NASA Astrophysics Data System (ADS)

    Song, Mei-jing; Li, Jiu-sheng

    2011-11-01

    Terahertz wave is a kind of electromagnetic wave ranging from 0.1~10THz, between microwave and infrared, which occupies a special place in the electromagnetic spectrum. Terahertz radiation has a strong penetration for many media materials and nonpolar substance, for example, dielectric material, plastic, paper carton and cloth. In recent years, researchers around the world have paid great attention on terahertz technology, such as safety inspection, chemical biology, medical diagnosis and terahertz wave imaging, etc. Transmission properties of two-dimensional metal microstrip structures in the terahertz regime are presented and tested. Resonant terahertz transmission was demonstrated in four different arrays of subwavelength microstrip structure patterned on semiconductor. The effects of microstrip microstrip structure shape were investigated by using terahertz time-domain spectroscopy system. The resonant terahertz transmission has center frequency of 2.05 THz, transmission of 70%.

  3. Terahertz wave spectrum analysis of microstrip structure

    NASA Astrophysics Data System (ADS)

    Song, Mei-jing; Li, Jiu-sheng

    2012-03-01

    Terahertz wave is a kind of electromagnetic wave ranging from 0.1~10THz, between microwave and infrared, which occupies a special place in the electromagnetic spectrum. Terahertz radiation has a strong penetration for many media materials and nonpolar substance, for example, dielectric material, plastic, paper carton and cloth. In recent years, researchers around the world have paid great attention on terahertz technology, such as safety inspection, chemical biology, medical diagnosis and terahertz wave imaging, etc. Transmission properties of two-dimensional metal microstrip structures in the terahertz regime are presented and tested. Resonant terahertz transmission was demonstrated in four different arrays of subwavelength microstrip structure patterned on semiconductor. The effects of microstrip microstrip structure shape were investigated by using terahertz time-domain spectroscopy system. The resonant terahertz transmission has center frequency of 2.05 THz, transmission of 70%.

  4. Time-resolved terahertz spectroscopy of electrically conductive metal-organic frameworks doped with redox active species

    NASA Astrophysics Data System (ADS)

    Alberding, Brian G.; Heilweil, Edwin J.

    2015-09-01

    Metal-Organic Frameworks (MOFs) are three-dimensional coordination polymers that are well known for large pore surface area and their ability to adsorb molecules from both the gaseous and solution phases. In general, MOFs are electrically insulating, but promising opportunities for tuning the electronic structure exist because MOFs possess synthetic versatility; the metal and organic ligand subunits can be exchanged or dopant molecules can be introduced into the pore space. Two such MOFs with demonstrated electrical conductivity are Cu3(1,3,5-benzenetricarboxylate)2, a.k.a HKUST-1, and Cu[Ni(pyrazine-2,3-dithiolate)2]. Herein, these two MOFs have been infiltrated with the redox active species 7,7,8,8-tetracyanoquinodimethane (TCNQ) and iodine under solution phase conditions and shown to produce redox products within the MOF pore space. Vibrational bands assignable to TCNQ anion and triiodide anion have been observed in the Mid-IR and Terahertz ranges using FTIR Spectroscopy. The MOF samples have been further investigated by Time-Resolved Terehertz Spectroscopy (TRTS). Using this technique, the charge mobility, separation, and recombination dynamics have been followed on the picosecond time scale following photoexcitation with visible radiation. The preliminary results show that the MOF samples have small inherent photoconductivity with charge separation lifetimes on the order of a few picoseconds. In the case of HKUST-1, the MOF can also be supported by a TiO2 film and initial results show that charge injection into the TiO2 layer occurs with a comparable efficiency to the dye sensitizer N3, [cis-Bis(isothiocyanato)-bis(2,2'-bipyridyl-4,4'-dicarboxylato ruthenium(II)], and therefore this MOF has potential as a new light absorbing and charge conducting material in photovoltaic devices.

  5. Analysis of silage composition by near-infrared reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Reeves, James B., III; Blosser, Timothy H.; Colenbrander, V. F.

    1991-02-01

    Two studies were performed to investigate the feasibility of using near infrared reflectance spectroscopy (NIRS) with undried silages. In the first study silages were analyzed for major components (e. g. dry matter crude protein and other forms of nitrogen fiber and in vitro digestible dry matter) and short chain fatty acids (SCFA). NIRS was found to operate satisfactorily except for some forms of nitrogen and SCFA. In study two various methods of grinding spectral regions and sample presentation were examined. Undried Wiley ground samples in a rectangular cell gave the best overall results for non-dry ice undried grinds with wavelengths between 1100 and 2498 nm. Silages scanned after drying however produced the best results. Intact samples did not perform as well as ground samples and wavelengths below 1100 nm were of little use. 2 .

  6. Reflectance difference spectroscopy of water on Cu(110)

    NASA Astrophysics Data System (ADS)

    Denk, M.; Hohage, M.; Sun, L. D.; Zeppenfeld, P.; Esser, N.; Cobet, C.

    2014-09-01

    The adsorption of H2O on Cu(110) was probed by means of reflectance difference spectroscopy (RDS) in the energy range between 1.5 and 9.3 eV and by scanning tunneling microscopy (STM). The adsorption of water on the pristine Cu(110) substrate mainly induces changes in the Cu surface state related optical transitions. Furthermore, the H2O adsorbate modifies the Cu bulk transitions. In particular, our investigations demonstrate that the coverage-dependent phase transition from 1D pentamer chains to a (7 × 8) superstructure can be monitored by means of RDS. In the vacuum-UV range, new RD features assigned to Cu bulk transitions were detected. Adsorption on the metal surface strongly modifies or quenches the H2O HOMO-LUMO transition, whereby a distinct RD feature of the water molecules themselves in the vacuum-UV range is absent.

  7. Multispectral terahertz sensing with highly flexible ultrathin metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Yahiaoui, Riad; Tan, Siyu; Cong, Longqing; Singh, Ranjan; Yan, Fengping; Zhang, Weili

    2015-08-01

    We report the simulation, fabrication, and experimental characterization of a multichannel metamaterial absorber with the aim to be used as a label-free sensing platform in the terahertz regime. The topology of the investigated resonators deposited on a thin flexible polymer by means of optical lithography is capable of supporting multiple resonances over a broad frequency range due to the individual contribution of each sub-element of the unit cell. In order to explore the performance of the chosen structure in terms of sensing phenomenon, the reflection feature is monitored upon variation of the refractive index and the thickness of the analyte. We achieve numerically maximum frequency sensitivity of about 139.2 GHz/refractive index unit. Measurements carried out using terahertz time-domain spectroscopy show good agreement with the numerical predictions. The results are very promising, suggesting a potential use of the metamaterial absorber in wide variety of multispectral terahertz sensing applications.

  8. 3D measurements of live cells via digital holographic microscopy and terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Park, Jun Yong; Oser, Dorian; Iapozzuto, Peter; Norbury, Sean; Mahajan, Supriya; Khmaladze, Alexander; Sharikova, Anna

    2016-03-01

    This is a study of the central nervous system (CNS) cells, including brain micro vascular endothelial cells (BMV) that constitute the blood brain barrier, and C6 glial cells that are the predominant cell in the brain. The cells are exposed to various chemicals by non-invasive, label-free methods. Digital holographic microscopy (DHM) is a technique that records an interference pattern between an object and reference waves, so that the computationally reconstructed holographic image contains both amplitude and phase information, and 3D images are obtained. The measurement of cell cultures by digital holographic microscopy yields information about cell death mechanisms, since these processes are correlated with individual cell volume. Our in-house DHM combines a visible (red) laser source with a conventional microscope base, and LabVIEW-run data processing. Terahertz spectral signatures are associated with structural changes in molecules and provide complementary information about cells. Both CNS cells BMV and C6 cells are treated with the drug "Methamphetamine" (METH), which induces apoptosis in neuronal cells and exhibits decrease in cell volume, a characteristic of cells undergoing apoptosis (induced cell death). METH can cause CNS cell death by cross-talk between mitochondria-, endoplasmic reticulum-, and receptor-mediated apoptotic events, all of which results in drug induced changes in neuroplasticity and significant neuropathology. Doxorubicin (DOX), a popular anticancer drug, is used as a control. We observe that METH treatment resulted in more pronounced cell volume shrinkage in both the BMV and C6 cells, as compared to DOX-induced cell apoptosis.

  9. Hydration and hydrogen bond network of water around hydrophobic surface investigated by terahertz spectroscopy.

    PubMed

    Shiraga, K; Suzuki, T; Kondo, N; Ogawa, Y

    2014-12-21

    Water conformation around hydrophobic side chains of four amino acids (glycine, L-alanine, L-aminobutyric acid, and L-norvaline) was investigated via changes in complex dielectric constant in the terahertz (THz) region. Each of these amino acids has the same hydrophilic backbone, with successive additions of hydrophobic straight methylene groups (-CH2-) to the side chain. Changes in the degree of hydration (number of dynamically retarded water molecules relative to bulk water) and the structural conformation of the water hydrogen bond (HB) network related to the number of methylene groups were quantitatively measured. Since dielectric responses in the THz region represent water relaxations and water HB vibrations at a sub-picosecond and picosecond timescale, these measurements characterized the water relaxations and HB vibrations perturbed by the methylene apolar groups. We found each successive straight -CH2- group on the side chain restrained approximately two hydrophobic hydration water molecules. Additionally, the number of non-hydrogen-bonded (NHB) water molecules increased slightly around these hydrophobic side chains. The latter result seems to contradict the iceberg model proposed by Frank and Evans, where water molecules are said to be more ordered around apolar surfaces. Furthermore, we compared the water-hydrophilic interactions of the hydrophilic amino acid backbone with those with the water-hydrophobic interactions around the side chains. As the hydrophobicity of the side chain increased, the ordering of the surrounding water HB network was altered from that surrounding the hydrophilic amino acid backbone, thereby diminishing the fraction of NHB water and ordering the surrounding tetrahedral water HB network.

  10. Hydration and hydrogen bond network of water around hydrophobic surface investigated by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Shiraga, K.; Suzuki, T.; Kondo, N.; Ogawa, Y.

    2014-12-01

    Water conformation around hydrophobic side chains of four amino acids (glycine, L-alanine, L-aminobutyric acid, and L-norvaline) was investigated via changes in complex dielectric constant in the terahertz (THz) region. Each of these amino acids has the same hydrophilic backbone, with successive additions of hydrophobic straight methylene groups (-CH2-) to the side chain. Changes in the degree of hydration (number of dynamically retarded water molecules relative to bulk water) and the structural conformation of the water hydrogen bond (HB) network related to the number of methylene groups were quantitatively measured. Since dielectric responses in the THz region represent water relaxations and water HB vibrations at a sub-picosecond and picosecond timescale, these measurements characterized the water relaxations and HB vibrations perturbed by the methylene apolar groups. We found each successive straight -CH2- group on the side chain restrained approximately two hydrophobic hydration water molecules. Additionally, the number of non-hydrogen-bonded (NHB) water molecules increased slightly around these hydrophobic side chains. The latter result seems to contradict the iceberg model proposed by Frank and Evans, where water molecules are said to be more ordered around apolar surfaces. Furthermore, we compared the water-hydrophilic interactions of the hydrophilic amino acid backbone with those with the water-hydrophobic interactions around the side chains. As the hydrophobicity of the side chain increased, the ordering of the surrounding water HB network was altered from that surrounding the hydrophilic amino acid backbone, thereby diminishing the fraction of NHB water and ordering the surrounding tetrahedral water HB network.

  11. Nanoscale Andreev Reflection Spectroscopy on Bismuth-Chalcogenide Topological Insulators

    NASA Astrophysics Data System (ADS)

    Granstrom, C. R.; Fridman, I.; Liang, R. X.; Lei, H.; Petrovic, C.; Yang, Shuo; Wu, K. H.; Wei, J. Y. T.

    Andreev reflection (AR) is the basic mechanism underlying the superconducting proximity effect which, at the interface between a topological insulator (TI) and a spin-singlet superconductor, can induce chiral p-wave pairing in the TI. Despite this novel importance, it is not well understood how AR is affected by the unique attributes of a three-dimensional TI, namely the Dirac dispersion and helical spin-polarization of its surface states. In this work, we use both s-wave and d-wave superconducting tips to perform AR spectroscopy at 4.2 K on flux-grown Bi2Se3 and Bi2Te3 single crystals, as well as epitaxial Bi2Se3 thin films grown on SrTiO3 substrates by molecular beam epitaxy. These AR measurements are complemented by scanning tunneling spectroscopy, in order to characterize the superconducting tip as well as the doping level and surface condition of the TI sample. Our data are analyzed using BTK theory, in light of the characteristic band structure of bismuth chalcogenides, to elucidate how the band structure affects the AR process. Work supported by: NSERC, CFI-OIT, the Canadian Institute for Advanced Research, and the Department of Energy.

  12. Phase-Sensitive Reflective Imaging Device in the mm-wave and Terahertz Regions

    NASA Astrophysics Data System (ADS)

    Gallerano, Gian Piero; Doria, Andrea; Germini, Marzia; Giovenale, Emilio; Messina, Giovanni; Spassovsky, Ivan P.

    2009-12-01

    Two Free Electron Laser sources have been developed at ENEA-Frascati for a variety of applications: A Compact Free Electron Laser (C-FEL) that provides coherent radiation in the frequency range between 90 and 150 GHz Gallerano et al. (Infrared Phys. and Techn. 40:161, 1999), and a second source, FEL-CATS, which utilizes a peculiar radio-frequency structure to generate coherent emission in the range 0.4 to 0.7 THz Doria et al. (Phys. Rev. Lett 93:264801, 2004). The high peak power of several kW in 15 to 50 ps pulses, makes these sources particularly suitable for the assessment of exposure limits in biological systems and for long range detection. In this paper we present a phase-sensitive reflective imaging device in the mm-wave and THz regions, which has proven to be a valuable tool in the biological Ramundo-Orlando et al. (Bioelectromagnetics 28:587-598, 2007), environmental Doria et al. (2005) and art conservation fields Gallerano et al. (2008). Different setups have been tested at different levels of spatial resolution to image objects from a few centimeter square to larger sizes. Images have been compared to identify and characterize the contrast mechanism.

  13. Resonant Reflection Spectroscopy of Biomolecular Arrays in Muscle

    PubMed Central

    Young, Kevin W.; Radic, Stojan; Myslivets, Evgeny; O’Connor, Shawn M.; Lieber, Richard L.

    2014-01-01

    Sarcomeres, the functional units of contraction in striated muscle, are composed of an array of interdigitating protein filaments. Direct interaction between overlapping filaments generates muscular force, which produces animal movement. When filament length is known, sarcomere length successfully predicts potential force, even in whole muscles that contain billions of sarcomere units. Inability to perform in vivo sarcomere measurements with submicrometer resolution is a long-standing challenge in the muscle physiology field and has hampered studies of normal muscle function, adaptation, injury, aging, and disease, particularly in humans. Here, we develop theory and demonstrate the feasibility of to our knowledge a new technique that measures sarcomere length with submicrometer resolution. In this believed novel approach, we examine sarcomere structure by measuring the multiple resonant reflections that are uniquely defined by Fourier decomposition of the sarcomere protein spatial framework. Using a new supercontinuum spectroscopic system, we show close agreement between sarcomere lengths measured by resonant reflection spectroscopy and laser diffraction in an ensemble of 10 distinct muscles. PMID:25418304

  14. Reduction of effective terahertz focal spot size by means of nested concentric parabolic reflectors

    SciTech Connect

    Neumann, V. A.; Laurita, N. J.; Pan, LiDong; Armitage, N. P.

    2015-09-15

    An ongoing limitation of terahertz spectroscopy is that the technique is generally limited to the study of relatively large samples of order 4 mm across due to the generally large size of the focal beam spot. We present a nested concentric parabolic reflector design which can reduce the terahertz focal spot size. This parabolic reflector design takes advantage of the feature that reflected rays experience a relative time delay which is the same for all paths. The increase in effective optical path for reflected light is equivalent to the aperture diameter itself. We have shown that the light throughput of an aperture of 2 mm can be increased by a factor 15 as compared to a regular aperture of the same size at low frequencies. This technique can potentially be used to reduce the focal spot size in terahertz spectroscopy and enable the study of smaller samples.

  15. Probing hydrogen-bonding in binary liquid mixtures with terahertz time-domain spectroscopy: a comparison of Debye and absorption analysis.

    PubMed

    Tan, Nicholas Y; Li, Ruoyu; Bräuer, Pierre; D'Agostino, Carmine; Gladden, Lynn F; Zeitler, J Axel

    2015-02-28

    Terahertz time-domain spectroscopy is used to explore hydrogen bonding structure and dynamics in binary liquid mixtures, spanning a range of protic-protic, protic-aprotic and aprotic-aprotic systems. A direct absorption coefficient analysis is compared against more complex Debye analysis and we observed good agreement of the two methods in determining the hydrogen bonding properties when at least one of the mixture components is protic. When both components are aprotic, we show that the trend in absorption coefficients match well with the theoretical trend in strength of hydrogen bond interactions predicted based on steric and electronic properties of the components.

