Experimental and Theoretical Study of Strong Low-Terahertz Absorption of Thymine

Zhang, W-D., A. Bykhovski, J. A. Deibel, and E. R. Brown. "Experimental and Theoretical Study of Strong Low-Terahertz Absorption of Thymine." Journal of Infrared, Millimeter, and Terahertz Waves 38, no. 12 (2017): 1521-1529.

Abstract

The absorption coefficient of a nucleobase-thymine-in powder form was measured with terahertz spectroscopy in both frequency- and time-domain experiments. For frequencies below 3 THz, a strong signature was observed at 1.27 THz. Furthermore, molecular-dynamic simulations were conducted to reveal that the 1.27 THz absorption signature is related to a transverse optical phonon mode. The simulations also indicated that bound water molecules are vital to the vibrational mode.

... 3 Experimental Methods and Results: Time-Domain Spectroscopy. Next to verify the frequency-domain result, we measured thymine samples with a time-domain system (Teraview TPS Spectra 3000) operating from 0.1 to ∼4.0 THz, and having a dynamic range of ∼60 dB ...

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For full paper see https://link.springer.com/article/10.1007/s10762-017-0420-z

Terahertz non-destructive imaging of cracks and cracking in structures of cement-based materials

Fan, Shujie, Tongchun Li, Jun Zhou, Xiaoqing Liu, Xiaoming Liu, Huijun Qi, and Zhiyong Mu. "Terahertz non-destructive imaging of cracks and cracking in structures of cement-based materials." AIP Advances 7, no. 11 (2017): 115202.

ABSTRACT

Cracks and crack propagation in cement-based materials are key factors leading to failure of structures, affecting safety in construction engineering. This work investigated the application of terahertz (THz) non-destructive imaging to inspections on structures of cement-based materials, so as to explore the potential of THz imaging in crack detection. Two kinds of disk specimens made of plain cement mortar and UHMWPE fiber concrete were prepared respectively. A mechanical expansion load device was deployed to generate cracks and control the whole process of cracking. Experimental tests were carried out on cracked specimens by using a commercial THz time domain spectroscopy (THz-TDS) during loading. The results show that crack opening and propagation could be examined by THz clearly and the material factors influence the ability of crack resistance significantly. It was found that the THz imaging of crack initiation and propagation agrees with the practical phenomenon and supplies more information about damage of samples. It is demonstrated that the damage behavior of structures of cement-based materials can be successfully detected by THz imaging.

....The THz imaging is throughout the whole loading procedure in Section 3.2. All of the TPI experiments were conducted using the TeraView TPS 3000 THz spectrometer,27 the main machine of which is shown in FIG. 5. .....

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For full paper see http://aip.scitation.org/doi/full/10.1063/1.4996053

Nondestructive Imaging of Packaged Microelectronics using Pulsed Terahertz Technology

Tyler Bowman and Magda El-Shenawee (2017) Nondestructive Imaging of Packaged Microelectronics using Pulsed Terahertz Technology. International Symposium on Microelectronics: Fall 2017, Vol. 2017, No. 1, pp. 000709-000714. https://doi.org/10.4071/isom-2017-THP23_160 Abstract This work presents the use of terahertz reflection imaging for nondestructive evaluation of packaged microelectronics. Power MOSFETs and SRAM devices are placed in a pulsed terahertz imaging system in the reflection mode with an incident angle of 30°. From the received signal at each point on the sample under test, the internal structure of the device can be clearly seen. For transistors, terahertz nondestructive imaging has been successful in determining die size and location as well as the bond wire size, number, and connections. High-pass frequency filters are utilized to enhance the image quality for viewing the bond wires. In addition, the terahertz B-scans are used to determine additional information including the vertical position of the bond wires and the die inside the packaged device. For the SRAM, the terahertz nondestructive imaging shows similar effectiveness in defining the layout of the metal connections inside the package and the wire positions. Thus terahertz imaging is shown to have a strong potential for nondestructive evaluation of these devices. ... This work makes use of the TPS Spectra 3000 (Teraview, Ltd., UK) pulsed terahertz imaging and spectroscopy system at the University of Arkansas. The system diagram is shown in Fig. 1a. ... For more information about TeraView visit https://www.azom.com/suppliers.aspx?SupplierID=12145 for full paper see http://www.imapsource.org/doi/abs/10.4071/isom-2017-THP23_160?code=imap-site

Dielectric properties of semi-insulating Fe-doped InP in the terahertz spectral region

Alyabyeva, L. N., E. S. Zhukova, M. A. Belkin, and B. P. Gorshunov. "Dielectric properties of semi-insulating Fe-doped InP in the terahertz spectral region." Scientific Reports 7 (2017).

