Tuesday, 30 June 2020
The OSA has awarded the William F. Meggers Award for recognition of his outstanding work in spectroscopy to Tony F. Heinz
Stanford University and SLAC National Accelerator Laboratory, USA
For seminal studies of the properties and dynamics of surfaces, interfaces, and nanoscale materials by diverse spectroscopic techniques, including through the development of powerful new methods .
Tony Heinz received a B.S. in physics from Stanford University, USA, and a Ph.D. in physics from the University of California, Berkeley, USA. He is a professor of applied physics and photon science at Stanford University and the Associate Laboratory Director for Energy Sciences at SLAC National Accelerator Laboratory. Previously, he was a research staff member at the IBM Watson Research Center, USA, and a professor of physics and electrical engineering at Columbia University, USA. He is a Fellow of OSA and served as OSA President in 2012. Heinz has developed a wide range of spectroscopic techniques to examine the properties and dynamics of nanoscale systems. These methods include interface sensitive nonlinear spectroscopy and time-resolved approaches, such as terahertz time-domain techniques. The measurement techniques have been applied to elucidate the electronic, optical and chemical properties of 0-, 1-, and 2-dimensional materials and interfaces. The research would not have been possible without the insight and hard work of more than 70 graduate students and postdocs over the years.
Monday, 29 June 2020
Influence of SiO2 nanoparticles on morphology, optical, and conductivity properties of Poly (ethylene oxide)
Hameed, Talaat A., F. Mohamed, A. M. Abdelghany, and G. Turky. "Influence of SiO."
In this work, a detailed insight to the microstructure, morphology, surface topography, electrical and optical properties in visible and terahertz range was presented for polyethylene oxide (PEO)/silicon dioxide SiO2 nanocomposites. PEO-filled with various contents of SiO2 nanoparticles were synthesized via the solution cast technique. The polycrystalline nature of PEO/SiO2 films was affirmed by the selected area electron diffraction pattern (SAED) recorded by HRTEM measurement and it was found to nearly conformable with X-ray diffraction data. The energy-dispersive X-ray analysis (EDAX) proved the existence of SiO2 with wt% ranged from 0 to 5% as starting fillers. The high-resolution scanning electron microscope planar images indicated uniform distribution of SiO2 nanoparticles within the PEO films. The atomic force microscope 3D images depicted the surface changed from rough to smooth upon the filling with SiO2. The composite samples exhibit absorption spectra that extended from UV–Vis to near infrared regions. Based on Tauc's formula, it was found that the absorption edge shifted from 4.90 to 3.20 eV as the filler fraction increased from 0 to 5 wt%. The analysis of reflective index in the UV–Vis–NIR regions displayed decrement with increasing filler content. Moreover, the refractive index in Vis–NIR regions is good extension to that in THz region expressing the optical quality of studied films. The optical dispersion parameters were analyzed in the view of Wemple-Didomenico single oscillator and Sellmeier model. The values of nonlinear optical parameters (nonlinear susceptibility χ(3) and nonlinear refractive index (n2) were influenced by the filler fractions. Upon the rise of filler content, the conductivity values show slightly decrement.
for full paper see https://link.springer.com/article/10.1007%2Fs10854-020-03591-5
Friday, 26 June 2020
Monitoring the role of enantiomers in the surface modification and adsorption process of polymers imprinted by chiral molecules: theory and practice
Woźnica, Marcin, Monika Sobiech, Norbert Pałka, and Piotr Luliński. "Monitoring the role of enantiomers in the surface modification and adsorption process of polymers imprinted by chiral molecules: theory and practice." Journal of Materials Science: 1-17.
The objective of this study was to explore the role of enantiomers in the surface modification and adsorption process of polymers imprinted by chiral molecules. Here, R-, S- and R/S-1-aminoindanes (TR, TS and TR/S) were used as the model template molecules. Optimization of synthetic protocols facilitated preselection of the most efficient composition for a molecularly imprinted polymer (MIP)— methacrylic acid-co-ethylene glycol dimethacrylate—with satisfactory specificity and an imprinting factor equal to 3. This polymer composition was used further to analyse the effect of configuration of the template on adsorption properties. The results showed preferable adsorption of R-enantiomer, TR in the R-MIP and S-enantiomer, TS in the S-MIP but revealed variations in the binding capacities of TR and TS in the R- and S-cavity (stereoselectivity factor; k = 1.66 to 1.22, respectively). The theoretically analysed binding energies (DEB) of both TR and TS in the R-cavity (DEB = - 506.14 to - 256.77 kcal mol-1 ) and S-cavity (DEB = - 302.42 to - 347.18 kcal mol-1 ) were in agreement with empirical data. Morphology and porosity analyses revealed the impact of the template molecule on the pore system of the MIP and control (a non-imprinted polymer), but enantiomers were only found to have a negligible role. Binding characterization revealed that the physisorption-governed adsorption process and Dubinin– Radushkevich model fitted the experimental data best. Finally, terahertz spectroscopy was employed to confirm the similarity between both materials imprinted by each enantiomer.
