Optical constants of CuO and ZnO particles in the terahertz frequency range

 Calvo-de la Rosa, Jaume, Alexandre Locquet, Denis Bouscaud, Sophie Berveiller, and D. S. Citrin. "Optical constants of CuO and ZnO particles in the terahertz frequency range." Ceramics International (2020).

Abstract

The optical constants (complex dielectric function) of CuO and ZnO particles in polyethylene pellets are measured by terahertz time-domain spectroscopy. The determination of the dielectric properties of these materials is of interest for energy-storage applications, for instance. Maxwell-Garnett theory is used to extract the contribution to the frequency-dependent optical constants of the oxide powders. The validity of the assumptions of Maxwell-Garnett theory are experimentally verified and self-consistency of the results of the model confirmed. On this basis, experimental complex permittivity values for isotropic CuO and ZnO oxide powders are reported in the 100 GHz-3 THz range.

for full paper see https://www.sciencedirect.com/science/article/pii/S0272884220318502

"THz transmission data through the pellets were obtained using a TeraView TPS Spectra 3000 in transmission mode. The experimental bandwidth (power spectrum of "

Microelectromechanically tunable multiband metamaterial with preserved isotropy

Abstract

We experimentally demonstrate a micromachined reconfigurable metamaterial with polarization independent characteristics for multiple resonances in terahertz spectral region. The metamaterial unit cell consists of eight out-of-plane deformable microcantilevers placed at each corner of an octagon ring. The octagon shaped unit cell geometry provides the desired rotational symmetry, while the out-of-plane movable cantilevers preserves the symmetry at different configurations of the metamaterial. The metamaterial is shown to provide polarization independent response for both electrical inductive-capacitive (eLC) resonance and dipolar resonance at all states of actuation. The proposed metamaterial has a switching range of 0.16 THz and 0.37 THz and a transmission intensity change of more than 0.2 and 0.7 for the eLC and dipolar resonances, respectively for both TE and TM modes. Further optimization of the metal layer thickness, provides an improvement of up to 80% modulation at 0.57 THz. The simultaneously tunable dual band isotropic metamaterial will enable the realization of high performance electro-optic devices that would facilitate numerous terahertz applications such as compressive terahertz imaging, miniaturized terahertz spectroscopy and next generation high speed wireless communication possible in the near future.

All THz transmission spectra measured in this paper were acquired using TeraView's TPS Spectra 3000.

http://www.nature.com/srep/2015/150626/srep11678/full/srep11678.html

Properties of two-component nematic liquid crystal mixtures in the range of 0.3–3.0 THz

TeraView's TPS Spectra 3000 was used to investigate nematic liquid crystals in the range of 0.3–3.0 THz.


http://www.tandfonline.com/doi/abs/10.1080/02678292.2015.1036816#.VYvdFvlViko


Abstract

In this work, we present the results of terahertz measurements of five nematic liquid crystal materials. Optical properties like refractive indices, birefringence and absorption coefficients of liquid crystals (LCs) for ordinary and extraordinary polarisation were compared. The aim of this study was to check the impact of the structure of LC molecules on above properties. The compounds with different core structure and various number of laterally substituted fluorine atoms were chosen. A standard terahertz Time-Domain Spectrometer to measurements from 0.3 THz to 3 THz was used.

Investigation of thermal degradation of vegetable oils by spectroscopic methods and its mathematical analysis

M. Tobolova, V. Kresalek, H. Vaskova and M. Buckova

Abstract

In this paper, relatively new spectroscopic methods were used for investigation of edible oils and their thermal degradation. There were included the samples of refined rapeseed and sunflower oil and the same oils heated for specified time interval at the temperature 200 °C. The optical characteristics of oils have been investigated with Terahertz Time Domain Spectroscopy (THz-TDS). The refractive indices were calculated in the specified terahertz frequency range, processed and statistically evaluated. The Wilcoxon matched pairs test was carried out for comparison of unheated and heated oil samples. The results measured by THz-TDS were supplemented by Raman spectra analysis. Both methods seem to be capable analyzing tool for oil investigation. 

This study was performed using TeraView's Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://www.naun.org/main/NAUN/mcs/2014/a122002-078.pdf

Detection of Melamine in Foods Using Terahertz Time-Domain Spectroscopy

Seung Hyun Baek, Heung Bin Lim, and Hyang Sook Chun

Abstract

The aim of this study was to investigate the feasibility of detecting melamine in foodstuffs using terahertz imaging. The terahertz (THz) spectra and images of melamine mixtures were obtained in the frequency range of 0.1–3 THz at room temperature using THz time-domain spectroscopy. Characteristic absorption peaks of melamine were found at 2, 2.26, and 2.6 THz, and these peaks showed the same frequencies in the different food matrices. At 2 THz, the THz images of melamine were dose-dependently distinguishable from those of food components with or without the packaging materials used. The calibration curve of melamine showed a regression coefficient (R2) of >0.913 and a detection limit of <13%. These results suggest that terahertz imaging has the potential to be used for the qualitative detection of melamine in food as a nondestructive analytical tool.