Abstact

We report the values and the spectral dependence of the real and imaginary parts of the dielectric permittivity of semi-insulating Fe-doped InP crystalline wafers in the 2–700 cm−1 (0.06–21 THz) spectral region at room temperature. The data shows a number of absorption bands that are assigned to one- and two-phonon and impurity-related absorption processes. Unlike the previous studies of undoped or low-doped InP material, our data unveil the dielectric properties of InP that are not screened by strong free-carrier absorption and will be useful for designing a wide variety of InP-based electronic and photonic devices operating in the terahertz spectral range.

......The measurements of the dielectric properties in the ν = 0.21–3.00 THz range (7–100 cm−1) were performed using a pulsed THz TeraView TPS-Spectra-3000 time-domain spectrometer....

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https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5544691/

Preparation, characterization, and spectroscopy study on CdSe quantum dots linked to multi-walled carbon nanotubes

Abouelsayed, A., Badawi Anis, Aly Okasha, Ali M. Ali, W. Elhotaby, and Ahmed SG Khalil. "Preparation, characterization, and spectroscopy study on CdSe quantum dots linked to multi-walled carbon nanotubes." Materials Chemistry and Physics 203 (2018): 1-8.

Abstract

We present spectroscopy study on cadmium selenide (CdSe) quantum dots (QDs) with different particle sizes linked to multi-walled carbon nanotubes (MWCNTs), so-called (CdSe-QDs/MWCNTs), in the ultraviolet and visible frequency range. Drude-Lorentz (DL) model has been used for fitting the absorption spectra for the samples under investigations. Quantitative information about the different excitonic bands and the particle sizes of CdSe-QDs were obtained from the fitting curves and their components. Furthermore, noncontact terahertz time-domain spectroscopy technique was used to compare the optical properties of the MWCNTs and CdSe-QDs/MWCNTs. Using DL model, the optical conductivities have been estimated from the optical parameters obtained from the data extracted from the differential complex terahertz analysis in the frequency range of 0.06–3 THz. The results illustrate that the optical conductivity of MWCNTs is smaller compared to the CdSe-QDs/MWCNTs due to the increased number of free electrons transferred from CdSe QDs and the availability of mobile carriers.

... The absorption bands are deconvoluted and fitted by Lorentzian model. The transmission measurements have been performed in the terahertz frequency range using (TPS spectra 3000 system (Teraview Ltd. England) model under Nitrogen gas N 2 purging. ...

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http://www.sciencedirect.com/science/article/pii/S025405841730754X

Ultrathin tunable terahertz absorber based on MEMS-driven metamaterial

Liu, Mingkai, Mohamad Susli, Dilusha Silva, Gino Putrino, Hemendra Kala, Shuting Fan, Michael Cole et al. "Ultrathin tunable terahertz absorber based on MEMS-driven metamaterial." Microsystems & Nanoengineering 3 (2017): 17033.

Abstact

The realization of high-performance tunable absorbers for terahertz frequencies is crucial for advancing applications such as single-pixel imaging and spectroscopy. Based on the strong position sensitivity of metamaterials’ electromagnetic response, we combine meta-atoms that support strongly localized modes with suspended flat membranes that can be driven electrostatically. This design maximizes the tunability range for small mechanical displacements of the membranes. We employ a micro-electromechanical system technology and successfully fabricate the devices. Our prototype devices are among the best-performing tunable THz absorbers demonstrated to date, with an ultrathin device thickness (~1/50 of the working wavelength), absorption varying between 60% and 80% in the initial state when the membranes remain suspended, and fast switching speed (~27 μs). The absorption is tuned by an applied voltage, with the most marked results achieved when the structure reaches the snap-down state. In this case, the resonance shifts by 4200% of the linewidth (14% of the initial resonance frequency), and the absolute absorption modulation measured at the initial resonance can reach 65%. The demonstrated approach can be further optimized and extended to benefit numerous applications in THz technology.

.....To quantify the absorption properties of the samples, we measured the reflection spectra with a commercial THz time-domain spectrometer (TeraPulse4000, Teraview Ltd, Cambridge, UK). The incident angle of the THz beam in the spectrometer is 30°, and the polarization is dominated by the TE component........

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https://search.proquest.com/openview/6132b105e4dc0c6b0ea0e3959df2112e/1?pq-origsite=gscholar&cbl=2041946

Qualitative identification of food materials by complex refractive index mapping in the terahertz range

Shin, Hee Jun, Sung-Wook Choi, and Gyeongsik Ok. "Qualitative identification of food materials by complex refractive index mapping in the terahertz range." Food Chemistry (2017).