for full paper see https://link.springer.com/content/pdf/10.1007/s10853-020-04796-z.pdf
… Terahertz spectroscopy was performed at the Military University of Technology Institute
of Opto- electronics, Warsaw, Poland. A TDS-based spec- trometer was used for terahertz
measurements (Teraview TPS Spectra 300, Cambridge, UK) in transmission …
Thursday, 25 June 2020
Simultaneous Investigation of the Liquid Transport and Swelling Performance during Tablet Disintegration
Al-Sharabi, Mohammed, Daniel Markl, Theona Mudley, Prince Bawuah, Anssi-Pekka Karttunen, Cathy Ridgway, Patrick Gane et al. "Simultaneous Investigation of the Liquid Transport and Swelling Performance during Tablet Disintegration." International Journal of Pharmaceutics (2020): 119380.
Wednesday, 24 June 2020
Terahertz-infrared electrodynamics of swingle-crystalline Ba0. 2Pb0. 8Al1. 2Fe10. 8O19 M-type hexaferrite
Ahmed, Asmaa, Anatoly S. Prokhorov, Vladimir Anzin, Denis Vinnik, Alexander Bush, Boris Gorshunov, and Liudmila Alyabyeva. "Terahertz-infrared electrodynamics of swingle-crystalline Ba0. 2Pb0. 8Al1. 2Fe10. 8O19 M-type hexaferrite." Journal of Alloys and Compounds (2020): 155462.
Tuesday, 23 June 2020
A novel type of sub-lattice of the Jahn-Teller (JT) centers was arranged in Ti-doped barium hexaferrite BaFe12O19. In the un-doped crystal all iron ions, sitting in five different crystallographic positions, are Fe3+ in the high-spin configuration (S = 5/2) and have a non-degenerate ground state. We show that the electron-donor Ti substitution converts the ions to Fe2+ predominantly in tetrahedral coordination, resulting in doubly-degenerate states subject to the problem of the JT effect. The arranged JT complexes, Fe2+O4, their adiabatic potential energy, non-linear and quantum dynamics, have been studied by means of ultrasound and terahertz-infrared spectroscopies. The JT complexes are sensitive to external stress and applied magnetic field. For that reason, the properties of the doped crystal can be controlled by the amount and state of the JT complexes.
They used a terahertz time-domain spectrometer (Teraview TPS 3000 TDS)
Monday, 22 June 2020
Porosity, one of the important quality attributes of pharmaceutical tablets, directly affects the mechanical properties, the mass transport and hence tablet disintegration, dissolution and ultimately the bioavailability of an orally administered drug. The ability to accurately and quickly monitor the porosity of tablets during manufacture or during the manufacturing process will enable a greater assurance of product quality. This tutorial systematically outlines the steps involved in the terahertz-based measurement method that can be used to quantify the porosity of a tablet within seconds in a non-destructive and non-invasive manner. The terahertz-based porosity measurement can be performed using one of the three main methods, which are (i) the zero-porosity approximation (ZPA); (ii) the traditional Bruggeman effective medium approximation (TB-EMA); and (iii) the anisotropic Bruggeman effective medium approximation (AB-EMA). By using a set of batches of flat-faced and biconvex tablets as a case study, the three main methods are compared and contrasted. Overall, frequency-domain signal processing coupled with the AB-EMA method was found to be most suitable approach in terms of accuracy and robustness when predicting the porosity of tablets over a range of complexities and geometries. This tutorial aims to concisely outline all the necessary steps, precautions and unique advantages associated with the terahertz-based porosity measurement method.
for full paper see https://link.springer.com/article/10.1007/s10762-019-00659-0
Friday, 19 June 2020
Alves-Lima, Décio, Jun Song, Xiaoran Li, Alessia Portieri, Yaochun Shen, J. Axel Zeitler, and Hungyen Lin. "Review of Terahertz Pulsed Imaging for Pharmaceutical Film Coating Analysis." Sensors 20, no. 5 (2020): 1441.