This study was performed using TeraView's TPS spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://pubs.acs.org/doi/abs/10.1021/jf501170z

Structural and chemical modification of nontronite associated with microbial Fe(III) reduction: Indicators of “illitization”

Tae-hee Kooa, Young-nam Jangb, Toshihiro Kogurec, Jae Hoon Kimd, Byung Cheol Parkd, Don Sunwooe, Jin-wook Kima,

Abstract

The smectite-to-illite reaction, termed illitization, is a ubiquitous process in siliciclastic sedimentary environments and plays a significant role in biogeochemical cycling, plant nutrition, petroleum maturation/migration, particle dispersion–aggregation, and contaminant uptake. The change in the redox state of structural Fe in smectite as a consequence of microbial Fe respiration, in part, controls the physicochemical properties of smectite, but knowledge of the chemical/structural modification at a nanoscale, particularly the reversibility of the structure and K fixation at various Fe-redox states that could control illitization, is limited. The present study focused on measuring indicators of illitization at a nanoscale, utilizing transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS) and terahertz time-domain spectroscopy (THz-TDS), as well as chemical analysis, including cation exchange capacity (CEC) and Fe(III) reduction. Nontronite (NAu-1) of the size fraction less than 0.2 m was inoculated with the Fe-reducing bacteria Shewanella oneidensis MR-1 in M1 medium with structural Fe(III) in NAu-1 as the sole electron acceptor and Na-lactate as the electron donor. Incubation continued for up to 12 months in an anaerobic chamber. Two sets of microbial structural Fe(III) reduction experiments were performed, and then one set was re-oxidized by bubbling pure oxygen gas through an autoclaved needle for 24 hours. The reaction was stopped at various time points by freezing the samples with liquid N₂. The extent of Fe(III) reduction reached 26%; 5% of residual Fe(II) was detected upon re-oxidation. TEM and X-ray diffraction (XRD) analyses confirmed the presence of an illite-like packet with collapsed 10-Å basal spacing in the Fe-reduced nontronite sample and permanently fixed K after long-term incubation. The proportion of K fixation in the interlayer increased with the extent of Fe(III) reduction and the amount of residual Fe(II) upon re-oxidation. The values of CEC increased corresponding to the extent of Fe(III) reduction; the CEC was not restored after re-oxidation, most likely due to the increase in residual Fe(II), secondary phase mineral (vivianite) precipitation, and permanent K fixation. Nondestructive THz-TDS depicted the chemical/structural modification of bioreduced nontronite and its reversibility. In the present study, true illite was not formed because of the low value of Al/Si; however, the progressive increase in K/(K + 2Ca) and Al/Si in the packets of 10-Å layers as well as the chemical/structural irreversibility upon re-oxidation with increasing incubation time strongly suggested illitization.

This study was performed using TeraView's TPS spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://www.sciencedirect.com/science/article/pii/S0009254114001880

Frequency Dependent Optical and Dielectric Properties of Zinc Sulfide in Terahertz Regime

Abstract

Frequency dependent optical and dielectric properties for several grades of chemical vapor deposited (CVD) zinc sulfide (standard, elemental, and multi-spectral) was performed using a terahertz time-domain spectroscopy (THz-TDS) system in the frequency range from 0.15 THz to 2.5 THz. Zinc sulfide exhibits low frequency vibrational modes characterized by the THz-TDS. Two low-frequency phonon resonance lines were revealed at 0.78, and 2.20 THz. These samples were also characterized in the GHz range using a backward wave oscillator (BWO) source quasi-optical spectrometer, and the data obtained by both approaches were compared. Experimental data were also compared with an undamped harmonic oscillator model. These results compare well with the literature values obtained using other methods.