Abstract

We investigated the feasibility of qualitative food analysis using complex refractive index mapping of food materials in the terahertz (THz) frequency range. We studied optical properties such as the refractive index and absorption coefficient of food materials, including insects as foreign substances, from 0.2–1.3 THz. Although some food materials had a complex composition, their refractive indices were approximated with effective medium values, and therefore, they could be discriminated on the complex refractive index map. To demonstrate food quality inspection with THz imaging, we obtained THz reflective images and time-of-flight imaging of hidden defects in a sugar and milk powder matrix by using time domain THz pulses. Our results indicate that foreign substances can be clearly classified and detected according to the optical parameters of the foods and insects by using THz pulses.

... 2.4. Reflective THz imaging setup. A reflective-mode THz-TDS was used in our experiment. The THz images of samples were obtained by using a two-dimensional scanning module on the THz-TDS (TPS-3000, Teraview, UK) (see Fig. S3(a) of the supplementary material). ...

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http://www.sciencedirect.com/science/article/pii/S0308814617316874

A non-destructive method for quality control of the pellet distribution within a MUPS tablet by terahertz pulsed imaging

Novikova, Anna, Daniel Markl, J. Axel Zeitler, Thomas Rades, and Claudia S. Leopold. "A non-destructive method for quality control of the pellet distribution within a MUPS tablet by terahertz pulsed imaging." European Journal of Pharmaceutical Sciences (2017).

Abstract

Terahertz pulsed imaging (TPI) was applied to analyse the inner structure of multiple unit pellet system (MUPS) tablets. MUPS tablets containing different amounts of theophylline pellets coated with Eudragit® NE 30 D and with microcrystalline cellulose (MCC) as cushioning agent were analysed. The tablets were imaged by TPI and the results were compared to X-ray microtomography. The terahertz pulse beam propagates through the tablets and is back-reflected at the interface between the MCC matrix and the coated pellets within the tablet causing a peak in the terahertz waveform. Cross-section images of the tablets were extracted at different depths and parallel to the tablet faces from 3D terahertz data to visualize the surface-near structure of the MUPS tablets. The images of the surface-near structure of the MUPS tablets were compared to X-ray microtomography images at the same depths. The surface-near structure could be clearly resolved by TPI at depths between 24 and 152 μm below the tablet surface. An increasing amount of pellets within the MUPS tablets appears to slightly decrease the detectability of the pellets within the tablets by TPI. TPI was shown to be a non-destructive method for the detection of pellets within the tablets and could resolve structures thicker than 30 μm. In conclusion, a proof-of-concept was provided for TPI as a method of quality control for MUPS tablets.

... 2.2.2. Terahertz Pulsed Imaging. Five MUPS tablets, one from each batch, were imaged with a commercial TPI system (TPI™ imaga 2000, TeraView, Cambridge, UK) which represents an automated tablet scanner. As shown in Fig. ...

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http://www.sciencedirect.com/science/article/pii/S0928098717305845

Terahertz electrodynamics and superconducting energy gap of NbN

Sim, Kyung Ik, Young Chan Jo, Taewoo Ha, Jong Hyeon Kim, Jae Hoon Kim, and Hirotake Yamamori. "Terahertz electrodynamics and superconducting energy gap of NbN." Journal of the Korean Physical Society 71, no. 9 (2017): 571-574.

We have measured the transmission spectra of the conventional Bardeen-Cooper-Schrieffer (BCS) superconductor niobium nitride (NbN) thin films (Tc = 11 K) using terahertz time-domain spectroscopy (THz-TDS) over the spectral range of 10 - 110 cm −1 and the temperature range of 3.9 - 295 K. We extracted both the real part, σ1, and the imaginary part, σ2, of the optical conductivity, σ̃ = σ1 + iσ2, independently and simultaneously, without a Kramers-Kronig analysis. The superconducting gap Δ(T) was observed in the real part of the conductivity, σ1, below Tc = 11 K with a maximum value of 2Δ(0) = 30 cm −1 and the gap ratio 2Δ(0)/kBTc = 3.92.

... Terahertz transmission spectroscopy was performed with TeraView TPS-3000 Pulse Spectrometer over the frequency range of 2 - 120 cm −1 . The reliable spectral ...

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For full paper see

https://link.springer.com/article/10.3938/jkps.71.571

Biomedical Applications of Terahertz Imaging and Spectroscopy

Feature issue in Biomedical Optics Express

Biomedical Applications of Terahertz Imaging and Spectroscopy

Submission Opens: 1 September 2017

Submission Deadline: 15 November 2017

Biomedical Optics Express will publish a feature issue covering topics in biomedical applications of terahertz imaging and spectroscopy. The scope of the issue encompasses fundamental research, technology development, biomedical studies and clinical applications. The focus will be on:

• THz imaging and spectroscopy of tissues (ex vivo, in vivo, skin, breast, burns)
• Effects of high THz fields on biomedical samples
• Novel THz near-field imaging and spectroscopy
• THz combined with other techniques
• Molecular imaging and therapies
• Microfluidic THz devices
• Ophthalmology
• Gas sensing e.g. exhaled breath analysis
• Protein Spectroscopy
• Pharmaceutical Science e.g. dry dissolution testing

All papers need to present original, previously unpublished work and will be subject to the normal standards and peer-review processes of the journals. Submissions are encouraged from all areas of THz imaging and spectroscopy, but the main novelty is expected to be in biomedical applications. The standard Biomedical Optics Express publication charges will apply to all published articles.