  16. Early detection of skin cancer via terahertz spectral profiling and 3D imaging.

    PubMed

    Rahman, Anis; Rahman, Aunik K; Rao, Babar

    2016-08-15

    Terahertz scanning reflectometry, terahertz 3D imaging and terahertz time-domain spectroscopy have been used to identify features in human skin biopsy samples diagnosed for basal cell carcinoma (BCC) and compared with healthy skin samples. It was found from the 3D images that the healthy skin samples exhibit regular cellular pattern while the BCC skin samples indicate lack of regular cell pattern. The skin is a highly layered structure organ; this is evident from the thickness profile via a scan through the thickness of the healthy skin samples, where, the reflected intensity of the terahertz beam exhibits fluctuations originating from different skin layers. Compared to the healthy skin samples, the BCC samples' profiles exhibit significantly diminished layer definition; thus indicating a lack of cellular order. In addition, terahertz time-domain spectroscopy reveals significant and quantifiable differences between the healthy and BCC skin samples. Thus, a combination of three different terahertz techniques constitutes a conclusive route for detecting the BCC condition on a cellular level compared to the healthy skin. PMID:27040943

  17. Terahertz metamaterials

    SciTech Connect

    Chen, Hou-tong; Taylor, Antoineete J; Azad, Abul K; O' Hara, John F

    2009-01-01

    In this paper we present our recent developments in terahertz (THz) metamaterials and devices. Planar THz metamaterials and their complementary structures fabricated on suitable substrates have shown electric resonant response, which causes the band-pass or band-stop property in THz transmission and reflection. The operational frequency can be further tuned up to 20% upon photoexcitation of an integrated semiconductor region in the splitring resonators as the metamaterial elements. On the other hand, the use of semiconductors as metamaterial substrates enables dynamical control of metamaterial resonances through photoexcitation, and reducing the substrate carrier lifetime further enables an ultrafast switching recovery. The metamaterial resonances can also be actively controlled by application of a voltage bias when they are fabricated on semiconductor substrates with appropriate doping concentration and thickness. Using this electrically driven approach, THz modulation depth up to 80% and modulation speed of 2 MHz at room temperature have been demonstrated, which suggests practical THz applications.

  18. Probing skin interaction with hydrogen peroxide using diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zonios, George; Dimou, Aikaterini; Galaris, Dimitrios

    2008-01-01

    Hydrogen peroxide is an important oxidizing agent in biological systems. In dermatology, it is frequently used as topical antiseptic, it has a haemostatic function, it can cause skin blanching, and it can facilitate skin tanning. In this work, we investigated skin interaction with hydrogen peroxide, non-invasively, using diffuse reflectance spectroscopy. We observed transient changes in the oxyhaemoglobin and deoxyhaemoglobin concentrations as a result of topical application of dilute H2O2 solutions to the skin, with changes in deoxyhaemoglobin concentration being more pronounced. Furthermore, we did not observe any appreciable changes in melanin absorption properties as well as in the skin scattering properties. We also found no evidence for production of oxidized haemoglobin forms. Our observations are consistent with an at least partial decomposition of hydrogen peroxide within the stratum corneum and epidermis, with the resulting oxygen and/or remaining hydrogen peroxide inducing vasoconstriction to dermal blood vessels and increasing haemoglobin oxygen saturation. An assessment of the effects of topical application of hydrogen peroxide to the skin may serve as the basis for the development of non-invasive techniques to measure skin antioxidant capacity and also may shed light onto skin related disorders such as vitiligo.

  19. Noninvasive measurements of carotenoids in bovine udder by reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Klein, Julia; Darvin, Maxim E.; Müller, Kerstin E.; Lademann, Jürgen

    2012-10-01

    For a long time, the antioxidative status in cattle has been discussed as an indicator for stress conditions resulting from disease or exertion. Until now, invasive approaches have been necessary to obtain blood samples or biopsy materials and gain insights into the antioxidative status of cattle. Due to these efforts and the costs of the analyses, serial sampling is feasible in an experimental setting, but not for measurements on a routine basis. The present study focuses on the feasibility of an innovative, noninvasive spectroscopic technique that allows in vivo measurements of carotenoids in the skin by reflection spectroscopy. To this end, in a first trial, repeated measurements of the carotenoid concentration of the udder skin were performed on 25 healthy cattle from different breeds. Carotenoid concentrations showed highly significant differences between individual animals (P<0.001), although they were kept under the same environmental conditions and received the same diet. The carotenoid concentrations in "sensitive" and "robust" cows (evaluated by a temperament test) differed significantly (P<0.005), with higher concentrations observed in robust cows.

  20. Aerosol collection and analysis using diffuse reflectance infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Samuels, Alan C.; Wong, Diane M.; Meyer, Gerald J.; Roelant, Geoffrey J.; Williams, Barry R.; Miles, Ronald W., Jr.; Manning, Christopher J.

    2004-08-01

    Infrared spectroscopy is routinely employed for the identification of organic molecules and, more recently, for the classification of biological materials. We have developed a sample collection method that facilitates infrared analysis of airborne particulates using a diffuse reflectance (DR) technique. Efforts are underway to extend the method to include simultaneous analysis of vapor phase organics by using adsorbent substrates compatible with the DR technique. This series of laboratory results provides proof-of-principle for both the sample collection and data collection processes. Signal processing of the DR spectra is shown to provide rapid qualitative identification of representative aerosol materials, including particulate matter commonly found in the environment. We compare the results for such materials as bacterial spores, pollens and molds, clays and dusts, smoke and soot. Background correction analysis is shown to be useful for differentiation and identification of these constituents. Issues relating to complex mixtures of environmental samples under highly variable conditions are considered. Instrumentation development and materials research are now underway with the aim of constructing a compact sampling system for near real-time monitoring of aerosol and organic pollutants. A miniature, tilt-compensated Fourier transform spectrometer will provide spectroscopic interrogation. A series of advanced digital signal processing methods are also under development to enhance the sensor package. The approach will be useful for industrial applications, chemical and biological agent detection, and environmental monitoring for chemical vapors, hazardous air pollutants, and allergens.

  1. Intramyocardial oxygen transport by quantitative diffuse reflectance spectroscopy in calves

    NASA Astrophysics Data System (ADS)

    Lindbergh, Tobias; Larsson, Marcus; Szabó, Zoltán; Casimir-Ahn, Henrik; Strömberg, Tomas

    2010-03-01

    Intramyocardial oxygen transport was assessed during open-chest surgery in calves by diffuse reflectance spectroscopy using a small intramuscular fiber-optic probe. The sum of hemo- and myoglobin tissue fraction and oxygen saturation, the tissue fraction and oxidation of cytochrome aa3, and the tissue fraction of methemoglobin were estimated using a calibrated empirical light transport model. Increasing the oxygen content in the inhaled gas, 21%-50%-100%, in five calves (group A) gave an increasing oxygen saturation of 19+/-4%, 24+/-5%, and 28+/-8% (p<0.001, ANOVA repeated measures design) and mean tissue fractions of 1.6% (cytochrome aa3) and 1.1% (hemo- and myoglobin). Cardiac arrest in two calves gave an oxygen saturation lower than 5%. In two calves (group B), a left ventricular assistive device (LVAD pump) was implanted. Oxygen saturation in group B animals increased with LVAD pump speed (p<0.001, ANOVA) and with oxygen content in inhaled gas (p<0.001, ANOVA). The cytochrome aa3 oxidation level was above 96% in both group A and group B calves, including the two cases involving cardiac arrest. In conclusion, the estimated tissue fractions and oxygenation/oxidation levels of the myocardial chromophores during respiratory and hemodynamic provocations were in agreement with previously presented results, demonstrating the potential of the method.

  2. Direct MD Simulations of Terahertz Absorption and 2D Spectroscopy Applied to Explosive Crystals.

    PubMed

    Katz, G; Zybin, S; Goddard, W A; Zeiri, Y; Kosloff, R

    2014-03-01

    A direct molecular dynamics simulation of the THz spectrum of a molecular crystal is presented. A time-dependent electric field is added to a molecular dynamics simulation of a crystal slab. The absorption spectrum is composed from the energy dissipated calculated from a series of applied pulses characterized by a carrier frequency. The spectrum of crystalline cyclotrimethylenetrinitramine (RDX) and triacetone triperoxide (TATP) were simulated with the ReaxFF force field. The proposed direct method avoids the linear response and harmonic approximations. A multidimensional extension of the spectroscopy is suggested and simulated based on the nonlinear response to a single polarized pulse of radiation in the perpendicular polarization direction. PMID:26274066

  3. Terahertz waves emitted from an optical fiber.

    PubMed

    Yi, Minwoo; Lee, Kanghee; Lim, Jongseok; Hong, Youngbin; Jho, Young-Dahl; Ahn, Jaewook

    2010-06-21

    We report a simple method of creating terahertz waves by applying the photo-Dember effect in a (100)-oriented InAs film coated onto the 45-degree wedged-end facet of an optical fiber. The terahertz waves are generated by infrared pulses guided through the optical fiber which is nearly in contact with a sample and then measured by a conventional photo-conductive antenna detector. Using this alignment-free terahertz source, we performed proof-of-principle experiments of terahertz time-domain spectroscopy and near-field terahertz microscopy. We obtained a bandwidth of 2 THz and 180-microm spatial resolution. Using this method, the THz imaging resolution is expected to be reduced to the size of the optical fiber core. Applications of this device can be extended to sub-wavelength terahertz spectroscopic imaging, miniaturized terahertz system design, and remote sensing.

  4. Asymmetric planar terahertz metamaterials

    SciTech Connect

    Singh, Ramjan; Al - Naib, Ibraheem A. I.; Koch, Martin; Zhang, Weili

    2010-01-01

    Using terahertz time-domain spectroscopy, we report an experimental observation of three distinct resonances in split ring resonators (SRRs) for both vertical and horizontal electric field polarizations at normal incidence. Breaking the symmetry in SRRs by gradually displacing the capacitive gap from the centre towards the comer of the ring allows for an 85% modulation of the fundamental inductive-capacitive (LC) resonance. Increasing asymmetry leads to the evolution of an otherwise inaccessible high quality factor electric quadrupole resonance that can be exploited for bio-sensing applications in the terahertz region.

  5. Terahertz Spectroscopy of Molecules in the Interstellar Medium and around Stars - Sure Bets and Challenges

    NASA Astrophysics Data System (ADS)

    Menten, Karl M.

    2009-06-01

    In the very near future, powerful new observatories willrevolutionize broad band astronomical spectroscopy at THz frequencies. These include the Herschel Space Observatory, the Atacama Large Millimeter Array and, at somewhat lower, GHz, frequencies the Expanded Very Large Array. The latter two, ``radio''-style interferometers will allow sub-arcsecond, high spectral resolution imaging with total instantaneous observing bandwidths up to 100 times larger than present day facilities. This will allow comprehensive multi-transition/multi species studies that offer new approaches to a variety of astrophysical/chemical areas all of which are dependent on the availability of extensive laboratory data. To give a few examples: For many interesting sources it will be possible to get a complete astrochemical ``fingerprint'' in a single observing session with high-quality images of the distributions of the individual species! Targets include the extremely molecule-rich hot molecular cores around protostellar objects and emission from vibrationally excited lines from the innermost circumstellar envelopes of nearby asymptotic branch branch stars which will be imaged with a resolution better than the stellar diameter. Complete, high spectral resolution scans of various keystone objects over the whole 480-1250 and 1410-1920 GHz ranges will be conducted by the Heterodyne Instrument for the Far-Infrared (HIFI) aboard Herschel. These include lines from various important hydride species and, importantly, water vapor that are not observable from the ground. Organic molecules have hundreds of GHz/THz lines. However, due to the generally low abundances and large partition functions of ``new'' (yet to identified) very complex species, all of these are weak and have to be picked out of a thicket of also weak rotational lines from within relatively low energy vibrationally excited levels from various isotopologues of known species. Here, comprehensive model spectra of all the species known to

  6. Applications of Terahertz Time-Domain Reflectometry

    NASA Astrophysics Data System (ADS)

    Kitahara, Hideaki; Takano, Keisuke; Ikeda, Takeshi; Tani, Masahiko; Hangyo, Masanori

    A reflection-type terahertz (THz) time-domain spectroscopy (TDS) is applied to non-contact and non-destructive diagnosis of the surface and inner-structure of test samples. Raster scan imaging and THz optical coherence tomography (THz-OCT) are demonstrated for a bank bill, a high voltage cable and an indented impression on a memo-pad paper. The watermark of the bank bill, the indented impression, and a flaw in the cable are detected successfully. These results indicate that THz imaging is potentially useful for the analysis of surfaces and inner-structures of products made with various materials.

  7. Preferential solvation of lysozyme in dimethyl sulfoxide/water binary mixture probed by terahertz spectroscopy.

    PubMed

    Das, Dipak Kumar; Patra, Animesh; Mitra, Rajib Kumar

    2016-09-01

    We report the changes in the hydration dynamics around a model protein hen egg white lysozyme (HEWL) in water-dimethyl sulfoxide (DMSO) binary mixture using THz time domain spectroscopy (TTDS) technique. DMSO molecules get preferentially solvated at the protein surface, as indicated by circular dichroism (CD) and Fourier transform infrared (FTIR) study in the mid-infrared region, resulting in a conformational change in the protein, which consequently modifies the associated hydration dynamics. As a control we also study the collective hydration dynamics of water-DMSO binary mixture and it is found that it follows a non-ideal behavior owing to the formation of DMSO-water clusters. It is observed that the cooperative dynamics of water at the protein surface does follow the DMSO-mediated conformational modulation of the protein. PMID:27372901

  8. Study of paraffin-embedded colon cancer tissue using terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Wahaia, Faustino; Kasalynas, Irmantas; Seliuta, Dalius; Molis, Gediminas; Urbanowicz, Andrzej; Carvalho Silva, Catia D.; Carneiro, Fatima; Valusis, Gintaras; Granja, Pedro L.

    2015-01-01

    In this work, samples of non-neoplastic and adenocarcinoma-affected human colon tissue samples were analyzed using multipoint transmission time-domain THz spectroscopy (THz-TDS) to sort out the contrast-contributing factors other than water, the main contrast mechanism factor in in-vivo or in freshly excised bio-tissue. Solving the electromagnetic inverse problem through THz-TDS and, analyzing the transmittance spectra that yielded the frequency-dependent absorption coefficient α and refractive index n of non-neoplastic and neoplastic tissues, we show that it is possible to distinguish between non-neoplastic and neoplastic regions in paraffin-embedded dehydrated. Results and discussion are presented.

  9. Microfluidic Devices for Terahertz Spectroscopy of Live Cells Toward Lab-on-a-Chip Applications

    PubMed Central

    Tang, Qi; Liang, Min; Lu, Yi; Wong, Pak Kin; Wilmink, Gerald J.; D. Zhang, Donna; Xin, Hao

    2016-01-01

    THz spectroscopy is an emerging technique for studying the dynamics and interactions of cells and biomolecules, but many practical challenges still remain in experimental studies. We present a prototype of simple and inexpensive cell-trapping microfluidic chip for THz spectroscopic study of live cells. Cells are transported, trapped and concentrated into the THz exposure region by applying an AC bias signal while the chip maintains a steady temperature at 37 °C by resistive heating. We conduct some preliminary experiments on E. coli and T-cell solution and compare the transmission spectra of empty channels, channels filled with aqueous media only, and channels filled with aqueous media with un-concentrated and concentrated cells. PMID:27049392

  10. Microfluidic Devices for Terahertz Spectroscopy of Live Cells Toward Lab-on-a-Chip Applications.

    PubMed

    Tang, Qi; Liang, Min; Lu, Yi; Wong, Pak Kin; Wilmink, Gerald J; Zhang, Donna; Xin, Hao

    2016-01-01

    THz spectroscopy is an emerging technique for studying the dynamics and interactions of cells and biomolecules, but many practical challenges still remain in experimental studies. We present a prototype of simple and inexpensive cell-trapping microfluidic chip for THz spectroscopic study of live cells. Cells are transported, trapped and concentrated into the THz exposure region by applying an AC bias signal while the chip maintains a steady temperature at 37 °C by resistive heating. We conduct some preliminary experiments on E. coli and T-cell solution and compare the transmission spectra of empty channels, channels filled with aqueous media only, and channels filled with aqueous media with un-concentrated and concentrated cells. PMID:27049392

  11. Studies of Planetary Materials Using Cryogenic Reflectance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Dalton, J. B.; Roush, T. L.; Jamieson, C. S.