This study was performed using TeraView's TPS spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://www.sciencedirect.com/science/article/pii/S1350449514000541

Influence of terahertz waves on the penetration in thick FRP composite materials

Kwang-Hee Im¹, David K. Hsu², Chien-Ping Chiou², Daniel J. Barnard², In-Young Yang³ and Je-Woong Park⁴


Abstract

Fiber reinforced plastics (FRP) are increasingly utilized in engineering structures because of their performance and fabrication advantages. With this increased utilization, a technique to gage quality and further characterize the materials would be beneficial. The nondestructive applications for Terahertz (T-ray) methods have also experienced increased utilization for evaluating engineering materials and will be reported on here in applications for the inspectionand characterization of FRP materials used in wind energy components. First, refraction and transmission T-ray modes are used to determine the refractive index (n) of a glass fiber reinforced plastic (GFRP) reference sample, and extended for calculating the refractive indicesfor a sample of GFRP, balsa and epoxy. Additionally, carbon fiber reinforced plastic (CFRP) samples were evaluated with respect to fiber directions versus T-ray electric field polarization direction to evaluate the level of penetration of T-ray energy due to the fiber orientation dependent conductivity of this composite material. Finally, an evaluation of T-ray data was made to evaluate resonance effects, where the resonance frequency was found to agree with that expected from reflections from individual plies in thick GFRP laminates.

This study was performed using TeraView's CW Spectra 400 system. (TeraView, Cambridge, UK)

Full Article: http://scitation.aip.org/content/aip/proceeding/aipcp/10.1063/1.4865010

Terahertz dual-band pass filter using double-layer reformative complementary metamaterial structures

Feng Lan, Ziqiang Yang, Limei Qi, Xi Gao, and Zongjun Shi


Abstract

A dual-band frequency selective surface filter in the THz range that uses double-layer modified complementary metamaterial structures is proposed in this paper. The band-pass filter, with dual bands centered at 0.315 THz and 0.48 THz, uses a single crystal quartz substrate and is simulated, fabricated and measured. To minimize the manufacturing risks of working with fragile and thin quartz substrates, efforts have been made to improve the transmission frequency response features at realizable substrate thicknesses. Experimental results from 0.1 THz to 0.6 THz measured by THz time-domain spectroscopy show excellent agreement with the simulation results.


Full Article: http://www.opticsinfobase.org/ol/upcoming_pdf.cfm?id=202012

Low-Bias THz Amplitude Modulator Based on Split-Ring Resonators and Graphene

Riccardo Degl'Innocenti , Davide Stephan Jessop , Yash Diptesh Shah , Juraj Sibik , J Axel Zeitler , Piran Ravichandran Kidambi , Stephan Hofmann , Harvey E Beere , and David Ritchie


Abstract

Split-ring resonators represent the ideal route to achieve optical control of the incident light at THz frequencies. These sub-wavelength metamaterial elements exhibit broad resonances that can be easily tuned lithographically. We realized a design based on the interplay between the resonances of metallic split-rings and the electronic properties of a monolayer graphene integrated in a single device. By varying the major carrier concentration of graphene, an active modulation of the optical intensity was achieved in the frequency range between 2.2 THz and 3.1 THz, achieving a maximum modulation depth of 18\%, with a bias as low as 0.5 V.

This study was performed using TeraView's TPI Imaga 2000 system. (TeraView, Cambridge, UK)

Full Article: http://pubs.acs.org/doi/abs/10.1021/nn406136c

Terahertz Imaging for Nondestructive Evaluation of Packaged Power Electronic Devices

Nathan M. Burford1, Magda O. El-Shenawee2, Chad B. O’Neal3, Kraig J. Olejniczak4


Abstract

Terahertz (THz) time-domain imaging of power electronic devices is performed using the commercial TPSTM Spectra 3000 THz imaging and spectroscopy system. The dimensions of bond wires within power transistor packages are extracted and the time-of-flight tomography is used to illustrate depth profiling of features in the device package. The devices under test in this paper are plastic encapsulated. The encapsulation measures a few millimeters thick. The THz images obtained in the reflection mode demonstrate a potential tool for the non-destructive inspection of packaged power electronic devices.

This study was performed using TeraView's TPS Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://www.ijetae.com/files/Volume4Issue1/IJETAE_0114_69.pdf

Determination of carrier concentration dependent electron effective mass and scattering time of n-ZnO thin film by terahertz time domain spectroscopy

J. Tang1,2, L. Y. Deng1, C. B. Tay1,2, X. H. Zhang3, J. W. Chai3, H. Qin4, H. W. Liu5, T. Venkatesan2 and S. J. Chua1,2,3,a)

Abstract

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 combiningterahertz 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 0.23m0 to 0.26m0 as the electron concentration changes from 5.9 × 10¹⁷ cm⁻³ to 4.0 × 10¹⁹ cm⁻³. The carrier concentrationdependent 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.

