Antenna-Coupled Titanium Microbolometers: Application for Precise Control of Radiation Patterns in Terahertz Time-Domain Systems

An ability of lensless titanium-based antenna coupled microbolometers (Ti-μbolometers) operating at room temperature to monitor precisely radiation patterns in terahertz time-domain spectroscopy (THz-TDS) systems are demonstrated. To provide comprehensive picture, two different THz-TDS systems and Ti-μbolometers coupled with three different antennas—narrowband dipole antennas for 0.3 THz, 0.7 THz and a log-periodic antenna for wideband detection—were selected for experiments. Radiation patterns, spatial beam profiles and explicit beam evolution along the propagation axis are investigated; polarization-sensitive properties under various THz emitter power ranges are revealed. It was found that the studied Ti-μbolometers are convenient lensless sensors suitable to discriminate and control THz radiation pattern features in various wideband THz-TDS systems.

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Terahertz Time-Domain Spectroscopy of Graphene Nanoflakes Embedded in Polymer Matrix

Applied Sciences ◽

10.3390/app9030391 ◽

2019 ◽

Vol 9 (3) ◽

pp. 391 ◽

Cited By ~ 1

Author(s):

Anton Koroliov ◽

Genyu Chen ◽

Kenneth M. Goodfellow ◽

A. Nick Vamivakas ◽

Zygmunt Staniszewski ◽

...

Keyword(s):

Polymer Matrix ◽

Time Domain ◽

Thz Radiation ◽

Complex Conductivity ◽

Frequency Range ◽

Terahertz Time Domain Spectroscopy ◽

Time Domain Spectroscopy ◽

Graphene Nanocomposites ◽

Graphene Nanoflakes ◽

Exfoliated Graphene

The terahertz time-domain spectroscopy (THz-TDS) technique has been used to obtain transmission THz-radiation spectra of polymer nanocomposites containing a controlled amount of exfoliated graphene. Graphene nanocomposites (1 wt%) that were used in this work were based on poly(ethylene terephthalate-ethylene dilinoleate) (PET-DLA) matrix and were prepared via a kilo-scale (suitable for research and development, and prototyping) in-situ polymerization. This was followed by compression molding into 0.3-mm-thick and 0.9-mm-thick foils. Transmission electron microscopy (TEM) and Raman studies were used to confirm that the graphene nanoflakes dispersed in a polymer matrix consisted of a few-layer graphene. The THz-radiation transients were generated and detected using a low-temperature–grown GaAs photoconductive emitter and detector, both excited by 100-fs-wide, 800-nm-wavelength optical pulses, generated at a 76-MHz repetition rate by a Ti:Sapphire laser. Time-domain signals transmitted through the nitrogen, neat polymer reference, and 1-wt% graphene-polymer nanocomposite samples were recorded and subsequently converted into the spectral domain by means of a fast Fourier transformation. The spectral range of our spectrometer was up to 4 THz, and measurements were taken at room temperature in a dry nitrogen environment. We collected a family of spectra and, based on Fresnel equations, performed a numerical analysis, that allowed us to extract the THz-frequency-range refractive index and absorption coefficient and their dependences on the sample composition and graphene content. Using the Clausius-Mossotti relation, we also managed to estimate the graphene effective dielectric constant to be equal to ~7 ± 2. Finally, we extracted from our experimental data complex conductivity spectra of graphene nanocomposites and successfully fitted them to the Drude-Smith model, demonstrating that our graphene nanoflakes were isolated in their polymer matrix and exhibited highly localized electron backscattering with a femtosecond relaxation time. Our results shed new light on how the incorporation of exfoliated graphene nanoflakes modifies polymer electrical properties in the THz-frequency range. Importantly, they demonstrate that the complex conductivity analysis is a very efficient, macroscopic and non-destructive (contrary to TEM) tool for the characterization of the dispersion of a graphene nanofiller within a copolyester matrix.