    2002-09-01

    Current and planned spacecraft missions to Mars and the Outer Solar System rely on laboratory measurements to facilitate interpretation of remote-sensing data. Solar system objects typically occupy environments far from terrestrial ambient conditions. Compositional studies based on infrared spectroscopy are particularly dependent on laboratory work, as many planetary materials exhibit changes in spectral behavior due to extremes of temperature, pressure, and other influences. The conditions at the surfaces of icy satellites, for example, are difficult to reproduce except under tightly controlled specifications. This is illustrated by comparing the visible and near-infrared reflectance of several materials measured at cryogenic temperatures. Water ice, which is of interest for most solid bodies of the outer solar system, exhibits strong temperature dependence, as does methane ice (Grundy and Schmitt, 1998; Grundy et al., 2002). Hydrated materials, such as salts anticipated to be abundant at Europa, and ammonia hydrates relevant to the Saturnian satellites, also display strong variations with temperature (Dalton and Clark, 1998; McCord et al., 1999; Dalton, 2001). Pyroxenes and olivines, found in rocky bodies including the moon, meteorites, and Mars, also change with temperature (Singer and Roush, 1985; Moroz et al., 2000; Hinrichs and Lucey, 2002). We have initiated a program investigating temperature sensitivity of planetary materials in support of spacecraft missions. Measurements are performed in a cryogenic vacuum environment chamber with a compressed helium cryostat capable of maintaining temperatures as low as 10 Kelvin. We will report on materials such as sulfate hydrates, which display profound spectral changes at low temperatures, and other materials we have measured, such as calcium carbonate, iron sulfide, and tholins (Roush and Dalton, 2002). While many materials are expected to show only modest variations, careful measurement and analysis of planetary

  12. Note: Inverted time-ordering in two-dimensional-Raman-terahertz spectroscopy of water

    NASA Astrophysics Data System (ADS)

    Hamm, Peter; Savolainen, Janne; Ono, Junichi; Tanimura, Yoshitaka

    2012-06-01

    In a previous paper [P. Hamm and J. Savolainen, J. Chem. Phys. 136, 094516 (2012)], 10.1063/1.3691601, we have studied the 2D-Raman-THz response of liquid water, based on an all-atom molecular dynamics simulation. In the pulse sequence we investigated a near-infraredlaser pulse excites a vibrational coherence through a Raman process that switches it into another coherence by a THz pulse after some time, and finally read out by the emission of a THz field.In the present note, we explore the inverted time-ordered pulse sequence, in which the first coherence is generated by a direct THz excitation, while the switching of coherences is achieved by a Raman interaction. Since the dependence of the polarizibility on the nuclear coordinates is more nonlinear compared to that of the dipole moment, this pulse sequence reveals more of the couplings and correlations between the various degrees of freedom of water. Compared to 2D-Raman spectroscopy and the original pulse sequence, this pulse sequence reveals the clearest signature of a photon echo.

  13. Terahertz waveguide emitter with subwavelength confinement

    NASA Astrophysics Data System (ADS)

    Martl, Michael; Darmo, Juraj; Dietze, Daniel; Unterrainer, Karl; Gornik, Erich

    2010-01-01

    The generation of broadband terahertz pulses on the facet of waveguides is presented as an alternative to widely used coupling techniques. Dielectric loaded subwavelength waveguide structures with lateral confinement are investigated with respect to propagating modes and waveguide losses. The results show the terahertz waveguide emitter to be a promising tool for terahertz spectroscopy in the near field and for the probing of microstructured devices such as quantum cascade lasers.

  14. Determination of plant silicon content with near infrared reflectance spectroscopy

    PubMed Central

    Smis, Adriaan; Ancin Murguzur, Francisco Javier; Struyf, Eric; Soininen, Eeva M.; Herranz Jusdado, Juan G.; Meire, Patrick; Bråthen, Kari Anne

    2014-01-01

    Silicon (Si) is one of the most common elements in the earth bedrock, and its continental cycle is strongly biologically controlled. Yet, research on the biogeochemical cycle of Si in ecosystems is hampered by the time and cost associated with the currently used chemical analysis methods. Here, we assessed the suitability of Near Infrared Reflectance Spectroscopy (NIRS) for measuring Si content in plant tissues. NIR spectra depend on the characteristics of the present bonds between H and N, C and O, which can be calibrated against concentrations of various compounds. Because Si in plants always occurs as hydrated condensates of orthosilicic acid (Si(OH)4), linked to organic biomolecules, we hypothesized that NIRS is suitable for measuring Si content in plants across a range of plant species. We based our testing on 442 samples of 29 plant species belonging to a range of growth forms. We calibrated the NIRS method against a well-established plant Si analysis method by using partial least-squares regression. Si concentrations ranged from detection limit (0.24 ppmSi) to 7.8% Si on dry weight and were well predicted by NIRS. The model fit with validation data was good across all plant species (n = 141, R2 = 0.90, RMSEP = 0.24), but improved when only graminoids were modeled (n = 66, R2 = 0.95, RMSEP = 0.10). A species specific model for the grass Deschampsia cespitosa showed even slightly better results than the model for all graminoids (n = 16, R2 = 0.93, RMSEP = 0.015). We show for the first time that NIRS is applicable for determining plant Si concentration across a range of plant species and growth forms, and represents a time- and cost-effective alternative to the chemical Si analysis methods. As NIRS can be applied concurrently to a range of plant organic constituents, it opens up unprecedented research possibilities for studying interrelations between Si and other plant compounds in vegetation, and for addressing the role of Si in ecosystems across a range of Si

  15. Terahertz/mm wave imaging simulation software

    NASA Astrophysics Data System (ADS)

    Fetterman, M. R.; Dougherty, J.; Kiser, W. L., Jr.

    2006-10-01

    We have developed a mm wave/terahertz imaging simulation package from COTS graphic software and custom MATLAB code. In this scheme, a commercial ray-tracing package was used to simulate the emission and reflections of radiation from scenes incorporating highly realistic imagery. Accurate material properties were assigned to objects in the scenes, with values obtained from the literature, and from our own terahertz spectroscopy measurements. The images were then post-processed with custom Matlab code to include the blur introduced by the imaging system and noise levels arising from system electronics and detector noise. The Matlab code was also used to simulate the effect of fog, an important aspect for mm wave imaging systems. Several types of image scenes were evaluated, including bar targets, contrast detail targets, a person in a portal screening situation, and a sailboat on the open ocean. The images produced by this simulation are currently being used as guidance for a 94 GHz passive mm wave imaging system, but have broad applicability for frequencies extending into the terahertz region.

  16. Reflectance spectroscopy in planetary science: Review and strategy for the future

    NASA Technical Reports Server (NTRS)

    Mccord, Thomas B. (Editor)

    1987-01-01

    Reflectance spectroscopy is a remote sensing technique used to study the surfaces and atmospheres of solar system bodies. It provides first-order information on the presence and amounts of certain ions, molecules, and minerals on a surface or in an atmosphere. Reflectance spectroscopy has become one of the most important investigations conducted on most current and planned NASA Solar System Exploration Program space missions. This book reviews the field of reflectance spectroscopy, including information on the scientific technique, contributions, present conditions, and future directions and needs.

  17. Tethered bilayer lipid membranes studied by simultaneous attenuated total reflectance infrared spectroscopy and electrochemical impedance spectroscopy

    PubMed Central

    Erbe, Andreas; Bushby, Richard J.; Evans, Stephen D.; Jeuken, Lars J. C.

    2013-01-01

    The formation of tethered lipid bilayer membranes (tBLMs) from unilamelar vesicles of egg yolk phosphatidylcholine (EggPC) on mixed self–assembled monolayers (SAMs) from varying ratios of 6-mercaptohexanol and EO3Cholesteryl on gold has been monitored by simultaneous attenuated total reflectance fourier transform infrared (ATR–FTIR) spectroscopy and electrochemical impedance spectroscopy (EIS). The influence of the lipid orientation (and hence the anisotropy) of lipids on a gold film on the dichroic ratio was studied by simulations of spectra with a matrix method for anisotropic layers. It is shown that for certain tilt angles of the dielectric tensor of the adsorbed anisotropic layer dispersive and negative absorption bands are possible. The experimental data indicates that the structure of the assemblies obtained varies with varying SAM composition. On SAMs with a high content of EO3Cholesteryl, tBLMs with reduced fluidity are formed. For SAMs with high content of 6-mercaptohexanol, the results are consistent with the adsorption of flattened vesicles, while spherical vesicles have been found in a small range of surface compositions. The kinetics of the adsorption process is consistent with the assumption of spherical vesicles as long–living intermediates for surfaces of high 6-mercaptohexanol content. No long–living spherical vesicles have been detected for surfaces with large fraction of EO3Cholesteryl tethers. The observed differences between the surfaces suggest that for the formation of tBLMs (unlike supported BLMs) no critical surface coverage of vesicles is needed prior to lipid bilayer formation. PMID:17388505

  18. Reflectance spectroscopy: quantitative analysis techniques for remote sensing applications.

    USGS Publications Warehouse

    Clark, R.N.; Roush, T.L.

    1984-01-01

    Several methods for the analysis of remotely sensed reflectance data are compared, including empirical methods and scattering theories, both of which are important for solving remote sensing problems. The concept of the photon mean path length and the implications for use in modeling reflectance spectra are presented.-from Authors

  19. Trends in Terahertz Device and System Technologies

    NASA Astrophysics Data System (ADS)

    Nagatsuma, Tadao

    Terahertz (THz) electromagnetic waves, which cover an unexplored portion of spectrum between infrared and microwaves at frequencies from 100 GHz to 10 THz, have been expected to offer innovations in sensing, imaging, spectroscopy, and communications. This paper reviews recent advances in the terahertz technology, focusing on recent system applications and key devices to enable practical use.

  20. Femtosecond terahertz time-domain spectroscopy at 36 kHz scan rate using an acousto-optic delay

    NASA Astrophysics Data System (ADS)

    Urbanek, B.; Möller, M.; Eisele, M.; Baierl, S.; Kaplan, D.; Lange, C.; Huber, R.

    2016-03-01

    We present a rapid-scan, time-domain terahertz spectrometer employing femtosecond Er:fiber technology and an acousto-optic delay with attosecond precision, enabling scanning of terahertz transients over a 12.4-ps time window at a waveform refresh rate of 36 kHz, and a signal-to-noise ratio of 1.7 × 105 / √{ H z } . Our approach enables real-time monitoring of dynamic THz processes at unprecedented speeds, which we demonstrate through rapid 2D thickness mapping of a spinning teflon disc at a precision of 10 nm/ √{ H z } . The compact, all-optical design ensures alignment-free operation even in harsh environments.

  1. On Ultrafast Time-Domain TeraHertz Spectroscopy in the Condensed Phase: Linear Spectroscopic Measurements of Hydrogen-Bond Dynamics of Astrochemical Ice Analogs and Nonlinear TeraHertz Kerr Effect Measurements of Vibrational Quantum Beats

    NASA Astrophysics Data System (ADS)

    Allodi, Marco A.

    Much of the chemistry that affects life on planet Earth occurs in the condensed phase. The TeraHertz (THz) or far-infrared (far-IR) region of the electromagnetic spectrum (from 0.1 THz to 10 THz) has been shown to provide unique possibilities in the study of condensed-phase processes. The goal of this work is to expand the possibilities available in the THz region and undertake new investigations of fundamental interest to chemistry. Since we are fundamentally interested in condensed-phase processes, this thesis focuses on two areas where THz spectroscopy can provide new understanding: astrochemistry and solvation science. To advance these fields, we had to develop new instrumentation that would enable the experiments necessary to answer new questions in either astrochemistry or solvation science. We first developed a new experimental setup capable of studying astrochemical ice analogs in both the TeraHertz (THz), or far-Infrared (far-IR), region (0.3 - 7.5 THz; 10 - 250 wavenumbers) and the mid-IR (400 - 4000 wavenumbers). The importance of astrochemical ices lies in their key role in the formation of complex organic molecules, such as amino acids and sugars in space. Thus, the instruments are capable of performing variety of spectroscopic studies that can provide especially relevant laboratory data to support astronomical observations from telescopes such as the Herschel Space Telescope, the Stratospheric Observatory for Infrared Astronomy (SOFIA), and the Atacama Large Millimeter Array (ALMA). The experimental apparatus uses a THz time-domain spectrometer, with a 1750/875 nm plasma source and a GaP detector crystal, to cover the bandwidth mentioned above with 10 GHz (0.3 wavenumber) resolution. Using the above instrumentation, experimental spectra of astrochemical ice analogs of water and carbon dioxide in pure, mixed, and layered ices were collected at different temperatures under high-vacuum conditions with the goal of investigating the structure of the ice

  2. Softening of infrared-active mode of perovskite BaZrO{sub 3} proved by terahertz time-domain spectroscopy

    SciTech Connect

    Helal, M. A.; Mori, T.; Kojima, S.

    2015-05-04

    The low-frequency infrared-active optical modes were studied in a barium zirconate, BaZrO{sub 3}, single crystal with the perovskite structure using terahertz (THz) time-domain spectroscopy (TDS). The real and imaginary parts of the dielectric constants were accurately determined in the frequency range between 0.2 and 2.7 THz. Upon cooling from room temperature to 8 K, the lowest-frequency TO1 mode at 2.32 THz showed a pronounced softening to 1.94 THz. The real part of the dielectric constant at 0.5 THz determined by THz-TDS obeys Barrett's relation, and the existence of a plateau confirms that the quantum effects lead to saturation of the soft mode frequencies of the TO1 and TO2 modes below ≈20 K. This is reminiscent of incipient ferroelectrics with the perovskite structure such as CaTiO{sub 3}.

  3. Photoinduced insulator-metal phase transition and the metallic phase propagation in VO2 films investigated by time-resolved terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Xue, Xin; Jiang, Meng; Li, Gaofang; Lin, Xian; Ma, Guohong; Jin, Ping

    2013-11-01

    The particle size and film thickness dependence of the photoinduced insulator-metal phase transition in VO2 films has been studied systematically by time-resolved terahertz spectroscopy at room temperature. It is found that the dynamical photoinduced phase transition from insulator to metal consists of two processes: a 1.7 ps fast process and a slow process with a typical time constant of 40 ps. Both of the two processes show particle size independence. The 40 ps slow process is revealed to arise from the longitudinal propagation of the metallic phase from the photoexcited surface to the interior of the VO2 film. A phase boundary propagation speed with a magnitude of ˜2400 m/s is obtained, which is close to the velocity of sound in solid materials and coincides with the prediction of diffusionless phase transformation. Our experimental results clearly establish the entire procedure of photoinduced phase change in the VO2 film.

  4. Employing time-resolved terahertz spectroscopy to analyze carrier dynamics in thin-film Cu{sub 2}ZnSn(S,Se){sub 4} absorber layers

    SciTech Connect

    Guglietta, Glenn W.; Baxter, Jason B.; Choudhury, Kaushik Roy; Caspar, Jonathan V.

    2014-06-23

    We report the application of time-resolved terahertz spectroscopy (TRTS) to measure photoexcited carrier lifetimes and mobility, and to determine recombination mechanisms in Cu{sub 2}ZnSn(S,Se){sub 4} (CZTSSe) thin films fabricated from nanocrystal inks. Ultrafast time resolution permits tracking the evolution of carrier density to determine recombination rates and mechanisms. The carrier generation profile was manipulated by varying the photoexcitation wavelength and fluence to distinguish between surface, Shockley-Read-Hall (SRH), radiative, and Auger recombination mechanisms and determine rate constants. Surface and SRH recombination are the dominant mechanisms for the air/CZTSSe/SiO{sub 2}/Si film stack. Diffusion to, and then recombination at, the air-CZTSSe interface occurred on the order of 100 picoseconds, while SRH recombination lifetimes were 1–2 nanoseconds. TRTS measurements can provide information that is complementary to conventional time-resolved photoluminescence measurements and can direct the design of efficient thin film photovoltaics.

  5. Correlation between salt-induced change in water structure and lipid structure of multi-lamellar vesicles observed by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Choi, Da-Hye; Son, Heyjin; Jeong, Jin-Young; Park, Gun-Sik

    2016-08-01

    Salt-induced change in the structure of water molecules inside multi-lamellar vesicles is experimentally studied with terahertz time-domain spectroscopy. The complex dielectric constant of 1, 2-ditetradecanoyl-sn-glycero-3-phosphocholine model membranes dispersed in NaCl solution with different salt concentrations are measured. Structure of water molecules in the solution is characterized from the measured dielectric constant using Debye relaxation model. Combined with small-angle X-ray scattering observation, it is found that salt-induced change of water structure, especially fast water fraction, show strong correlation with the increase in nanometer-scale multi-lamellar repeat space. This suggests that water could be critical in nanometer-scale membrane-membrane communications.