This study was performed using TeraView's TPS Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://scitation.aip.org/content/aip/journal/jap/115/3/10.1063/1.4861421

Terahertz electrodynamics and superconducting energy gap of NbTiN

Taeyoon Hong¹, Kyujin Choi¹, Kyung Ik Sim¹, Taewoo Ha¹, Byung Cheol Park¹,Hirotake Yamamori² and Jae Hoon Kim^1,a)

Abstract

Terahertz electrodynamics of superconducting NbTiN has been studied in the spectral range of 8-70 cm^–1 above and below the critical temperature of Tc  = 14.1 K. Our transmission terahertz time-domain spectroscopy technique allows for independent and accurate determination of both the real part σ1 and the imaginary part σ2 of the optical conductivity σ as a function of frequency ω and temperature T without a Kramers-Kronig analysis. A clear signature of the superconducting energy gap Δ(T) is observed in the real part σ1 of the optical conductivity belowTc , with 2Δ(0) = 36.5 cm⁻¹ corresponding to 2Δ(0)/kBTc  = 3.72. No indication of strong-coupling effects was observed in the imaginary part σ2 toward zero frequency. Our results, including the temperature dependence of the penetration depth λ(T), are in excellent quantitative agreement with weak coupling BCS theory and Mattis-Bardeen formula.

This study was performed using TeraView's TPS Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://scitation.aip.org/content/aip/journal/jap/114/24/10.1063/1.4856995

Identification of concealed materials, including explosives, by terahertz reflection spectroscopy

Norbert Palka

Military University of Technology

Abstract

We report on a method for extracting the characteristic features of covered materials, including hexogen, in the range from 0.5 to 1.8 THz. This time-domain spectroscopy-based technique takes into account only part of the signal reflected from a covered sample and analyzes it by using the Fourier transform. The obtained power spectrum has distinctive peaks that correspond to peaks measured in the transmission configuration and can be used for further identification of the materials.

This study was performed using TeraView's TPS Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://opticalengineering.spiedigitallibrary.org/article.aspx?articleid=1787555

Influence of high-pressure treatment on charge carrier transport in PbS colloidal quantum dot solids

Seung Jin Heo,   Seokhyun Yoon,   Sang Hoon Oh,   Doo Hyun Yoon and    Hyun Jae Kim -Nanoscale, 2013

Abstract 

We investigated the effects of high-pressure treatment on charge carrier transport in PbS colloidal quantum dot (CQD) solids. We applied high pressure to PbS CQD solids using nitrogen gas to reduce the inter-dot distance. Using this simple process, we obtained conductive PbS CQD solids. Terahertz time-domain spectroscopy was used to study charge carrier transport as a function of pressure. We found that the minimum pressure needed to increase the dielectric constant, conductivity, and carrier mobility was 4 MPa. All properties dramatically improved at 5 MPa; for example, mobility increased from 0.13 cm2 V-1 s-1 at 0.1 MPa to 0.91 cm2 V-1 s-1 at 5 MPa. We propose this simple process as a nondestructive approach for making conductive PbS CQD solids that are free of chemical and physical defects.

This study was performed using TeraView's TPS Spectra 3000 system (TeraView, Cambridge, UK) 
Original Article: http://pubs.rsc.org/en/content/articlelanding/2013/nr/c3nr03641c#!divAbstract

Phonon Energy Gaps in the Charged Incommensurate Planes of the Spin-Ladder Sr14Cu24O41 Compound by Raman and Infrared Spectroscopy (FULL TEXT)

Physical Review Letters 108, 217401 (2012)
© 2012 American Physical Society
url: http://link.aps.org/doi/10.1103/PhysRevLett.108.217401
doi: 10.1103/PhysRevLett.108.217401
PACS:  78.30.-j, 71.45.Lr, 78.70.Gq

Authors: V. K. Thorsmølle1,2,4,*, C. C. Homes3,†, A. Gozar3,‡, G. Blumberg4, J. L. M. van Mechelen2, A. B. Kuzmenko2, S. Vanishri5, C. Marin5, and H. M. Rønnow6
1 Laboratory for Photonics and Interfaces, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Switzerland2 Département de Physique de la Matière Condensée, Université de Genève, CH-1211 Genève 4, Switzerland3 Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA4 Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, USA5 CEA Grenoble, INAC, SPSMS, IMAPEC, 17 rue des Martyrs, 38054 Grenoble, France6Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015, Switzerland

Abstract

The terahertz (THz) excitations in the quantum spin-ladder system Sr14Cu24O41 have been determined along the c axis using THz time-domain, Raman, and infrared spectroscopy. Low-frequency infrared and Raman active modes are observed above and below the charge-ordering temperature Tco≃200  K over a narrow interval ≃1–2  meV (≃8–16  cm-1). A new infrared mode at ≃1  meV develops below ≃100  K. The temperature dependence of these modes shows that they are coupled to the charge- and spin-density-wave correlations in this system. These low-energy features are conjectured to originate in the gapped sliding motion of the chain and ladder subsystems, which are both incommensurate and charged.