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Terahertz Time-Domain Spectroscopy Based on Commercially Available 1550 nm Fabry–Perot Laser Diode and ErAs:In(Al)GaAs Photoconductors

Applied Sciences ◽

10.3390/app9132704 ◽

2019 ◽

Vol 9 (13) ◽

pp. 2704 ◽

Cited By ~ 2

Author(s):

Kai-Henning Tybussek ◽

Kevin Kolpatzeck ◽

Fahd Faridi ◽

Sascha Preu ◽

Jan C. Balzer

Keyword(s):

Laser Diode ◽

Time Domain ◽

Dynamic Range ◽

Laser System ◽

Industrial Applications ◽

Thz Radiation ◽

Full Potential ◽

Terahertz Time Domain Spectroscopy ◽

Time Domain Spectroscopy ◽

Fabry Perot

THz time-domain spectroscopy (TDS) is a promising tool for quality control purposes in industrial applications, but the high cost and the relatively large laser sources still make it difficult to use the full potential of the technology for a decent price. In this work, a THz TDS system, which uses a commercially available Fabry–Perot laser diode emitting at 1550 nm, is presented. By dispersion compensation, pulses with a duration of 544 fs were generated, resulting in THz radiation with a bandwidth of 1.4 THz and a peak dynamic range of 56 dB with state-of-the-art ErAs:In(Al)GaAs photoconducting antennas. These results are compared with those of a conventional and expensive fiber laser system with a 90 fs pulse duration.

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Application of Terahertz Spectroscopy and Imaging

Siberian Journal of Physics ◽

10.54362/1818-7919-2010-5-4-123-129 ◽

2010 ◽

Vol 5 (4) ◽

pp. 123-129

Author(s):

Mu Kaijun ◽

Zhang Cunlin

Keyword(s):

Time Domain ◽

Quartz Crystal ◽

Terahertz Spectroscopy ◽

Thz Radiation ◽

Radiation Polarization ◽

Air Plasma ◽

Thz Imaging ◽

Terahertz Time Domain Spectroscopy ◽

Security Applications ◽

Angle Of Rotation

We examined the feasibility of Terahertz time-domain spectroscopy (THz-TDS) using a 4-mm-thick quartz crystal to extract the angle of rotation of THz radiation polarization induced by a two-color laser in air plasma. We also used the THz-TDS technique to identify explosives and melamine in mixtures. In addition, we presented a new opto-mechanical scanner for security applications using the method of passive THz imaging

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Terahertz Time-domain Spectroscopy as a Novel Tool for Crystallographic Analysis in Cellulose: Cellulose I to Cellulose Ii, Tracing the Structural Changes Under Chemical Treatment

10.21203/rs.3.rs-864353/v1 ◽

2021 ◽

Author(s):

Han Wang ◽

Hiroki Kataoka ◽

Satoru Tsuchikawa ◽

Tetsuya Inagaki

Keyword(s):

Absorption Coefficient ◽

Time Domain ◽

Structural Changes ◽

Crystalline Lattice ◽

Thz Radiation ◽

Cellulose Ii ◽

Cellulose I ◽

Terahertz Time Domain Spectroscopy ◽

Time Domain Spectroscopy ◽

Thz Absorption

Abstract Terahertz time-domain spectroscopy (THz-TDS) has expanded possibilities in cellulose crystallography research, as THz radiation detects most intermolecular vibrations and responds to the phonons of crystalline lattices. In this study, we traced the transformation of the cellulose crystalline lattice from cellulose I to cellulose II by THz-TDS and X-ray powder diffraction. Cellulose II was obtained by treating cellulose I with NaOH of different concentrations (0 wt%–20 wt%, at 2 wt% intervals). The THz absorption coefficient spectra of cellulose II showed three characteristic peaks (at 1.32 THz, 1.76 THz, and 2.77 THz). The THz absorption coefficient spectra of cellulose II treated with 20-wt% NaOH and cellulose I without NaOH treatment were fitted by a seventh-order Fourier series. Thus, the THz absorption coefficient spectra of samples treated with NaOH of other concentrations could be considered a combination of these two fitted profiles of cellulose I and cellulose II, multiplied by different coefficients. Furthermore, the coefficients could reflect the relative contents of cellulose I and cellulose II in the samples.