  6. Transmittance, Reflectance, and Emission Spectroscopy of Meteorites from the UV to the IR Spectral Range

    NASA Astrophysics Data System (ADS)

    Maturilli, A.; Helbert, J.; Koulen, J. M.; Ferrari, S.; Martellato, E.

    2016-08-01

    Transmittance, reflectance, and emissivity Spectra of six meteorites have been collected at the Planetary Spectroscopy Laboratory (PSL) of DLR in Berlin in the whole spectral range from the UV to the IR.

  7. Terahertz metamaterials

    DOEpatents

    Peralta, Xomalin Guaiuli; Brener, Igal; O'Hara, John; Azad, Abul; Smirnova, Evgenya; Williams, John D.; Averitt, Richard D.

    2014-08-12

    Terahertz metamaterials comprise a periodic array of resonator elements disposed on a dielectric substrate or thin membrane, wherein the resonator elements have a structure that provides a tunable magnetic permeability or a tunable electric permittivity for incident electromagnetic radiation at a frequency greater than about 100 GHz and the periodic array has a lattice constant that is smaller than the wavelength of the incident electromagnetic radiation. Microfabricated metamaterials exhibit lower losses and can be assembled into three-dimensional structures that enable full coupling of incident electromagnetic terahertz radiation in two or three orthogonal directions. Furthermore, polarization sensitive and insensitive metamaterials at terahertz frequencies can enable new devices and applications.

  8. Doppler-shifted reflections of X rays in beamfoil spectroscopy

    NASA Technical Reports Server (NTRS)

    Bernstein, E. M.; Mcintyre, L. C., Jr.

    1976-01-01

    Carbon foils were positioned at roughly 10 deg to the conventional perpendicular position so that the spectrometer would view the beam on emergence from the foil, with no radiation shielded by a bowed or wrinkled foil or by the foil holder. Extraneous peaks due to reflected radiation were detected in the spectrum obtained with the tilted foil. A large satellite appears longward of the spectral line and is attributed to Doppler-shifted radiation reflected from the foil surface. Special tests arranged to validate the origin of the satellites are described. The relative intensity of the reflected radiation compared with the direct radiation observed is at variance with the relative intensities reported for longer wavelengths. The reasons for this, possible effects of spectrometer geometry, and applications in the investigation or generation of polarization remain to be investigated

  9. Far infrared (terahertz) spectroscopy of a series of polycyclic aromatic hydrocarbons and application to structure interpretation of asphaltenes and related compounds.

    PubMed

    Cataldo, Franco; Angelini, Giancarlo; García-Hernández, D Aníbal; Manchado, Arturo

    2013-07-01

    A series of 33 different polycyclic aromatic hydrocarbons (PAHs) were studied by far infrared spectroscopy (terahertz spectroscopy) in the spectral range comprised between 600 and 50 cm(-1). In addition to common PAHs like naphthalene, anthracene, phenanthrene, fluoranthene, picene, pyrene, benzo[α]pyrene, and perylene, also quite unusual PAHs were studied like tetracene, pentacene, acenaphtene, acenaphtylene, triphenylene, and decacyclene. A series of alkylated naphthalenes and anthracenes were studied as well as methypyrene. Partially or totally hydrogenated PAHs were also object of the present investigation, ranging from tetrahydronaphthalene (tetralin) to decahydronaphthalene (decalin), 9,10-dihydroanthracene, 9,10-dihydrophenanthrene, hexahydropyrene, and dodecahydrotriphenylene. Finally, the large and quite rare PAHs coronene, quaterrylene, hexabenzocoronene, and dicoronylene were studied by far infrared spectroscopy. The resulting reference spectra were used in the interpretation of the chemical structure of asphaltenes (as extracted from a heavy petroleum fraction and from bitumen), the chemical structures of other petroleum fractions known as DAE (distillate aromatic extract) and RAE (residual aromatic extract), and a possible interpretation of components of the chemical structure of anthracite coal. Asphaltenes, heavy petroleum fractions, and coal were proposed as model compounds for the interpretation of the emission spectra of certain proto-planetary nebulae (PPNe) with a good matching in the mid infrared between the band pattern of the PPNe emission spectra and the spectra of these oil fractions or coal. Although this study was finalized in an astrochemical context, it may find application also in the petroleum and coal chemistry. PMID:23603577

  10. Far infrared (terahertz) spectroscopy of a series of polycyclic aromatic hydrocarbons and application to structure interpretation of asphaltenes and related compounds.

    PubMed

    Cataldo, Franco; Angelini, Giancarlo; García-Hernández, D Aníbal; Manchado, Arturo

    2013-07-01

    A series of 33 different polycyclic aromatic hydrocarbons (PAHs) were studied by far infrared spectroscopy (terahertz spectroscopy) in the spectral range comprised between 600 and 50 cm(-1). In addition to common PAHs like naphthalene, anthracene, phenanthrene, fluoranthene, picene, pyrene, benzo[α]pyrene, and perylene, also quite unusual PAHs were studied like tetracene, pentacene, acenaphtene, acenaphtylene, triphenylene, and decacyclene. A series of alkylated naphthalenes and anthracenes were studied as well as methypyrene. Partially or totally hydrogenated PAHs were also object of the present investigation, ranging from tetrahydronaphthalene (tetralin) to decahydronaphthalene (decalin), 9,10-dihydroanthracene, 9,10-dihydrophenanthrene, hexahydropyrene, and dodecahydrotriphenylene. Finally, the large and quite rare PAHs coronene, quaterrylene, hexabenzocoronene, and dicoronylene were studied by far infrared spectroscopy. The resulting reference spectra were used in the interpretation of the chemical structure of asphaltenes (as extracted from a heavy petroleum fraction and from bitumen), the chemical structures of other petroleum fractions known as DAE (distillate aromatic extract) and RAE (residual aromatic extract), and a possible interpretation of components of the chemical structure of anthracite coal. Asphaltenes, heavy petroleum fractions, and coal were proposed as model compounds for the interpretation of the emission spectra of certain proto-planetary nebulae (PPNe) with a good matching in the mid infrared between the band pattern of the PPNe emission spectra and the spectra of these oil fractions or coal. Although this study was finalized in an astrochemical context, it may find application also in the petroleum and coal chemistry.

  11. Monitoring bruise age using visible diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    McMurdy, John W.; Duffy, Susan; Crawford, Gregory P.

    2007-02-01

    The ability to determine the age of a bruise of unknown age mechanism is important in matters of domestic and child abuse and forensics. While physicians are asked to make clinical judgment on the age of a bruise using color and tenderness, studies have shown that a physicians estimate is highly inaccurate and in cases no better than chance alone. We present here the temporal progression of reflection spectrum collected from accidentally inflicted contusions in adult and child study participants with a synopsis of the observed phenomena. Reflection spectra collected using a portable fiber optic reflection spectrometer can track the increase in extravasated hemoglobin from trauma caused blood vessel rupture and subsequent removal of this hemoglobin occurring concurrent with an increase in the absorption attributed to the breakdown product bilirubin. We hypothesize that this time dependent pattern can be used to determine the age of an unknown bruise in an individual provided rate constant information for the patient can be determined in a controlled calibration bruise. Using reflection spectra to estimate bruise age can provide a rapid and noninvasive method to improve the ability of physicians in dating the age of a contusion.

  12. Terahertz time-domain reflectometry of multilayered systems

    NASA Astrophysics Data System (ADS)

    Jackson, J. Bianca

    Presented in this work are applications of terahertz pulse ranging, spectroscopy and imaging to the nondestructive evaluation of three disparate multilayer systems for the detection and measurement of hidden layers, as well as the extraction of system information that will aid in its maintenance, repair or replacement. Thermal protection systems for turbine engine components were investigated. Thermal barrier coatings (TBC) and thermally-grown oxide (TGO) thicknesses were determined with 10 micron resolution using time-of-flight and refractive index calculations. Two alternative methods of monitoring TGO growth using reflection amplitudes and spectral shifts were proposed for the prediction of TBC failure. Laser-machined defects as narrow as 50 microns were resolved in one- and two-dimensional images. The light and dark rings of trees, which reflect the changes in tree growth density over the course of a year, are measurable using pulsed terahertz beams. Tree-rings of bare and painted wood specimen were laterally and axially tomographically imaged in order to facilitate the dendrochronological cross-dating of artifacts. Comparisons were made between photographs and terahertz images to demonstrate the reliability of the technique. Historically, numerous unique artworks have been lost through the act of being covered over time. Samples of paintings, drawings and mosaics were imaged beneath layers of paint and plaster using pulsed-terahertz techniques to demonstrate the efficacy of the technique for art history and restoration. Sketch materials and pigments were measured, between 0.05 and 1.0 THz, to help identify colors in spectroscopic images. Other computational and processing methods were used to optimize the distinction between color domains. Additional time-domain terahertz applications for the examination of artwork and other artifacts were proposed.

  13. Terahertz pulsed imaging in vivo

    NASA Astrophysics Data System (ADS)

    Pickwell-MacPherson, E.

    2011-03-01

    Terahertz (1012 Hz) pulsed imaging is a totally non-destructive and non-ionising imaging modality and thus potential applications in medicine are being investigated. In this paper we present results using our hand-held terahertz probe that has been designed for in vivo use. In particular, we use the terahertz probe to perform reflection geometry in vivo measurements of human skin. The hand-held terahertz probe gives more flexibility than a typical flat-bed imaging system, but it also results in noisier data and requires existing processing methods to be improved. We describe the requirements and limitations of system geometry, data acquisition rate, image resolution and penetration depth and explain how various factors are dependent on each other. We show how some of the physical limitations can be overcome using novel data processing methods.

  14. ChemCam Passive Reflectance Spectroscopy at Gale Crater, Mars

    NASA Astrophysics Data System (ADS)

    Johnson, J. R.; Bell, J. F.; Cloutis, E.; Bender, S.; Blaney, D. L.; Ehlmann, B. L.; Gasnault, O.; Kinch, K. M.; Le Mouelic, S.; Rice, M. S.; Wiens, R. C.; DeFlores, L.; Team, M.

    2013-12-01

    The Laser-Induced Breakdown Spectrometer (LIBS) portion of the ChemCam instrument on the Mars Science Laboratory Curiosity rover uses 3 dispersive spectrometers to cover the ultraviolet (240-342 nm), visible (382-469 nm) and visible/near-infrared (474-906 nm) spectral regions at high spectral (<0.5nm) and spatial (0.65mrad) resolution. In active LIBS mode, light emitted from a laser-generated plasma is dispersed onto these spectrometers and used to detect elemental emission lines. Typical observations include 3 msec-exposure 'dark' spectra (acquired with the LIBS laser off) used to remove the background signal from the LIBS measurement. Similar 'passive' observations of the ChemCam calibration target holder can be made at similar times of day and at identical exposure times (to minimize variations from dark current). Because this target exhibits ~95% flat reflectance in the ~400-900 nm region, radiance spectra ratios (surface/calibration target) can be normalized to known calibration target lab spectra to produce relative reflectance spectra (400-900 nm) with an estimated accuracy of 10-20%. Initial results replicated the known spectral shape and overall reflectance values of the ChemCam calibration targets and green color chip on the Mastcam calibration target. Dust contamination was evident, although dust on the ChemCam calibration targets is minimized by their tilted placement on the rover deck. All ChemCam targets that were sunlit during LIBS acquisition (~80% of all measurements) provide 'dark' spectra for which relative reflectance spectra can be obtained. Owing to the dusty nature of the Gale landing sites, passive spectra observed to date exhibit spectral shapes indicative of ferric phases, similar to spectra of palagonitic soils. Most spectra are bracketed in reflectance by typical 'bright' and 'dark' spectra from the OMEGA and CRISM orbital spectrometers. Preliminary Mastcam reflectance spectra are similar, providing additional confidence regarding the

  15. Microwave Reflection Spectroscopy of a Two-Dimensional Electron Gas

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Liu, Ruiyuan; Du, Lingjie; Du, Rui-Rui; Pfeiffer, Loren; West, Ken

    Cyclotron resonance (CR) is a standard method to determine the carrier effective mass in two-dimensional electron systems, typically by measuring/analyzing the absorption or transmission signal. Here we report a microwave spectrometer utilizing the reflection signal. In our experiment setup based on a top-loading helium3 cryostat and a superconducting solenoid, the microwave (up to 40GHz) is sent down via a coax cable to the sample surface, and the reflection signal is then collected by the same cable and fed upward to a directional coupler, and being detected. We demonstrate the applicability of the spectrometer by measuring the CR of high-mobility electrons or holes in GaAs/AlGaAs quantum wells. The construction of spectrometer, preliminary data, and brief discussions will be presented. The work at Rice was supported by Welch Foundation Grant C-1682.

  16. [Application of near infrared reflectance spectroscopy to predict meat chemical compositions: a review].

    PubMed

    Tao, Lin-Li; Yang, Xiu-Juan; Deng, Jun-Ming; Zhang, Xi

    2013-11-01

    In contrast to conventional methods for the determination of meat chemical composition, near infrared reflectance spectroscopy enables rapid, simple, secure and simultaneous assessment of numerous meat properties. The present review focuses on the use of near infrared reflectance spectroscopy to predict meat chemical compositions. The potential of near infrared reflectance spectroscopy to predict crude protein, intramuscular fat, fatty acid, moisture, ash, myoglobin and collagen of beef, pork, chicken and lamb is reviewed. This paper discusses existing questions and reasons in the current research. According to the published results, although published results vary considerably, they suggest that near-infrared reflectance spectroscopy shows a great potential to replace the expensive and time-consuming chemical analysis of meat composition. In particular, under commercial conditions where simultaneous measurements of different chemical components are required, near infrared reflectance spectroscopy is expected to be the method of choice. The majority of studies selected feature-related wavelengths using principal components regression, developed the calibration model using partial least squares and modified partial least squares, and estimated the prediction accuracy by means of cross-validation using the same sample set previously used for the calibration. Meat fatty acid composition predicted by near-infrared spectroscopy and non-destructive prediction and visualization of chemical composition in meat using near-infrared hyperspectral imaging and multivariate regression are the hot studying field now. On the other hand, near infrared reflectance spectroscopy shows great difference for predicting different attributes of meat quality which are closely related to the selection of calibration sample set, preprocessing of near-infrared spectroscopy and modeling approach. Sample preparation also has an important effect on the reliability of NIR prediction; in particular

  17. Three-dimensional invisibility cloaks functioning at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Cao, Wei; Zhou, Fan; Liang, Dachuan; Gu, Jianqiang; Han, Jiaguang; Sun, Cheng; Zhang, Weili

    2014-05-01

    Quasi-three-dimensional invisibility cloaks, comprised of either homogeneous or inhomogeneous media, are experimentally demonstrated in the terahertz regime. The inhomogeneous cloak was lithographically fabricated using a scalable Projection Microstereolithography process. The triangular cloaking structure has a total thickness of 4.4 mm, comprised of 220 layers of 20 μm thickness. The cloak operates at a broad frequency range between 0.3 and 0.6 THz, and is placed over an α-lactose monohydrate absorber with rectangular shape. Characterized using angular-resolved reflection terahertz time-domain spectroscopy, the results indicate that the terahertz invisibility cloak has successfully concealed both the geometrical and spectroscopic signatures of the absorber, making it undetectable to the observer. The homogeneous cloaking device made from birefringent crystalline sapphire features a large concealed volume, low loss, and broad bandwidth. It is capable of hiding objects with a dimension nearly an order of magnitude larger than that of its lithographic counterpart, but without involving complex and time-consuming cleanroom processing. The cloak device was made from two 20-mm-thick high-purity sapphire prisms. The cloaking region has a maximum height 1.75 mm with a volume of approximately 5% of the whole sample. The reflected TM beam from the cloak shows nearly the same profile as that reflected by a flat mirror.

  18. Interaction of Sensitizing Dyes with Nanostructured TiO2 Film in Dye-Sensitized Solar Cells Using Terahertz Spectroscopy

    PubMed Central

    Ghann, William; Rahman, Aunik; Rahman, Anis; Uddin, Jamal

    2016-01-01

    The objective of this investigation was to shed light on the nature of interaction of different organic dyes and an inorganic dye, Ruthenium (II) polypyridine complex, with TiO2 nanoparticles. TiO2 is commonly deployed as an efficient energy transfer electrode in dye sensitized solar cells. The efficiency of dye sensitized solar cells is a function of the interaction of a dye with the electrode material such as TiO2. To the best of our knowledge the present study is the first effort in the determination of terahertz absorbance signals, investigation of real-time dye permeation kinetics, and the surface profiling and 3D imaging of dye sensitized TiO2 films. Herein, we report that the terahertz spectra of the natural dye sensitized TiO2 films were distinctively different from that of the inorganic dye with prominent absorption of natural dyes occurring at approximately the same wavelength. It was observed that the permeation of the natural dyes were more uniform through the layers of the mesoporous TiO2 compared to the inorganic dye. Finally, defects and flaws on TiO2 film were easily recognized via surface profiling and 3D imaging of the films. The findings thus offer a new approach in characterization of dye sensitized solar cells. PMID:27443236

  19. Interaction of Sensitizing Dyes with Nanostructured TiO2 Film in Dye-Sensitized Solar Cells Using Terahertz Spectroscopy.