...The THz-TDS experiments (TPI spectra 1000, TeraView Ltd.) were performed in transmission geometry with the sample mounted inside an optical cryostat capable of reaching 5 K...

Full text available at:
http://girsh.rutgers.edu/Papers/Verner_PhysRevLett.108.217401.pdf

Terahertz Time Domain Spectroscopy of Human Blood

Biomedical and Health Informatics, IEEE Journal of
Issue: 99
Authors: Reid, C; Reese, G.; Gibson, A.P.; Wallace, V.P.
Department of Medical Physics and Bioengineering, University College London

Abstract

In the continuing development of terahertz technology to enable the determination of tissue pathologies in real-time during surgical procedures, it is important to distinguish the measured terahertz signal from biomaterials and fluids, such as blood, which may mask the signal from tissues of interest. In this paper, we present the frequency-dependent absorption coefficients, refractive indices and Debye relaxation times of whole blood, red blood cells, plasma and a thrombus.

... Methods Experimental method A stand-alone portable THz system, the TPI Imaga1000 (TeraView Ltd, Cambridge, UK), was used in this work. A full description of the system operation is given elsewhere [19], however it is briefly described here for clarity...

More info at: http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6506093&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6506093

Investigation on the Terahertz Absorption Spectra of the Molecules with Similar Molecular Structure

Conference Paper from Laser and Tera-Hertz Science and Technology

Wuhan, China, November 1, 2012
THz Spectroscopy and Imaging (SF3A)
Author: Wenhui Fan; http://dx.doi.org/10.1364/LTST.2012.SF3A.1
+The Optical Society (OSA)

Abstract

The characteristic terahertz absorption features of several molecules with similar molecular structure have been measured by terahertz time-domain spectroscopy experimentally. Theoretical simulations have also been performed, and all measured terahertz absorption features are assigned.

More info at: http://www.opticsinfobase.org/abstract.cfm?URI=LTST-2012-SF3A.1

Terahertz Spectroscopy and Imaging - New Book

Series: Springer Series in Optical Sciences, Vol. 171,2013, XXXI, 641 p.

Authors: Peiponen, Kai-Erik; Zeitler, Axel; Kuwata-Gonokami, Makoto (Eds.

+SpringerMaterials
More details at: http://www.springer.com/physics/optics+%26+lasers/book/978-3-642-29563-8

• Presents the state-of-the-art of Terahertz spectroscopy
• Gives a concise presentation of the basics of THz spectroscopy
• Describes important applications of THz technology

"This book presents the current state of knowledge in the field of terahertz spectroscopy, providing a comprehensive source of information for beginners and experienced researchers alike whose interests lie in this area. The book aims to explain the fundamental physics that underpins terahertz technology and to describe its key applications. Highlights of scientific research in the field of terahertz science are also outlined in some chapters, providing an overview as well as giving an insight into future directions for research.

Over the past decade terahertz spectroscopy has developed into one of the most rapidly growing areas of its kind, gaining an important impact across a wide range of scientific disciplines. Due to substantial advances in femtosecond laser technology, terahertz time-domain spectroscopy (THz-TDS) has established itself as the dominant spectroscopic technique for experimental scientists interested in measurements at this frequency range. In solids and liquids THz radiation is in resonance with both phonon modes and hydrogen bonding modes, which makes it an ideal tool to study the interaction between molecules in a unique way; thus opening a wealth of opportunities for research in physics, chemistry, biology, materials science and pharmaceuticals.

This book provides easy access to scientists, engineers and students who want to understand the theory and applications of modern THz spectroscopy."

Chapter: Industrial Applications of Terahertz Imaging

This chapter gives a concise overview of potential industrial applications for terahertz imaging that have been reported over the past decade with a discussion of the major advantages and limitations of each approach. In the second half of the chapter we discuss in more detail how terahertz imaging can be used to investigate the microstructure of pharmaceutical dosage forms. A particular focus in this context is the nondestructive measurement of the coating thickness of polymer coated tablets, both by means of high resolution offline imaging in research and development as well as for in-line quality control during production.


... Defect in copper trace (a) (b) Fig. 18.3 Electro Optical Terahertz Pulse Reflectometry (EOTPR) for semiconductor fault testing. a Optical images of the two failed devices showing the cut in the copper traces. b Results obtained with EOTPR (source: TeraView Ltd.) ...

More on applications of terahertz technology http://www.teraview.com/applications/index.html