Authors are encouraged to include acceptable supplementary materials (visualizations, tabular data, data sets, design files, or code). Please see OSA's guidelines on supplemental material.

To be eligible for publication, submissions that are based on a conference paper must add substantial and/or significant new information to the original conference summary, in accordance with OSA's Policy on Conference Papers.

Manuscripts must be prepared according to the usual standards for submission to Biomedical Optics Express and must be uploaded through OSA's electronic submission system, specifying from the drop-down menu that the manuscript is for the Feature Issue on Biomedical Applications of Terahertz Imaging and Spectroscopy.

Feature Issue Editors

Vincent Wallace, University of Western Australia, Australia (Lead Editor)
Emma Pickwell-MacPherson, The Chinese University of Hong Kong, China
Zachary Taylor, University of California Los Angeles, USA

Terahertz spectroscopy of charge transport in films of pristine and doped single-wall carbon nanotubes

Gorshunov, B. P., E. S. Zhukova, JuS Starovatykh, M. A. Belyanchikov, A. K. Grebenko, A. V. Bubis, V. I. Tsebro et al. "Terahertz spectroscopy of charge transport in films of pristine and doped single-wall carbon nanotubes." Carbon (2017).

Abstract

Electrical transport mechanisms of 2D carbon nanotube networks are presently under intensive studies. The related experimental data are ambiguous and controversial. We report on terahertz-infrared spectra of optical conductivity and dielectric permittivity of thin transparent films composed of pristine and CuCl- or iodine-doped single-walled carbon nanotubes (SWCNTs) measured in the frequency range from 7 to 25 000 cm−1and at temperatures from 5 to 300 K. Controversially to the existing results, we have not observed a clear signature of the so-called terahertz conductivity peak. Instead, a typical metallic-like frequency- and temperature-dependent behavior of the conductivity and permittivity has been discovered. It was attributed to the high quality interconnected SWCNT network providing the almost free pathways for charge carriers. Applying Drude conductivity model, we have determined the temperature and doping dependences of effective parameters of the carriers in the films: plasma frequency, scattering rate, mobility, mean-free path. The obtained results demonstrate a great potential of the material in the field of electromagnetic applications at frequencies up to few terahertz.

... At terahertz frequencies, from ν ≈ 7 to 60 cm −1 , the spectra of real and imaginary parts of complex conductivity σ*(ν) = σ 1 (ν)+iσ 2 (ν) and dielectric permittivity ε*(ν) = ε′(ν)+iε"(ν) were registered with the TeraView time-domain spectrometer and the quasioptical ...

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For full paper see

http://www.sciencedirect.com/science/article/pii/S0008622317310722

A split-ring-resonator-based polarization-insensitive ultra broadband filter in terahertz range

Mei Zhu
Proceedings of the Nature Research Society,2017,1,01005
Published Online: 13 October 2017(Article)

Abstract

Split-ring-resonators (SRRs) are one of the most common unit cell designs for metamaterials. Though extensively studied and well understood, such devices are often used as narrow-band filters due to SRRs' sharp resonance to electromagnetic wave. In this work, based on the idea of patterning metal SRRs on both sides of a dielectric substrate while rotating patterns on one side 90o to the other, we show that simple circular SRR can be a building block for broadband filters in terahertz (THz) range. The design principle is detailed with simulation results, showing that such fabricated devices essentially equates to two narrow-band filters on both sides of the substrate connected in series. By changing the unit cell from single SRR to double SRR, we effectively expanded the stop band width of the broadband filter. Devices were created on two types of substrates, 1 mm thick quartz and 100 µm thick polyethylene terephthalate (PET), demonstrating the ease and wide applicability of the fabrication process, while a bandwidth of as large as 1.40 THz has been achieved.

... device are focused simultaneously. The EM responses of the devices were characterized using terahertz time domain spectroscopy (THz-TDS, TeraView TPS 3000) in transmission mode. The measured transmission spectra ...

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For full paper see

https://nrs.org/journal/pnrs/browse-the-journal/volume-1/a-split-ring-resonator-based-polarization-insensitive-ultra-broadband-filter-in-terahertz-range