    PubMed

    Ghann, William; Rahman, Aunik; Rahman, Anis; Uddin, Jamal

    2016-07-22

    The objective of this investigation was to shed light on the nature of interaction of different organic dyes and an inorganic dye, Ruthenium (II) polypyridine complex, with TiO2 nanoparticles. TiO2 is commonly deployed as an efficient energy transfer electrode in dye sensitized solar cells. The efficiency of dye sensitized solar cells is a function of the interaction of a dye with the electrode material such as TiO2. To the best of our knowledge the present study is the first effort in the determination of terahertz absorbance signals, investigation of real-time dye permeation kinetics, and the surface profiling and 3D imaging of dye sensitized TiO2 films. Herein, we report that the terahertz spectra of the natural dye sensitized TiO2 films were distinctively different from that of the inorganic dye with prominent absorption of natural dyes occurring at approximately the same wavelength. It was observed that the permeation of the natural dyes were more uniform through the layers of the mesoporous TiO2 compared to the inorganic dye. Finally, defects and flaws on TiO2 film were easily recognized via surface profiling and 3D imaging of the films. The findings thus offer a new approach in characterization of dye sensitized solar cells.

  20. Interaction of Sensitizing Dyes with Nanostructured TiO2 Film in Dye-Sensitized Solar Cells Using Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ghann, William; Rahman, Aunik; Rahman, Anis; Uddin, Jamal

    2016-07-01

    The objective of this investigation was to shed light on the nature of interaction of different organic dyes and an inorganic dye, Ruthenium (II) polypyridine complex, with TiO2 nanoparticles. TiO2 is commonly deployed as an efficient energy transfer electrode in dye sensitized solar cells. The efficiency of dye sensitized solar cells is a function of the interaction of a dye with the electrode material such as TiO2. To the best of our knowledge the present study is the first effort in the determination of terahertz absorbance signals, investigation of real-time dye permeation kinetics, and the surface profiling and 3D imaging of dye sensitized TiO2 films. Herein, we report that the terahertz spectra of the natural dye sensitized TiO2 films were distinctively different from that of the inorganic dye with prominent absorption of natural dyes occurring at approximately the same wavelength. It was observed that the permeation of the natural dyes were more uniform through the layers of the mesoporous TiO2 compared to the inorganic dye. Finally, defects and flaws on TiO2 film were easily recognized via surface profiling and 3D imaging of the films. The findings thus offer a new approach in characterization of dye sensitized solar cells.

  1. Interaction of Sensitizing Dyes with Nanostructured TiO2 Film in Dye-Sensitized Solar Cells Using Terahertz Spectroscopy.

    PubMed

    Ghann, William; Rahman, Aunik; Rahman, Anis; Uddin, Jamal

    2016-01-01

    The objective of this investigation was to shed light on the nature of interaction of different organic dyes and an inorganic dye, Ruthenium (II) polypyridine complex, with TiO2 nanoparticles. TiO2 is commonly deployed as an efficient energy transfer electrode in dye sensitized solar cells. The efficiency of dye sensitized solar cells is a function of the interaction of a dye with the electrode material such as TiO2. To the best of our knowledge the present study is the first effort in the determination of terahertz absorbance signals, investigation of real-time dye permeation kinetics, and the surface profiling and 3D imaging of dye sensitized TiO2 films. Herein, we report that the terahertz spectra of the natural dye sensitized TiO2 films were distinctively different from that of the inorganic dye with prominent absorption of natural dyes occurring at approximately the same wavelength. It was observed that the permeation of the natural dyes were more uniform through the layers of the mesoporous TiO2 compared to the inorganic dye. Finally, defects and flaws on TiO2 film were easily recognized via surface profiling and 3D imaging of the films. The findings thus offer a new approach in characterization of dye sensitized solar cells. PMID:27443236

  2. Diffuse reflectance spectroscopy of pre- and post-treated oral submucous fibrosis: an in vivo study

    NASA Astrophysics Data System (ADS)

    Sivabalan, S.; Ponranjini Vedeswari, C.; Jayachandran, S.; Koteeswaran, D.; Pravda, C.; Aruna, P.; Ganesan, S.

    2010-02-01

    Oral submucous fibrosis (OSF) is a high risk precancerous condition characterized by changes in the connective tissue fibers of the lamina propria and deeper parts leading to stiffness of the mucosa and restricted mouth opening, fibrosis of the lining mucosa of the upper digestive tract involving the oral cavity, oro- and hypo-pharynx and the upper two-thirds of the oesophagus. Optical reflectance measurements have been used to extract diagnostic information from a variety of tissue types, in vivo. We apply diffuse reflectance spectroscopy to quantitatively monitor tumour response to chemotherapy. Twenty patients with submucous fibrosis were diagnosed with diffuse reflectance spectroscopy and treated with the chemotherapy drug, Dexamethasone sodium phosphate and Hyaluronidase injection for seven weeks and after the treatment they were again subjected to the diffuse reflectance spectroscopy. The major observed spectral alterations on pre and post treated submucous fibrosis is an increase in the diffuse reflectance from 450 to 600 nm. Normal mucosa has showed higher reflectance when compared to the pre and post-treated cases. The spectral changes were quantified and correlated to conventional diagnostic results viz., maximum mouth opening, tongue protrusion and burning sensation. The results of this study suggest that the diffuse reflectance spectroscopy may also be considered as complementary optical techniques to monitor oral tissue transformation.

  3. Cavity enhanced terahertz modulation

    SciTech Connect

    Born, N.; Scheller, M.; Moloney, J. V.; Koch, M.

    2014-03-10

    We present a versatile concept for all optical terahertz (THz) amplitude modulators based on a Fabry-Pérot semiconductor cavity design. Employing the high reflectivity of two parallel meta-surfaces allows for trapping selected THz photons within the cavity and thus only a weak optical modulation of the semiconductor absorbance is required to significantly damp the field within the cavity. The optical switching yields to modulation depths of more than 90% with insertion efficiencies of 80%.

  4. Catheter based mid-infrared reflectance and reflectance generated absorption spectroscopy

    SciTech Connect

    Holman, Hoi-Ying N

    2013-10-29

    A method of characterizing conditions in a tissue, by (a) providing a catheter that has a light source that emits light in selected wavenumbers within the range of mid-IR spectrum; (b) directing the light from the catheter to an area of tissue at a location inside a blood vessel of a subject; (c) collecting light reflected from the location and generating a reflectance spectra; and (d) comparing the reflectance spectra to a reference spectra of normal tissue, whereby a location having an increased number of absorbance peaks at said selected wavenumbers indicates a tissue inside the blood vessel containing a physiological marker for atherosclerosis.

  5. Reflectance spectroscopy of mineral samples at IAS/Orsay laboratory

    NASA Astrophysics Data System (ADS)

    Bonello, G.; Bibring, J. P.; Erard, S.; D'Hendecourt, L.; Bardintzeff, J. M.; Platevoet, B.

    2003-04-01

    In the last 20 years, imaging spectrometry in the visible and infrared onboard spacecraft has become an essential technique to study surfaces of planetary objects, prior and in addition to in-situ investigations. Remote sensing experiments analysing the sunlight reflected or emitted by planetary surfaces can be used to derive the mineralogical composition and physical properties of the natural surfaces observed. This technique was successfully used on many probes and will be improved as a main contribution of future missions to study several Solar System objects as Mercury (BEPI-COLOMBO), Venus (VENUS-EXPRESS), the Moon (SMART-1), Mars (MARS-EXPRESS, MRO...), Asteroids (ROSETTA, DAWN...), giant planet satellites (GALILEO, CASSINI) and comets (ROSETTA), increasing our knowledge of the formation and evolution of each object and leading to constrain the Solar System own ones. Nevertheless, the detection of diagnostic features in the spectrum acquired in order to identify mineral species needs the support of spectral database made with earth natural samples. Furthermore, the reflectance spectrum deconvolution to mineral abundance in an unambiguous way is difficult because the spectra can be complex non-linear functions of grain size, abundance, material opacity, and type of mixtures (intra, intimate, area mixtures). Ground support laboratory measurements are thus essential to interpret the spectra in terms of main chemical composition and improve the radiative transfer in particulate media modelling to deduce relative abundances. As part as some past and future instruments and being greatly concerned by the scientific background of surface geology topic, the IAS laboratory in Orsay develops a facility to achieve these goals. It consists of a Brücker IFS66V FTIR spectrometer combined with two Graseby toolkits that permit to measure reflectance of mineral samples (solid or powder). The first one is mounted in a fix biconical configuration, whereas the second one is a bi

  6. Detection of propranolol in pharmaceutical formulations by diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Gotardo, Mara Andréia; Tognolli, João Olímpio; Pezza, Helena Redigolo; Pezza, Leonardo

    2008-04-01

    This paper describes an analytical reflectometric method that has an objective not only the industrial quality control but also to detect possible falsifications and/or adulterations of propranolol in pharmaceutical formulations. The method is based on the diffuse reflectance measurements of the colored product (III) of the spot test reaction between propranolol hydrochloride (I) and 2,6-dichloroquinone-4-chloroimide (II) using filter paper as solid support. Spot test conditions have been investigated using experimental design in order to identify and optimize the critical factors. The factors evaluated were DCQ concentration, propranolol solvent and DCQ solvent. The best reaction conditions were achieved with the addition of 30 μL of propranolol solution in ethanol 35% (v/v) and 30 μL of DCQ solution at 70 mg mL -1 in acetone, in this order. All reflectance measurements were carried out at 500 nm and the linear range was from 8.45 × 10 -4 to 8.45 × 10 -2 mol L -1 ( r = 0.998). The limit of detection was 1.01 × 10 -4 mol L -1. No interference was observed from the assessed excipients and drugs. The method was applied to determine propranolol in commercial brands of pharmaceuticals. The results obtained by the proposed method were favorably compared with those given by the British Pharmacopoeia procedure.

  7. Near-Earth asteroids: possible sources from reflectance spectroscopy.

    PubMed

    McFadden, L A; Gaffey, M J; McCord, T B

    1985-07-12

    Spectra of near-Earth asteroids were compared to spectra of selected asteroids, planets, and satellites to determine possible source regions. The diversity of reflectance spectra of the near-Earth asteroids implies different mineralogical compositions and hence more than one source region. The presence of near-Earth asteroid spectral signatures similar to those of certain main-belt asteroids supports models that derive some of these asteroids from the 5:2 Kirkwood gap and the Flora family by gravitational perturbations. Planetary and satellite surfaces are different in composition than the near-Earth asteroids, which is in agreement with theoretical arguments that such bodies should not be sources. Some near-Earth asteroids supply portions of Earth's meteorite flux, but other sources must also contribute.

  8. Thermal infrared reflectance and emission spectroscopy of quartzofeldspathic glasses

    USGS Publications Warehouse

    Byrnes, J.M.; Ramsey, M.S.; King, P.L.; Lee, R.J.

    2007-01-01

    This investigation seeks to better understand the thermal infrared (TIR) spectral characteristics of naturally-occurring amorphous materials through laboratory synthesis and analysis of glasses. Because spectra of glass phases differ markedly from their mineral counterparts, examination of glasses is important to accurately determine the composition of amorphous surface materials using remote sensing datasets. Quantitatively characterizing TIR (5-25 ??m) spectral changes that accompany structural changes between glasses and mineral crystals provides the means to understand natural glasses on Earth and Mars. A suite of glasses with compositions analogous to common terrestrial volcanic glasses was created and analyzed using TIR reflectance and emission techniques. Documented spectral characteristics provide a basis for comparison with TIR spectra of other amorphous materials (glasses, clays, etc.). Our results provide the means to better detect and characterize glasses associated with terrestrial volcanoes, as well as contribute toward understanding the nature of amorphous silicates detected on Mars. Copyright 2007 by the American Geophysical Union.

  9. Analytical alignment tolerances for off-plane reflection grating spectroscopy

    NASA Astrophysics Data System (ADS)

    Allured, Ryan; McEntaffer, Randall T.

    2013-12-01

    Future NASA X-ray Observatories will shed light on a variety of high-energy astrophysical phenomena. Off-plane reflection gratings can be used to provide high throughput and spectral resolution in the 0.3-1.5 keV band, allowing for unprecedented diagnostics of energetic astrophysical processes. A grating spectrometer consists of multiple aligned gratings intersecting the converging beam of a Wolter-I telescope. Each grating will be aligned such that the diffracted spectra overlap at the focal plane. Misalignments will degrade both spectral resolution and effective area. In this paper we present an analytical formulation of alignment tolerances that define grating orientations in all six degrees of freedom. We verify our analytical results with raytrace simulations to fully explore the alignment parameter space. We also investigate the effect of misalignments on diffraction efficiency.

  10. Noninvasive particle sizing using camera-based diffuse reflectance spectroscopy.

    PubMed

    Abildgaard, Otto Højager Attermann; Frisvad, Jeppe Revall; Falster, Viggo; Parker, Alan; Christensen, Niels Jørgen; Dahl, Anders Bjorholm; Larsen, Rasmus

    2016-05-10

    Diffuse reflectance measurements are useful for noninvasive inspection of optical properties such as reduced scattering and absorption coefficients. Spectroscopic analysis of these optical properties can be used for particle sizing. Systems based on optical fiber probes are commonly employed, but their low spatial resolution limits their validity ranges for the coefficients. To cover a wider range of coefficients, we use camera-based spectroscopic oblique incidence reflectometry. We develop a noninvasive technique for acquisition of apparent particle size distributions based on this approach. Our technique is validated using stable oil-in-water emulsions with a wide range of known particle size distributions. We also measure the apparent particle size distributions of complex dairy products. These results show that our tool, in contrast to those based on fiber probes, can deal with a range of optical properties wide enough to track apparent particle size distributions in a typical industrial process. PMID:27168301

  11. Pronounced effects of additional resistance in Andreev reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, T. Y.; Huang, S. X.; Chien, C. L.

    2010-06-01

    We present a systematic investigation of the additional resistance (RE) , which is an unavoidable consequence of pseudo-four-probe electrical measurements, on the point-contact Andreev reflection (PCAR) spectrum by both modeling and experiments. Instead of considering the total resistance between the two voltage leads across a point contact as a sum of a contact resistance (RC) and a fixed sample resistance (RS) , it is essential to treat the total resistance as a sum of the Andreev resistance RAR and the additional resistance RE , which are, respectively, the resistances affected and unaffected by the Andreev reflection process. We show a detailed formalism of taking RE into account in modeling and demonstrate that the PCAR spectrum can be drastically affected by the presence of RE . Experimentally, we have found that not only RE cannot be readily measured or even estimated, it is in fact different for each contact, depending on the contact resistance and whether the contact is near the purely ballistic regime or the purely diffusive regime. A self-consistent process is necessary to analyze the entire PCAR spectrum, properly normalize the conductance, determine RE , and other parameters including the spin polarization and the superconducting gap for each contact. We determine RE for various contacts on specimens with different resistivity and resolve the causes of RE . For contacts close to the diffusive regime, there are two sources of RE : a dominant contribution which is linearly proportional to the total resistance and a constant value from the sample resistance. We also address the effects of additional resistance when PCAR is administered in the ballistic limit and in the diffusive limit. With the proper treatment of the additional resistance, we demonstrate that PCAR can quantitatively extract essential information of spin polarization and superconducting gap.

  12. Cryogenic Reflectance Spectroscopy in Support of Planetary Missions

    NASA Astrophysics Data System (ADS)

    Dalton, J. B.

    2002-11-01

    Present understanding of planetary composition is based primarily on remotely-sensed data, and in particular upon ultraviolet, visible, and infrared spectroscopy. Spectra acquired by telescopic and spacecraft instruments are compared to laboratory measurements of pure materials in order to identify surface components based on characteristic absorption features. Cryogenic spectral measurements are necessary for the study of worlds beyond the Earth's orbit. While some materials exhibit only small spectral changes as a function of temperature (Roush and Dalton 2002), many others are strongly temperature-dependent (Dalton and Clark 1998; Grundy and Schmitt 1998). For example, hydrated salts exhibit different spectral behavior under conditions appropriate to Europa (Dalton 2000) than at terrestrial temperatures (Crowley 1991) . The icy satellites of the outer solar system contain significant quantities of volatile ices (Roush 2001) which do not even exist at standard temperature and pressure (STP). A comprehensive spectral database of ices and minerals covering a wide temperature range will have applications ranging from the study of comets and Kniper Belt objects to outer planet satellites and the polar regions of Mars. Efforts are presently underway at NASA-Ames to develop capabilities which will contribute to such a database. As spacecraft instruments feature increasing spatial and spectral resolution, appropriate laboratory reference spectra become increasingly critical to accurate interpretation of the spacecraft data.