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Thz radiation patterns from semiconductor dipole antennas

Proceedings of 5th European Quantum Electronics Conference ◽

10.1109/eqec.1994.698393 ◽

2005 ◽

Author(s):

P.U. Jepsen ◽

S.R. Keiding

Keyword(s):

Thz Radiation ◽

Radiation Patterns ◽

Dipole Antennas

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Investigation of Dielectric Properties of Polymers and their Discrimination Using Terahertz Time-Domain Spectroscopy with Principal Component Analysis

Applied Spectroscopy ◽

10.1177/0003702816675361 ◽

2016 ◽

Vol 71 (3) ◽

pp. 456-462 ◽

Cited By ~ 16

Author(s):

Muhammad Mumtaz ◽

Ahsan Mahmood ◽

Sabih D. Khan ◽

M. Aslam Zia ◽

Mushtaq Ahmed ◽

...

Keyword(s):

Spectral Range ◽

Time Domain ◽

Principal Component ◽

Component Analysis ◽

Thz Radiation ◽

Terahertz Time Domain Spectroscopy ◽

Time Domain Spectroscopy ◽

Styrene Acrylonitrile ◽

Characteristic Features ◽

First Time

Polymers are among the most commonly used materials in our everyday life. They are generally transparent to terahertz (THz) radiation, but are quite difficult to differentiate using optical techniques as few or no characteristic features exist in the spectral range of <2.0 THz for small and portable radiation systems. In this work, we report experimental measurement of refractive indices and absorption coefficients of styrene acrylonitrile (SAN) and Bakelite in the spectral range of 0.2–2.0 THz for the first time. Additionally, we demonstrate that by combining principle component analysis (PCA) with THz time-domain spectroscopy one can differentiate such polymers. In this analysis, the first three principle components PC1, PC2, and PC3 depict >94% variance with a distribution of 72.45%, 11.52%, and 9.38%, respectively.

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Terahertz Time-domain Spectroscopy as a Novel Tool for Crystallographic Analysis in Cellulose: the Potentiality of Being a New Standard for Evaluating Crystallinity

10.21203/rs.3.rs-291523/v1 ◽

2021 ◽

Author(s):

Han Wang ◽

Satoru Tsuchikawa ◽

Tetsuya Inagaki

Keyword(s):

Ball Milling ◽

Time Domain ◽

Crystallinity Index ◽

Intermolecular Forces ◽

Crystallographic Analysis ◽

Thz Radiation ◽

Terahertz Time Domain Spectroscopy ◽

Time Domain Spectroscopy ◽

Mass Fractions ◽

Integrated Intensity

Abstract Given that terahertz (THz) radiation responds to intermolecular forces such as hydrogen bonds, THz time-domain spectroscopy (THz-TDS) has expanded possibilities in cellulose research. In this study, THz-TDS was used to investigate the crystallinity of three types of cellulose-based materials. Microcrystalline cellulose (MCC) and wood were ball milled at different times, and pseudo-wood was a mixture of MCC and lignin of different mass fractions. All the samples showed peaks at 3.04 THz in the THz mass absorption coefficient spectra. Further, the spectra from 2.79 THz to 3.32 THz were cut out and detrended by subtraction from a baseline. The integrated intensity of the detrended spectra showed a correlation with the mass fraction of lignin of the pseudo-wood samples, and ball milling time of the MCC and wood samples. The correlation was similar with the crystallinity index calculated from X-ray powder diffraction. Moreover, the original wood sample without ball milling had an integrated intensity that was about 30% that of the original MCC sample, matching with the cellulose concentration of the wood (about 30% to 40%). We normalized the integrated intensity of 2.79 THz to 3.32 THz into 1 to 0 by a min-max algorithm and proposed a new “index” for evaluating crystallinity.

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Optical and Galvanomagnetic Properties of Bi1-xSbx Thin Films in the Terahertz Frequency Range

Applied Sciences ◽

10.3390/app10082724 ◽

2020 ◽

Vol 10 (8) ◽

pp. 2724 ◽

Cited By ~ 2

Author(s):

Anton D. Zaitsev ◽

Petr S. Demchenko ◽

Dmitry V. Zykov ◽

Ekaterina A. Korotina ◽

Elena S. Makarova ◽

...