  13. Terahertz magneto-spectroscopy of a point contact based on CdTe/CdMgTe quantum well

    NASA Astrophysics Data System (ADS)

    Grigelionis, Ignas; Białek, Marcin; Grynberg, Marian; Czapkiewicz, Magdalena; Kolkovskiy, Valery; Wiater, Maciej; Wojciechowski, Tomasz; Wróbel, Jerzy; Wojtowicz, Tomasz; Diakonova, Nina; Knap, Wojciech; Łusakowski, Jerzy

    2015-01-01

    To understand a terahertz (THz) response of a point contact device, a number of samples based on CdTe/CdMgTe quantum wells grown by a molecular beam epitaxy were investigated at low temperatures and high magnetic fields. The experiments involved magneto-transport, photocurrent, and transmission measurements carried out with monochromatic THz sources or a Fourier spectrometer. Samples of different geometry with and without gate metallization were used. We observed excitations of a two-dimensional electron plasma in the form of optically induced Shubnikov-de Haas oscillations, cyclotron resonance transitions, and magneto-plasmon resonances. A polaron effect was observed at magnetic fields higher than 10 T. A point contact device processed with an electron beam lithography was investigated as a detector of THz radiation. It was shown that the main mechanism responsible for a THz performance of the point contact was excitation of magneto-plasmons with a wavevector defined by geometrical constrictions of the device mesa.

  14. Time-Domain Terahertz Spectroscopy (0.3 - 7.5 THz) of Molecular Ices of Simple Alcohols

    NASA Astrophysics Data System (ADS)

    McGuire, Brett A.; Ioppolo, Sergio; Allodi, Marco A.; de Vries, Xander; Finneran, Ian; Carroll, Brandon; Blake, Geoffrey

    2014-06-01

    We have recently constructed a time-domain TeraHertz (THz) spectrometer for the study of molecular ices in the far-infrared. Here, we present the results of a study of amorphous and crystalline ices of simple alcohols from methanol (CH_3OH) through butanol (CH_3(CH_2)_3OH) in the region of 0.3 - 7.5 THz. We examine the effects of the length and degree of branching of the carbon chain on the observed spectra arising from the bulk, large-amplitude motions which are prominent in this spectral region. We also discuss these results in an astrochemical context: the application of these spectra to astronomical observations of interstellar ices with Herschel PACS/SPIRE and SOFIA.

  15. Phase-resolved reflectance spectroscopy on layered turbid media

    NASA Astrophysics Data System (ADS)

    Hielscher, Andreas H.; Liu, Hanli; Chance, Britton; Tittel, Frank K.; Jacques, Steven L.

    1995-05-01

    In this study, we investigate the influence of layered tissue structures on the phase-resolved reflectance. As a particular example, we consider the affect of the skin, skull, and meninges on noninvasive blood oxygenation determination of the brain. In this case, it's important to know how accurate one can measure the absorption coefficient of the brain through the enclosing layers of different tissues. Experiments were performed on layered gelatin tissue phantoms and the results compared to diffusion theory. It is shown that when a high absorbing medium is placed on top of a low absorbing medium, the absorption coefficient of the lower layer is accessible. In the inverse case, where a low absorbing medium is placed on top of a high absorbing medium, the absorption coefficient of the underlying medium can only be determined if the differences in the absorption coefficient are small, or the top layer is very thin. Investigations on almost absorption and scattering free layers, like the cerebral fluid filled arachnoid, reveal that the determination of the absorption coefficient is barely affected by these kinds of structures.

  16. Mars surface composition from reflectance spectroscopy - A summary

    NASA Technical Reports Server (NTRS)

    Singer, R. B.; Clark, R. N.; Mccord, T. B.; Adams, J. B.; Huguenin, R. L.

    1979-01-01

    Visible and near-infrared reflectance spectra and multispectral maps of the Martian surface are discussed, and implications of the data for the composition of the Martian surface are considered. Spacecraft and earth-based telescopic observations have confirmed the generally bimodal albedo distribution of the planet, dividing the surface into bright and dark regions. Mars spectra are characterized by the presence of strong Fe(+3) absorption, which is attributed to various ferric oxide minerals. Interpretations of the spectra from the dark regions indicate a basaltic or ultramafic source rock. Evidence for water ice or a highly desiccated metal hydrate has been obtained, along with evidence for CO2-ice only in the south polar cap. Mariner 9 observations of Martian dust suggest the presence of rather acidic rock or mineral particles, or a montmorillonite-type clay. Prospects for the future study of Martian surface composition include continuing earth-based spectrophotometric studies, and high-spectral-resolution mapping of a significant portion of the surface by the Galileo spacecraft and the next Mars mission.

  17. High volume confinement in two-photon total-internal-reflection fluorescence correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Ivanov, D.; Shcheslavskiy, V.; Märki, I.; Leutenegger, M.; Lasser, T.

    2009-02-01

    We report results on two-photon total-internal-reflection fluorescence correlation spectroscopy with radially polarized light. The combination of liquid crystal spatial light modulator, providing radial polarization with ultrafast laser (picosecond Nd:GdVO4 laser), allowed us to take the advantage of nonlinear optical contrast mechanisms to suppress the side-lobe energy specific for radial polarization and reduce the effective excited volume twice compared to one-photon evanescent wave excitation in fluorescence correlation spectroscopy.

  18. Terahertz Spectroscopy and Global Analysis of the Bending Vibrations of ^{12}C_2H_2 and ^{12}C_2D_2

    NASA Astrophysics Data System (ADS)

    Yu, Shanshan; Drouin, Brian J.; Pearson, John C.; Pickett, Herbert M.; Lattanzi, Valerio; Walters, Adam

    2009-06-01

    Symmetric molecules have no permanent dipole moment and are undetectable by rotational spectroscopy. Their interstellar observations have previously been limited to mid-infrared vibration-rotation spectroscopy. Although relatively weak, vibrational difference bands provide a means for detection of non polar molecules by terahertz techniques with microwave precision. Herschel, SOFIA, and ALMA have the potential to identify a number of difference bands of light symmetric species, e.g., C_2H_2, CH_4 and C_3. This paper reports the results of the laboratory study on ^{12}C_2H_2 and ^{12}C_2D_2. The symmetric isotopomers of acetylene have two bending modes, the trans bending ν_4 (^1{π}_g), and the cis bending ν_5 (^1{π}_u). For ^{12}C_2H_2, the two bending modes occur at 612 and 729 cm^{-1}, respectively. For ^{12}C_2D_2, the two bending modes occur at 511 and 538 cm^{-1}. The ν_5-ν_4 difference bands are allowed and occur in the microwave, terahertz, and far-infrared wavelengths, with band origins at 117 cm^{-1} (3500 GHz) for ^{12}C_2H_2 and 27 cm^{-1} (900 GHz) for ^{12}C_2D_2. Two hundred and fifty-one ^{12}C_2D_2 transitions, which are from ν_5-ν_4, (ν_5+ν_4)-2ν_4 and 2ν_5-(ν_5+ν_4) bands, have been measured in the 0.2-1.6 THz region, and 202 of them were observed for the first time. The precision of these measurements is estimated to be from 50 kHz to 100 kHz. A multistate analysis was carried out for the bending vibrational modes ν_4 and ν_5 of ^{12}C_2D_2, which includes the lines observed in this work and prior microwave, far-infrared and infrared data on the pure bending levels. Significantly improved molecular parameters were obtained for ^{12}C_2D_2 by adding the new measurements to the old data set which had only 10 lines with microwave measurement precision. The experiments on ^{12}C_2H_2 are in progress and ten P branch lines have been observed. We will present the ^{12}C_2H_2 results to date.

  19. In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Bertram, F.; Zhang, F.; Evertsson, J.; Carlà, F.; Pan, J.; Messing, M. E.; Mikkelsen, A.; Nilsson, J.-O.; Lundgren, E.

    2014-07-01

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  20. In situ anodization of aluminum surfaces studied by x-ray reflectivity and electrochemical impedance spectroscopy

    SciTech Connect

    Bertram, F. Evertsson, J.; Messing, M. E.; Mikkelsen, A.; Lundgren, E.; Zhang, F.; Pan, J.; Carlà, F.; Nilsson, J.-O.

    2014-07-21

    We present results from the anodization of an aluminum single crystal [Al(111)] and an aluminum alloy [Al 6060] studied by in situ x-ray reflectivity, in situ electrochemical impedance spectroscopy and ex situ scanning electron microscopy. For both samples, a linear increase of oxide film thickness with increasing anodization voltage was found. However, the slope is much higher in the single crystal case, and the break-up of the oxide film grown on the alloy occurs at a lower anodization potential than on the single crystal. The reasons for these observations are discussed as are the measured differences observed for x-ray reflectivity and electrochemical impedance spectroscopy.

  1. In vivo soft tissue differentiation by diffuse reflectance spectroscopy: preliminary results

    NASA Astrophysics Data System (ADS)

    Zam, Azhar; Stelzle, Florian; Tangermann-Gerk, Katja; Adler, Werner; Nkenke, Emeka; Neukam, Friedrich Wilhelm; Schmidt, Michael; Douplik, Alexandre

    Remote laser surgery does not provide haptic feedback to operate layer by layer and preserve vulnerable anatomical structures like nerve tissue or blood vessels. The aim of this study is identification of soft tissue in vivo by diffuse reflectance spectroscopy to set the base for a feedback control system to enhance nerve preservation in oral and maxillofacial laser surgery. Various soft tissues can be identified by diffuse reflectance spectroscopy in vivo. The results may set the base for a feedback system to prevent nerve damage during oral and maxillofacial laser surgery.

  2. [Application of near-infrared diffuse reflectance spectroscopy to the detection and identification of transgenic corn].

    PubMed

    Rui, Yu-kui; Luo, Yun-bo; Huang, Kun-lun; Wang, Wei-min; Zhang, Lu-da

    2005-10-01

    With the rapid development of the GMO, more and more GMO food has been pouring into the market. Much attention has been paid to GMO labeling under the controversy of GMO safety. Transgenic corns and their parents were scanned by continuous wave of near infrared diffuse reflectance spectroscopy range of 12000-4000 cm(-1); the resolution was 4 cm(-1); scanning was carried out for 64 times; BP algorithm was applied for data processing. The GMO food was easily resolved. Near-infrared diffuse reflectance spectroscopy is unpolluted and inexpensive compared with PCR and ELISA, so it is a very promising detection method for GMO food.

  3. Phonon Mode Transformation Across the Orthohombic-Tetragonal Phase Transition in a Lead Iodide Perovskite CH3NH3PbI3: A Terahertz Time-Domain Spectroscopy Approach.

    PubMed

    La-o-Vorakiat, Chan; Xia, Huanxin; Kadro, Jeannette; Salim, Teddy; Zhao, Daming; Ahmed, Towfiq; Lam, Yeng Ming; Zhu, Jian-Xin; Marcus, Rudolph A; Michel-Beyerle, Maria-Elisabeth; Chia, Elbert E M

    2016-01-01

    We study the temperature-dependent phonon modes of the organometallic lead iodide perovskite CH3NH3PbI3 thin film across the terahertz (0.5-3 THz) and temperature (20-300 K) ranges. These modes are related to the vibration of the Pb-I bonds. We found that two phonon modes in the tetragonal phase at room temperature split into four modes in the low-temperature orthorhombic phase. By use of the Lorentz model fitting, we analyze the critical behavior of this phase transition. The carrier mobility values calculated from the low-temperature phonon mode frequencies, via two theoretical approaches, are found to agree reasonably with the experimental value (∼2000 cm(2) V(-1) s(-1)) from a previous time-resolved THz spectroscopy work. Thus, we have established a possible link between terahertz phonon modes and the transport properties of perovskite-based solar cells. PMID:26633131

  4. Phonon Mode Transformation across the Orthohombic-Tetragonal Phase Transition in a Lead-Iodide Perovskite CH3NH3PbI3: a Terahertz Time-Domain Spectroscopy Approach

    NASA Astrophysics Data System (ADS)

    Chia, Elbert E. M.; La-O-Vorakiat, Chan; Kadro, Jeannette; Salim, Teddy; Zhao, Daming; Ahmed, Towfiq; Lam, Yeng Ming; Zhu, Jian-Xin; Marcus, Rudolph; Michel-Beyerle, Maria-Elisabeth

    Using terahertz time-domain spectroscopy (THz-TDS), we study the temperature-dependent phonon modes of the organometallic lead iodide perovskite CH3NH3PbI3 thin film across the terahertz (0.5-3 THz) and temperature (20-300 K) ranges. These modes are related to the vibration of the Pb-I bonds. We found that two phonon modes in the tetragonal phase at room temperature split into four modes in the low-temperature orthorhombic phase. By use of the Lorentz model fitting, we analyze the critical behavior of this phase transition. King Mongkut's University of Technology Thonburi (Grant No. SCI58-003), Singapore MOE Tier 1 (RG13/12, RG123/14), ONR, ARO, NTU Biophysics Center, LANL LDRD, LANL CINT.

  5. Synthesis, structure, terahertz spectroscopy and luminescent properties of copper (I) complexes with bis(diphenylphosphino)methane and N-donor ligands

    NASA Astrophysics Data System (ADS)

    Fan, Wei-Wei; Li, Zhong-Feng; Li, Jiao-Bao; Yang, Yu-Ping; Yuan, Yuan; Tang, Han-Qin; Gao, Ling-Xiao; Jin, Qiong-Hua; Zhang, Zhen-Wei; Zhang, Cun-Lin

    2015-11-01

    The reactions of copper(I) salts CuX [X = Cl, OTf (OTf = CF3SO3) and ClO4] and bis(diphenylphosphino)methane (dppm) with 4,4-bipyridine (4,4-bipy), 2,2-bipyridine (2,2-bipy), isoquinoline (i-C9H7N) and 1,10-phenanthroline (phen) lead to five new copper(I) complexes: [CuCl(dppm)(i-C9H7N)]2 (1), {[CuCl(dppm)(phen)]2•5H2O}n (2), [Cu2Cl2(dppm)2(4,4-bipy)]•4CH3CN (3), [Cu(dppm)(2,2-bipy)]2(OTf)2 (4), {[Cu2Cl(dppm)2(4,4-bipy)](ClO4)}n (5). Complexes 1, 3 and 4 are of dinuclear structure with eight-membered Cu2P4C2 rings. The structure of compound 2 can be simplified as three-dimensional topology. Complex 5 is of infinite chain structure linked by 4,4-bipy. All these complexes are characterized by IR, elemental analyses, single-crystal X-ray diffraction analysis, luminescence, NMR and terahertz time-domain spectroscopy.

  6. Estimation of Crystallinity of Nifedipine-Polyvinylpyrrolidone Solid Dispersion by Usage of Terahertz Time-Domain Spectroscopy and of X-Ray Powder Diffractometer.

    PubMed

    Takeuchi, Issei; Shimakura, Kemmaro; Kuroda, Hideki; Nakajima, Takehisa; Goto, Satoru; Makino, Kimiko

    2015-12-01

    Crystalline state of pharmaceutical materials is of great importance in preparation of pharmaceutics, because their physicochemical properties affect bioavailability, quality of products, therapeutic level and manufacturing process. In this study, we have estimated time-dependent changes of nifedipine in nifedipine-polyvinylpyrrolidone (PVP) solid dispersion by measuring terahertz time-domain spectroscopy (THz-TDS) and by X-ray powder diffractometry (XRPD), and compared their correlativity. Crystallinity of nifedipine-PVP solid dispersion was changed by storing the amorphous sample at 25°C-75°C and relative humidity of over 80% for 0.25-24.00 h. To compare the results of two types of measurements, we have used a general method of linear regression analysis. Crystallinities estimated using THz-TDS were plotted on the x-axis and that of XRPD were on the y-axis. From the result of the calculation, the correlativity of them was confirmed. THz-TDS has the capability of becoming the replacement of XRPD.

  7. Measurement of Trans-Fatty Acids in Cereal Products Without Oil Extraction Using NIR Reflectance Spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Near infrared (NIR) reflectance spectroscopy was evaluated as a rapid technique, to determine the trans-fatty acid content of ground cereal products. NIR spectra were obtained with a dispersive spectrometer and trans-fatty acids determined by modified AOAC Method 996.01. First derivative PLS1 mode...

  8. Absorption and Scattering Coefficients: A Biophysical-Chemistry Experiment Using Reflectance Spectroscopy

    ERIC Educational Resources Information Center

    Cordon, Gabriela B.; Lagorio, M. Gabriela

    2007-01-01

    A biophysical-chemistry experiment, based on the reflectance spectroscopy for calculating the absorption and scattering coefficients of leaves is described. The results show that different plants species exhibit different values for both the coefficients because of their different pigment composition.

  9. Prediction of olive quality using FT-NIR spectroscopy in reflectance and transmittance modes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to use FT-NIR spectroscopy to predict the firmness, oil content and color of two olive (Olea europaea L) varieties (‘Ayvalik’ and ‘Gemlik’). Spectral measurements were performed on the intact olives for the wavelengths of 780-2500 nm in reflectance and for 800-1725...

  10. Diffuse Reflectance Spectroscopy of Human Skin Using a Commercial Fiber Optic Spectrometer

    SciTech Connect

    Atencio, J. A. Delgado; Rodriguez, M. Cunill; Montiel, S. Vazquez y; Castro, Jorge; Rodriguez, A. Cornejo; Gutierrez, J. L.; Martinez, F.; Gutierrez, B.; Orozco, E.

    2008-08-11

    Diffuse reflectance spectroscopy is a reliable and easy to implement technique in human tissue characterization. In this work we evaluate the performance of the commercial USB4000 miniature fiber optic spectrometer in the in-vivo measurement of the diffuse reflectance spectra of different healthy skin sites and lesions in a population of 54 volunteers. Results show, that this spectrometer reproduces well the typical signatures of skin spectra over the 400-1000 nm region. Remarkable spectral differences exist between lesions and normal surrounding skin. A diffusion-based model was used to simulate reflectance spectra collected by the optical probe of the system.

  11. Terahertz Technology: A Boon to Tablet Analysis

    PubMed Central

    Wagh, M. P.; Sonawane, Y. H.; Joshi, O. U.

    2009-01-01

    The terahertz gap has a frequency ranges from ∼0.3 THz to ∼10 THz in the electromagnetic spectrum which is in between microwave and infrared. The terahertz radiations are invisible to naked eye. In comparison with x-ray they are intrinsically safe, non-destructive and non-invasive. Terahertz spectroscopy enables 3D imaging of structures and materials, and the measurement of the unique spectral fingerprints of chemical and physical forms. Terahertz radiations are produced by a dendrimer based high power terahertz source and spectroscopy technologies. It resolves many of the questions left unanswered by complementary techniques, such as optical imaging, Raman and infrared spectra. In the pharmaceutical industries it enables nondestructive, internal, chemical analysis of tablets, capsules, and other dosage forms. Tablet coatings are a major factor in drug bioavailability. Therefore tablet coatings integrity and uniformity are of crucial importance to quality. Terahertz imaging gives an unparalleled certainty about the integrity of tablet coatings and the matrix performance of tablet cores. This article demonstrates the potential of terahertz pulse imaging for the analysis of tablet coating thickness by illustrating the technique on tablets. PMID:20490288

  12. Design and Signature Analysis of Remote Trace-Gas Identification Methodology Based on Infrared-Terahertz Double-Resonance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Tanner, Elizabeth A.; Phillips, Dane J.; Persons, Christopher M.; De Lucia, Frank C.; Everitt, Henry O.

    2014-11-01

    The practicality of a newly proposed infrared-terahertz (IR-THz) double-resonance (DR) spectroscopic technique for remote trace-gas identification is explored. The strength of the DR signatures depends on known molecular parameters from which a combination of pump-probe transitions may be identified to recognize a specific analyte. Atmospheric pressure broadening of the IR and THz trace-gas spectra relaxes the stringent pump coincidence requirement, allowing many DR signatures to be excited, some of which occur in the favorable atmospheric transmission windows below 500 GHz. By designing the DR spectrometer and performing a detailed signal analysis, the pump-probe power requirements for detecting trace amounts of methyl fluoride, methyl chloride, or methyl bromide may be estimated for distances up to 1 km. The strength of the DR signature increases linearly with pump intensity but only as the square root of the probe power because the received signal is in the Townes noise limit. The concept of a specificity matrix is introduced and used to quantify the recognition specificity and calculate the probability of false positive detection of an interferent.

  13. Terahertz antireflection coatings using metamaterials

    SciTech Connect

    Chen, Hou-tong; Zhou, Jiangfeng; O' Hara, John F; Azad, Abul K; Chen, Frank; Taylor, Antoinette J

    2010-01-01

    We demonstrate terahertz metamaterial antireflection coatings (ARCs) that significantly reduce the reflection and enhance the transmission at an interface of dielectric media. They are able to operate over a wide range of incidence angles for both TM and TE polarizations. Experiments and finite-element simulations will be presented and discussed.

  14. Terahertz optical properties of the cornea

    NASA Astrophysics Data System (ADS)

    Liu, Wen-Quan; Lu, Yuan-Fu; Jiao, Guo-Hua; Chen, Xian-Feng; Li, Jin-Ying; Chen, Si-Hai; Dong, Yu-Ming; Lv, Jian-Cheng

    2016-01-01

    We present a study aimed at developing a terahertz time domain spectroscopy (THz-TDS) system for detection of the optical properties of ex vivo rabbit corneal tissues with different water content at terahertz frequencies (0.1-0.3 THz). The refractive index decreased with frequency while the absorption coefficient increased with frequency. Our experimental results matched the theoretical calculation very well revealing that both the absorption coefficient and the refractive index of a hydrated cornea were much larger than that of a dehydrated cornea and the terahertz properties depended on the hydrate conditions of the biosamples.

  15. Elastomeric silicone substrates for terahertz fishnet metamaterials

    NASA Astrophysics Data System (ADS)

    Khodasevych, I. E.; Shah, C. M.; Sriram, S.; Bhaskaran, M.; Withayachumnankul, W.; Ung, B. S. Y.; Lin, H.; Rowe, W. S. T.; Abbott, D.; Mitchell, A.

    2012-02-01

    In this work, we characterize the electromagnetic properties of polydimethylsiloxane (PDMS) and use this as a free-standing substrate for the realization of flexible fishnet metamaterials at terahertz frequencies. Across the 0.2-2.5 THz band, the refractive index and absorption coefficient of PDMS are estimated as 1.55 and 0-22 cm-1, respectively. Electromagnetic modeling, multi-layer flexible electronics microfabrication, and terahertz time-domain spectroscopy are used in the design, fabrication, and characterization of the metamaterials, respectively. The properties of PDMS add a degree of freedom to terahertz metamaterials, with the potential for tuning by elastic deformation or integrated microfluidics.

  16. In vivo detection of epileptic brain tissue using static fluorescence and diffuse reflectance spectroscopy.

    PubMed

    Yadav, Nitin; Bhatia, Sanjiv; Ragheb, John; Mehta, Rupal; Jayakar, Prasanna; Yong, William; Lin, Wei-Chiang

    2013-02-01

    Diffuse reflectance and fluorescence spectroscopy are used to detect histopathological abnormalities of an epileptic brain in a human subject study. Static diffuse reflectance and fluorescence spectra are acquired from normal and epileptic brain areas, defined by electrocorticography (ECoG), from pediatric patients undergoing epilepsy surgery. Biopsy specimens are taken from the investigated sites within an abnormal brain. Spectral analysis reveals significant differences in diffuse reflectance spectra and the ratio of fluorescence and diffuse reflectance spectra from normal and epileptic brain areas defined by ECoG and histology. Using these spectral differences, tissue classification models with accuracy above 80% are developed based on linear discriminant analysis. The differences between the diffuse reflectance spectra from the normal and epileptic brain areas observed in this study are attributed to alterations in the static hemodynamic characteristics of an epileptic brain, suggesting a unique association between the histopathological and the hemodynamic abnormalities in an epileptic brain.

  17. In vivo detection of epileptic brain tissue using static fluorescence and diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Yadav, Nitin; Bhatia, Sanjiv; Ragheb, John; Mehta, Rupal; Jayakar, Prasanna; Yong, William; Lin, Wei-Chiang

    2013-02-01

    Diffuse reflectance and fluorescence spectroscopy are used to detect histopathological abnormalities of an epileptic brain in a human subject study. Static diffuse reflectance and fluorescence spectra are acquired from normal and epileptic brain areas, defined by electrocorticography (ECoG), from pediatric patients undergoing epilepsy surgery. Biopsy specimens are taken from the investigated sites within an abnormal brain. Spectral analysis reveals significant differences in diffuse reflectance spectra and the ratio of fluorescence and diffuse reflectance spectra from normal and epileptic brain areas defined by ECoG and histology. Using these spectral differences, tissue classification models with accuracy above 80% are developed based on linear discriminant analysis. The differences between the diffuse reflectance spectra from the normal and epileptic brain areas observed in this study are attributed to alterations in the static hemodynamic characteristics of an epileptic brain, suggesting a unique association between the histopathological and the hemodynamic abnormalities in an epileptic brain.

  18. Wall reflection modeling for charge exchange recombination spectroscopy (CXRS) measurements on Textor and ITER

    NASA Astrophysics Data System (ADS)

    Banerjee, Santanu; Vasu, P.; von Hellermann, M.; Jaspers, R. J. E.

    2010-12-01

    Contamination of optical signals by reflections from the tokamak vessel wall is a matter of great concern. For machines such as ITER and future reactors, where the vessel wall will be predominantly metallic, this is potentially a risk factor for quantitative optical emission spectroscopy. This is, in particular, the case when bremsstrahlung continuum radiation from the bulk plasma is used as a common reference light source for the cross-calibration of visible spectroscopy. In this paper the reflected contribution to the continuum level in Textor and ITER has been estimated for the detection channels meant for charge exchange recombination spectroscopy (CXRS). A model assuming diffuse reflection has been developed for the bremsstrahlung which is a much extended source. Based on this model, it is shown that in the case of ITER upper port 3, a wall with a moderate reflectivity of 20% leads to the wall reflected fraction being as high as 55-60% of the weak signals in the edge channels. In contrast, a complete bidirectional reflectance distribution function (BRDF) based model has been developed in order to estimate the reflections from more localized sources like the charge exchange (CX) emission from a neutral beam in tokamaks. The largest signal contamination of ~15% is seen in the core CX channels, where the true CX signal level is much lower than that in the edge channels. Similar values are obtained for Textor also. These results indicate that the contributions from wall reflections may be large enough to significantly distort the overall spectral features of CX data, warranting an analysis at different wavelengths.

  19. [Comparison of FTIR microspectroscopy and diffuse reflectance spectroscopy for monitor of solid phase reaction].

    PubMed

    Wu, Q; Yang, S; Luo, J; Huang, W

    2000-10-01

    17 FTIR micro transmission spectra of single resin beads of each sample, from polystyrene sulfonyl chloride resin changing to polystyrene sulfonyl amide resin in solid-phase reaction in water at 0 degree C, 20 degrees C, 40 degrees C, 60 degrees C, were recorded. The reaction was monitored by the means of FTIR microspectroscopy and diffuse reflectance spectroscopy upon the products. It was showed that the pressed single bead as a piece of biscuit was able to give higher quality spectrum. In comparison, 8 diffuse reflectance spectra of each sample were also collected. It seems that the diffuse reflectance spectroscopy is a more easy dealing with and effective method to control the whole reaction. However, the microspectroscopy is the first choice to check the difference between resin beads.

  20. Active terahertz metamaterials

    SciTech Connect

    Chen, Hou-tong; O' Hara, John F; Taylor, Antoinette J

    2009-01-01

    In this paper we present an overview of research in our group in terahertz (THz) metamaterials and their applications. We have developed a series of planar metamaterials operating at THz frequencies, all of which exhibit a strong resonant response. By incorporating natural materials, e.g. semiconductors, as the substrates or as critical regions of metamaterial elements, we are able to effectively control the metamaterial resonance by the application of external stimuli, e.g., photoexcitation and electrical bias. Such actively controllable metamaterials provide novel functionalities for solid-state device applications with unprecedented performance, such as THz spectroscopy, imaging, and many others.

  1. [The research progress in determining lignocellulosic content by near infrared reflectance spectroscopy technology].

    PubMed

    Du, Juan; An, Dong; Xia, Tian; Huang, Yan-Hua; Li, Hong-Chao; Zhang, Yun-Wei

    2013-12-01

    Near infrared reflectance spectroscopy technology, as a new analytic method, can be used to determine the content of lignin, cellulose and hemi-cellulose which is faster, effective, easier to operate, and more accurate than the traditional wet chemical methods. Nowadays it has been widely used in measuring the composition of lignocelluloses in woody plant and herbaceous plant. The domestic and foreign research progress in determining the lignin, cellulose and hemi-cellulose content in woody plant ( wood and bamboo used as papermaking raw materials and wood served as potential biomass energy) and herbaceous plant (forage grass and energy grass) by near infrared reflectance spectroscopy technology is comprehensively summarized and the advances in method studies of measuring the composition of lignocelluloses by near infrared reflectance spectroscopy technology are summed up in three aspects, sample preparation, spectral data pretreatment and wavelength selection methods, and chemometric analysis respectively. Four outlooks are proposed combining the development statues of wood, forage grass and energy grass industry. First of all, the authors need to establish more feasible and applicable models for a variety of uses which can be used for more species from different areas, periods and anatomical parts. Secondly, comprehensive near infrared reflectance spectroscopy data base of grass products quality index needs to be improved to realize on-line quality and process control in grassproducts industry, which can guarantee the quality of the grass product. Thirdly, the near infrared reflectance spectroscopy quality index model of energy plant need to be built which can not only contribute to breed screening, but also improve the development of biomass industry. Besides, modeling approaches are required to be explored and perfected any further. Finally, the authors need to try our best to boost the advancement in the determination method of lignin, cellulose and hemi

  2. Ultra-broadband terahertz time-domain ellipsometric spectroscopy utilizing GaP and GaSe emitters and an epitaxial layer transferred photoconductive detector

    SciTech Connect

    Yamashita, Masatsugu Takahashi, Hideki; Otani, Chiko; Ouchi, Toshihiko

    2014-02-03

    We present a reflection-type ultra-broadband terahertz (THz) time-domain spectroscopic ellipsometry system covering the frequency range of 0.5–30 THz. GaP (110) and z-cut GaSe crystals are used as emitters to generate the THz and mid-infrared pulses, respectively, and a photoconductive antenna switch using a low-temperature grown GaAs epitaxial layer transferred on Si substrate was used as a detector. By changing the emitter between the GaP and GaSe crystals, the measurable frequency range can be easily switched from the 0.5–7.8 THz range to the 7.8–30 THz range without additional optical alignment. We demonstrated the measurement of the dielectric function in a p-type InAs wafer and the optical conductivity of an indium tin oxide (ITO) thin film. The obtained carrier density and the mobility of the ITO thin film show good agreement with that obtained by the Hall measurement.

  3. Sub-terahertz spectroscopy reveals that proteins influence the properties of water at greater distances than previously detected

    SciTech Connect

    Sushko, Oleksandr; Dubrovka, Rostyslav; Donnan, Robert S.

    2015-02-07

    The initial purpose of the study is to systematically investigate the solvation properties of different proteins in water solution by terahertz (THz) radiation absorption. Transmission measurements of protein water solutions have been performed using a vector network analyser-driven quasi-optical bench covering the WR-3 waveguide band (0.220–0.325 THz). The following proteins, ranging from low to high molecular weight, were chosen for this study: lysozyme, myoglobin, and bovine serum albumin (BSA). Absorption properties of solutions were studied at different concentrations of proteins ranging from 2 to 100 mg/ml. The concentration-dependent absorption of protein molecules was determined by treating the solution as a two-component model first; then, based on protein absorptivity, the extent of the hydration shell is estimated. Protein molecules are shown to possess a concentration-dependent absorptivity in water solutions. Absorption curves of all three proteins sharply peak towards a dilution-limit that is attributed to the enhanced flexibility of protein and amino acid side chains. An alternative approach to the determination of hydration shell thickness is thereby suggested, based on protein absorptivity. The proposed approach is independent of the absorption of the hydration shell. The derived estimate of hydration shell thickness for each protein supports previous findings that protein-water interaction dynamics extends beyond 2-3 water solvation-layers as predicted by molecular dynamics simulations and other techniques such as NMR, X-ray scattering, and neutron scattering. According to our estimations, the radius of the dynamic hydration shell is 16, 19, and 25 Å, respectively, for lysozyme, myoglobin, and BSA proteins and correlates with the dipole moment of the protein. It is also seen that THz radiation can serve as an initial estimate of the protein hydrophobicity.