Keyword(s):

Thin Films ◽

Film Thickness ◽

Time Domain ◽

Hall Coefficient ◽

Transport Coefficients ◽

Thz Radiation ◽

Frequency Range ◽

Terahertz Time Domain Spectroscopy ◽

Time Domain Spectroscopy ◽

Mobility Of Charge Carriers

We report results of galvanomagnetic and terahertz time-domain spectroscopy measurements on thin films of Bi 1 − x Sb x on polyimide and mica substrates with various antimony concentrations (x from 0 to 15 %) and film thickness (70, 150 nm). The resistivity, Hall coefficient and magnetoresistivity of the films were measured experimentally in the magnetic field of 0.65 T at room temperature. Mobility and concentration of electrons and holes in the film plane were calculated using the transport coefficients. The terahertz time-domain spectroscopy is used to measure the complex conductivity and permittivity of Bi 1 − x Sb x thin films on the dielectric substrates in the frequency range from 0.2 to 1 THz. The plasma frequency, relaxation time, DC conductivity and effective carrier mass were extracted from these data and evaluated as functions of the Sb concentration for different film thickness and substrate. We observed that the film magnetoresistivity decreases with increasing the Sb concentration and for most of the films the Hall coefficient is negative and depends on the external factors insignificantly. We show that the mobility of charge carriers weakly depends on Sb concentration, which confirms the assertion about the scattering of carriers on themselves and not on defects in the structure. It was revealed that film static and dynamic resistivity (conductivity) as well as dielectric permittivity depend on Sb content and the film thickness. The results may be used for development of various thermoelectric, electronic and optical devices, such as THz detectors or components which can control the properties of THz radiation.

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Terahertz Time-Domain Spectroscopy

10.32386/scivpro.000006 ◽

2020 ◽

Vol 1 (1) ◽

pp. 1-4

Author(s):

Chiara Ciccarelli ◽

Hannah Joyce ◽

Jason Robinson ◽

Farhan Nur Kholid ◽

Dominik Hamara ◽

...

Keyword(s):

Thin Film ◽

Time Domain ◽

Terahertz Spectroscopy ◽

Thz Radiation ◽

Terahertz Time Domain Spectroscopy ◽

Technical Aspects ◽

Time Domain Data ◽

Scientific Disciplines ◽

Picosecond Time Scale ◽

Time Domain Terahertz Spectroscopy

Time-Domain terahertz spectroscopy (THz TDS) has attracted attention from many scientific disciplines as it enables accessing the gap between electronic and optical techniques. One application is to probe spintronic dynamics in sub-picosecond time scale. Here, we discuss principles and technical aspects of a typical THz TDS setup. We also show an example of terahertz time-domain data obtained from a Co/Pt thin film calibrant, which is a well-studied spintronic structure emitting strong THz radiation. See video at https://youtu.be/X7vrvQcmy8c.

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Narrow-Line Waveguide Terahertz Time-Domain Spectroscopy of Aspirin and Aspirin Precursors

Applied Spectroscopy ◽

10.1366/000370208783759768 ◽

2008 ◽

Vol 62 (3) ◽

pp. 319-326 ◽

Cited By ~ 40

Author(s):

N. Laman ◽

S. Sree Harsha ◽

D. Grischkowsky

Keyword(s):

Salicylic Acid ◽

Time Domain ◽

Low Frequency ◽

Far Infrared ◽

Metal Plate ◽

Thz Radiation ◽

Vibrational Modes ◽

Terahertz Time Domain Spectroscopy ◽

Time Domain Spectroscopy ◽

Parallel Plate Waveguide

Low frequency vibrational modes of pharmaceutical molecules are dependent on the molecule as a whole and can be used for identification purposes. However, conventional Fourier transform far-infrared spectroscopy (FT-IR) and terahertz time-domain spectroscopy (THz-TDS) often result in broad, overlapping features that are difficult to distinguish. The technique of waveguide THz-TDS has been recently developed, resulting in sharper spectral features. Waveguide THz-TDS consists of forming an ordered polycrystalline film on a metal plate and incorporating that plate in a parallel-plate waveguide, where the film is probed by THz radiation. The planar order of the film on the metal surface strongly reduces the inhomogeneous broadening, while cooling the waveguide to 77 K reduces the homogeneous broadening. This combination results in sharper absorption lines associated with the vibrational modes of the molecule. Here, this technique has been demonstrated with aspirin and its precursors, benzoic acid and salicylic acid, as well as the salicylic acid isomers 3- and 4-hydroxybenzoic acid. Linewidths as narrow as 20 GHz have been observed, rivaling single crystal measurements.

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