  4. Terahertz and far-infrared synchrotron spectroscopy and global modeling of methyl mercaptan, CH3(32)SH.

    PubMed

    Xu, Li-Hong; Lees, R M; Crabbe, G T; Myshrall, J A; Müller, H S P; Endres, C P; Baum, O; Lewen, F; Schlemmer, S; Menten, K M; Billinghurst, B E

    2012-09-14

    In this work, terahertz and Fourier transform far-infrared (FTFIR) synchrotron spectra of methyl mercaptan, CH(3)SH, have been investigated in order to provide new laboratory information for enhanced observations of this species in interstellar molecular clouds and star-forming regions. Like its methanol cousin, methyl mercaptan has particularly rich spectra associated with its large-amplitude internal rotation that extend throughout the THz and FIR regions. We have recorded new spectra for CH(3)SH from 1.1-1.5 and 1.790-1.808 THz at the University of Cologne as well as high-resolution FTFIR synchrotron spectra from 50-550 cm(-1) at 0.001 cm(-1) resolution on the far-IR beam-line at the Canadian Light Source. Assignments are reported for rotational quantum numbers up to J ≈ 40 and K ≈ 15, and torsional states up to v(t) = 2 for the THz measurements and v(t) = 3 for the FTFIR observations. The THz and FTFIR measurements together with literature results have been combined in a global analysis of a dataset comprising a total of 1725 microwave and THz frequencies together with ~18000 FTFIR transitions, ranging up to v(t) = 2 and J(max) = 30 for MW∕THz and 40 for FTFIR. The global fit employs 78 torsion-rotation parameters and has achieved a weighted standard deviation of ~1.1. A prediction list (v(t) ≤ 2, J ≤ 45 and K ≤ 20) has been generated from the model giving essentially complete coverage of observable CH(3)(32)SH transitions within the bandwidths of major new astronomical facilities such as HIFI (Heterodyne Instrument for the Far Infrared) on the Herschel Space Observatory, ALMA (Atacama Large Millimeter Array), SOFIA (Stratospheric Observatory For Infrared Astronomy) and APEX (Atacama Pathfinder Experiment) to close to spectroscopic accuracy.

  5. Scanning Terahertz Heterodyne Imaging Systems

    NASA Technical Reports Server (NTRS)

    Siegel, Peter; Dengler, Robert

    2007-01-01

    Scanning terahertz heterodyne imaging systems are now at an early stage of development. In a basic scanning terahertz heterodyne imaging system, (see Figure 1) two far-infrared lasers generate beams denoted the local-oscillator (LO) and signal that differ in frequency by an amount, denoted the intermediate frequency (IF), chosen to suit the application. The LO beam is sent directly to a mixer as one of two inputs. The signal beam is focused to a spot on or in the specimen. After transmission through or reflection from the specimen, the beams are focused to a spot on a terahertz mixer, which extracts the IF outputs. The specimen is mounted on a translation stage, by means of which the focal spot is scanned across the specimen to build up an image.

  6. Terahertz radar cross section measurements.

    PubMed

    Iwaszczuk, Krzysztof; Heiselberg, Henning; Jepsen, Peter Uhd

    2010-12-01

    We perform angle- and frequency-resolved radar cross section (RCS) measurements on objects at terahertz frequencies. Our RCS measurements are performed on a scale model aircraft of size 5-10 cm in polar and azimuthal configurations, and correspond closely to RCS measurements with conventional radar on full-size objects. The measurements are performed in a terahertz time-domain system with freely propagating terahertz pulses generated by tilted pulse front excitation of lithium niobate crystals and measured with sub-picosecond time resolution. The application of a time domain system provides ranging information and also allows for identification of scattering points such as weaponry attached to the aircraft. The shapes of the models and positions of reflecting parts are retrieved by the filtered back projection algorithm.

  7. Reflectance spectroscopy of palagonite and iron-rich montmorillonite clay mixtures: Implications for the surface composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, J. B.; Handy, J.

    1991-01-01

    Because of the power of remote sensing reflectance spectroscopy in determining mineralogy, it was used as the major method of identifying possible mineral analogs of the Martian surface. A summary of proposed Martian surface compositions from reflectance spectroscopy before 1979 was presented. Since that time, iron-rich montmorillonite clay, nanocrystalline or nanophase hematite, and palagonite were suggested as Mars soil analog materials.

  8. [Sugar characterization of mini-watermelon and rapid sugar determination by near infrared diffuse reflectance spectroscopy].

    PubMed

    Wang, Shuo; Yuan, Hong-fu; Song, Chun-feng; Xie, Jin-chun; Li, Xiao-yu; Feng, Le-ping

    2012-08-01

    In the present paper, the distribution of sugar level within the mini-watermelon was studied, a new sugar characterization method of mini-watermelon using average sugar level, the highest sugar level and the lowest sugar level index is proposed. Feasibility of nondestructive determination of mini-watermenlon sugar level using diffuse reflectance spectroscopy information was investigated by an experiment. PLS models for measuring the 3 sugar levels were established. The results obtained by near infrared spectroscopy agreed with that of the new method established above.

  9. Infrared reflection-absorption spectroscopy of hyperfine layers on surfaces of semiconductors and dielectrics

    NASA Astrophysics Data System (ADS)

    Gruzinov, S. N.; Tolstoy, V. P.

    1988-02-01

    Infrared reflection-absorption spectroscopy of film son surfaces of transparent or weakly absorbing semiconductor and dielectric substrates is analyzed theoretically, the purpose being to establish the conditions for maximum sensitivity of this method. The absorption factor, namely the relative change of the reflection coefficient upon formation of a film on the substrate surface, is selected as the sensitivity criterion. The analysis is based on exact relations, one for a homogeneous isotopic absorbing film between substrate and ambient medium with plane-parallel boundaries and one for a reflecting layer with the possibility of multiple reflections taken into account. Calculations have been programmed on a computer for up to 60 nm thick SiO2 films on various substrates and infrared radiation within the 8 to 11 gmm waveband. The results indicate that the dependence of the absorption factor on the radiation wavelength and on the film thickness is different with the radiation s-polarized than with the radiation p-polarized. Calculations have also yielded the dispersion of optical constants characterizing a SiO2 film. According to these results, infrared spectroscopy is most sensitive to films on substrates with a small refractive index and when done with p-polarized radiation incident at exactly or approximately the Brewster angle for a determination of their presence and their composition respectively, also when no multiple reflections occur.

  10. Diagnostics of pigmented skin tumors based on laser-induced autofluorescence and diffuse reflectance spectroscopy

    SciTech Connect

    Borisova, E; Avramov, L; Troyanova, P; Pavlova, P

    2008-06-30

    Results of investigation of cutaneous benign and malignant pigmented lesions by laser-induced autofluorescence spectroscopy (LIAFS) and diffuse reflectance spectroscopy (DRS) are presented. The autofluorescence of human skin was excited by a 337-nm nitrogen laser. A broadband halogen lamp (400-900 nm) was used for diffuse reflectance measurements. A microspectrometer detected in vivo the fluorescence and reflectance signals from human skin. The main spectral features of benign (dermal nevi, compound nevi, dysplastic nevi) and malignant (melanoma) lesions are discussed. The combined usage of the fluorescence and reflectance spectral methods to determine the type of the lesion, which increases the total diagnostic accuracy, is compared with the usage of LIAFS or DRS only. We also applied colorimetric transformation of the reflectance spectra detected and received additional evaluation criteria for determination of type of the lesion under study. Spectra from healthy skin areas near the lesion were detected and changes between healthy and lesion skin spectra were revealed. The influence of the main skin pigments on the detected spectra is discussed and evaluation of possibilities for differentiation between malignant and benign lesions is performed based on their spectral properties. This research shows that the non-invasive and high-sensitive in vivo detection by means of appropriate light sources and detectors should be possible, related to the real-time determination of existing pathological conditions. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)

  11. Development of techniques for advanced optical contamination measurement with internal reflection spectroscopy, phase 1, volume 1

    NASA Technical Reports Server (NTRS)

    Hayes, J. D.

    1972-01-01

    The feasibility of monitoring volatile contaminants in a large space simulation chamber using techniques of internal reflection spectroscopy was demonstrated analytically and experimentally. The infrared spectral region was selected as the operational spectral range in order to provide unique identification of the contaminants along with sufficient sensitivity to detect trace contaminant concentrations. It was determined theoretically that a monolayer of the contaminants could be detected and identified using optimized experimental procedures. This ability was verified experimentally. Procedures were developed to correct the attenuated total reflectance spectra for thick sample distortion. However, by using two different element designs the need for such correction can be avoided.

  12. Application of backward diffuse reflection spectroscopy for monitoring the state of tissues in photodynamic therapy

    SciTech Connect

    Stratonnikov, Aleksandr A; Meerovich, G A; Ryabova, A V; Savel'eva, T A; Loshchenov, V B

    2006-12-31

    The application of backward diffuse reflection (BDR) spectroscopy for in vivo monitoring the degree of haemoglobin oxygenation and concentration of photosensitisers in tissues subjected to photodynamic therapy is demonstrated. A simple experimental technique is proposed for measuring diffuse reflection spectra. The measurements are made under steady-state conditions using a fibreoptic probe with one transmitting and one receiving fibre separated by a fixed distance. Although this approach does not ensure the separation of contributions of scattering and absorption to the spectra being measured, it can be used for estimating the degree of haemoglobin oxygenation and concentration of photosensitisers in the tissues. Simple expressions for estimating the concentration of photosensitisers from the BDR spectra are presented and the accuracy of this approach is analysed. The results of application of BDR spectroscopy for monitoring various photosensitisers are considered. (special issue devoted to multiple radiation scattering in random media)

  13. Modelling of sensory and instrumental texture parameters in processed cheese by near infrared reflectance spectroscopy.

    PubMed

    Blazquez, Carmen; Downey, Gerard; O'Callaghan, Donal; Howard, Vincent; Delahunty, Conor; Sheehan, Elizabeth; Everard, Colm; O'Donnell, Colm P

    2006-02-01

    This study investigated the application of near infrared (NIR) reflectance spectroscopy to the measurement of texture (sensory and instrumental) in experimental processed cheese samples. Spectra (750 to 2498 nm) of cheeses were recorded after 2 and 4 weeks storage at 4 degrees C. Trained assessors evaluated 9 sensory properties, a texture profile analyser (TPA) was used to record 5 instrumental parameters and cheese 'meltability' was measured by computer vision. Predictive models for sensory and instrumental texture parameters were developed using partial least squares regression on raw or pre-treated spectral data. Sensory attributes and instrumental texture measurements were modelled with sufficient accuracy to recommend the use of NIR reflectance spectroscopy for routine quality assessment of processed cheese. PMID:16433962

  14. A model for testing strong gravity via X-ray reflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Bambi, Cosimo; Nampalliwar, Sourabh; Cardenas-Avendano, Alejandro

    2016-07-01

    Astrophysical black hole candidates are thought to be the Kerr black holes of general relativity. However, a direct observational evidence is still lacking. The X-ray radiation produced in the inner part of the accretion disk can be a powerful tool to test the Kerr nature of these objects. In this talk, we present a new model for testing the Kerr black hole hypothesis via X-ray reflection spectroscopy. We employ the formalism of the transfer function proposed by Cunningham 40 years ago. The transfer function acts as an integration kernel and takes into account all the relativistic effects. We have developed a code to compute transfer functions in arbitrary stationary and axisymmetric spacetimes. These transfer functions are tabulated in FITS files and combined with XILLVER. The result is best model that we can have today for testing black hole candidates via X-ray reflection spectroscopy.

  15. Titanium-silicon oxide film structures for polarization-modulated infrared reflection absorption spectroscopy

    PubMed Central

    Dunlop, Iain E.; Zorn, Stefan; Richter, Gunther; Srot, Vesna; Kelsch, Marion; van Aken, Peter A.; Skoda, Maximilian; Gerlach, Alexander; Spatz, Joachim P.; Schreiber, Frank

    2010-01-01

    We present a titanium-silicon oxide film structure that permits polarization modulated infrared reflection absorption spectroscopy on silicon oxide surfaces. The structure consists of a ~6 nm sputtered silicon oxide film on a ~200 nm sputtered titanium film. Characterization using conventional and scanning transmission electron microscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy and X-ray reflectometry is presented. We demonstrate the use of this structure to investigate a selectively protein-resistant self-assembled monolayer (SAM) consisting of silane-anchored, biotin-terminated poly(ethylene glycol) (PEG). PEG-associated IR bands were observed. Measurements of protein-characteristic band intensities showed that this SAM adsorbed streptavidin whereas it repelled bovine serum albumin, as had been expected from its structure. PMID:20418963

  16. Dynamic disorder in horseradish peroxidase observed with total internal reflection fluorescence correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Hassler, Kai; Rigler, Per; Blom, Hans; Rigler, Rudolf; Widengren, Jerker; Lasser, Theo

    2007-04-01

    This paper discusses the application of objective-type total internal reflection fluorescence correlation spectroscopy (TIR-FCS) to the study of the kinetics of immobilized horseradish peroxidase on a single molecule level. Objective-type TIR-FCS combines the advantages of FCS with TIRF microscopy in a way that allows for simultaneous ultra-sensitive spectroscopic measurements using a single-point detector and convenient localization of single molecules on a surface by means of parallel imaging.

  17. TOTAL INTERNAL REFLECTION WITH FLUORESCENCE CORRELATION SPECTROSCOPY: APPLICATIONS TO SUBSTRATE-SUPPORTED PLANAR MEMBRANES

    PubMed Central

    Thompson, Nancy L.; Wang, Xiang; Navaratnarajah, Punya

    2009-01-01

    In this review paper, the conceptual basis and experimental design of total internal reflection with fluorescence correlation spectroscopy (TIR-FCS) is described. The few applications to date of TIR-FCS to supported membranes are discussed, in addition to a variety of applications not directly involving supported membranes. Methods related, but not technically equivalent, to TIR-FCS are also summarized. Future directions for TIR-FCS are outlined. PMID:19269331

  18. Terahertz spectroscopic investigation of four kinds of vitamins

    NASA Astrophysics Data System (ADS)

    Zhao, Guozhong; Yu, Bin; Zhang, Cunlin

    2009-11-01

    The terahertz spectra of four kinds of vitamins are presented. The refractive index and absorption spectra of these vitamins are obtained by the terahertz time-domain spectroscopy. The full-geometry optimizations and frequency calculations using the density functional theory are applied to obtain the structure and vibration frequencies of these vitamin molecules. The calculated vibration frequencies are compared with the experimental data. The results show that there are terahertz fingerprint absorptions for all of four kinds of vitamins. The terahertz absorbance spectra of vitamins result from not only the intramolecular vibration modes, but also the intermolecular interaction or phonon modes.

  19. Multiple spatially resolved reflection spectroscopy for in vivo determination of carotenoids in human skin and blood

    NASA Astrophysics Data System (ADS)

    Darvin, Maxim E.; Magnussen, Björn; Lademann, Juergen; Köcher, Wolfgang

    2016-09-01

    Non-invasive measurement of carotenoid antioxidants in human skin is one of the important tasks to investigate the skin physiology in vivo. Resonance Raman spectroscopy and reflection spectroscopy are the most frequently used non-invasive techniques in dermatology and skin physiology. In the present study, an improved method based on multiple spatially resolved reflection spectroscopy (MSRRS) was introduced. The results obtained were compared with those obtained using the ‘gold standard’ resonance Raman spectroscopy method and showed strong correlations for the total carotenoid concentration (R  =  0.83) as well as for lycopene (R  =  0.80). The measurement stability was confirmed to be better than 10% within the total temperature range from 5 °C to  +  30 °C and pressure contact between the skin and the MSRRS sensor from 800 Pa to 18 000 Pa. In addition, blood samples taken from the subjects were analyzed for carotenoid concentrations. The MSRRS sensor was calibrated on the blood carotenoid concentrations resulting in being able to predict with a correlation of R  =  0.79. On the basis of blood carotenoids it could be demonstrated that the MSRRS cutaneous measurements are not influenced by Fitzpatrick skin types I-VI. The MSRRS sensor is commercially available under the brand name biozoom.

  20. Multiple spatially resolved reflection spectroscopy for in vivo determination of carotenoids in human skin and blood

    NASA Astrophysics Data System (ADS)

    Darvin, Maxim E.; Magnussen, Björn; Lademann, Juergen; Köcher, Wolfgang

    2016-09-01

    Non-invasive measurement of carotenoid antioxidants in human skin is one of the important tasks to investigate the skin physiology in vivo. Resonance Raman spectroscopy and reflection spectroscopy are the most frequently used non-invasive techniques in dermatology and skin physiology. In the present study, an improved method based on multiple spatially resolved reflection spectroscopy (MSRRS) was introduced. The results obtained were compared with those obtained using the ‘gold standard’ resonance Raman spectroscopy method and showed strong correlations for the total carotenoid concentration (R  =  0.83) as well as for lycopene (R  =  0.80). The measurement stability was confirmed to be better than 10% within the total temperature range from 5 °C to  +  30 °C and pressure contact between the skin and the MSRRS sensor from 800 Pa to 18 000 Pa. In addition, blood samples taken from the subjects were analyzed for carotenoid concentrations. The MSRRS sensor was calibrated on the blood carotenoid concentrations resulting in being able to predict with a correlation of R  =  0.79. On the basis of blood carotenoids it could be demonstrated that the MSRRS cutaneous measurements are not influenced by Fitzpatrick skin types I–VI. The MSRRS sensor is commercially available under the brand name biozoom.