Terahertz pulsed imaging (TPI) was introduced approximately fifteen years ago and has attracted a lot of interest in the pharmaceutical industry as a fast, non-destructive modality for quantifying film coatings on pharmaceutical dosage forms. In this topical review, we look back at the use of TPI for analysing pharmaceutical film coatings, highlighting the main contributions made and outlining the key challenges ahead.
for full paper see https://www.mdpi.com/1424-8220/20/5/1441
Thursday, 18 June 2020
We measure in a nondestructive and noncontact fashion the thicknesses of three scale films with thicknesses 28.5 ± 1.4 μm, 13.4± 0.9 μm, and 5.1 ± 0.3 μm on steel substrates employing terahertz time-of-flight tomography combined with advanced signal-processing techniques. Wüstite is the dominant phase in the scale films, though magnetite and hematite are also present. Because wüstite is electrically insulating, the incident terahertz electromagnetic pulses largely penetrate into the scale film; however, the pulses are entirely reflected by the underlying electrically conductive steel substrate. Because the film layers are thin, in some cases optically thin, the distinct pulses reflected at the air/scale and scale/steel interfaces overlap in time and thus are not visually evident in the reflected terahertz signal, necessitating the use of deconvolution techniques to recover the sample structure. We compare the merits of three deconvolution techniques, one unsuccessful (frequency-wavelet domain deconvolution) and two successful (sparse deconvolution and autoregressive extrapolation), to characterize the thicknesses of these scale films.
Wednesday, 17 June 2020
Vohra, Nagma, Tyler Bowman, Keith Bailey, and Magda El-Shenawee. "Terahertz Imaging and Characterization Protocol for Freshly Excised Breast Cancer Tumors." Journal of Visualized Experiments 158 (2020).
This manuscript presents a protocol to handle, characterize, and image freshly excised human breast tumors using pulsed terahertz imaging and spectroscopy techniques. The protocol involves terahertz transmission mode at normal incidence and terahertz reflection mode at an oblique angle of 30°. The collected experimental data represent time domain pulses of the electric field. The terahertz electric field signal transmitted through a fixed point on the excised tissue is processed, through an analytical model, to extract the refractive index and absorption coefficient of the tissue. Utilizing a stepper motor scanner, the terahertz emitted pulse is reflected from each pixel on the tumor providing a planar image of different tissue regions. The image can be presented in time or frequency domain. Furthermore, the extracted data of the refractive index and absorption coefficient at each pixel are utilized to provide a tomographic terahertz image of the tumor. The protocol demonstrates clear differentiation between cancerous and healthy tissues. On the other hand, not adhering to the protocol can result in noisy or inaccurate images due to the presence of air bubbles and fluid remains on the tumor surface. The protocol provides a method for surgical margins assessment of breast tumors.
Zhang, Ping, Shuncong Zhong, Junxi Zhang, Jian Ding, Zhenxiang Liu, Yi Huang, Ning Zhou, Walter Nsengiyumva, and Tianfu Zhang. "Application of Terahertz Spectroscopy and Imaging in the Diagnosis of Prostate Cancer." Current Optics and Photonics 4, no. 1 (2020): 31-43.
The feasibility of the application of terahertz electromagnetic waves in the diagnosis of prostate cancer was examined. Four samples of incomplete cancerous prostatic paraffin-embedded tissues were examined using terahertz spectral imaging (TPI) system and the results obtained by comparing the absorption coefficient and refractive index of prostate tumor, normal prostate tissue and smooth muscle from one of the paraffin tissue masses examined were reported. Three hundred and sixty cases of absorption coefficients from one of the paraffin tissues examined were used as raw data to classify these three tissues using the Principal Component Analysis (PCA) and Least Squares Support Vector Machine (LS-SVM). An excellent classification with an accuracy of 92.22% in the prediction set was achieved. Using the distribution information of THz reflection signal intensity from sample surface and absorption coefficient of the sample, an attempt was made to use the TPI system to identify the boundaries of the different tissues involved (prostate tumors, normal and smooth muscles). The location of three identified regions in the terahertz images (frequency domain slice absorption coefficient imaging, 1.2 THz) were compared with those obtained from the histopathologic examination. The tissue tumor region had a distinctively visible color and could well be distinguished from other tissue regions in terahertz images. Results indicate that a THz spectroscopy imaging system can be efficiently used in conjunction with the proposed advanced computer-based mathematical analysis method to identify tumor regions in the paraffin tissue mass of prostate cancer.
for full paper see https://www.osapublishing.org/copp/abstract.cfm?uri=copp-4-1-31
Terahertz Imaging and Spectroscopy Data Acquisition
All prostate tissue were tested using a TPI system (TeraPulse 4000, TeraView, Cambridge, England) operating in Reflection Spectrum and Imaging Module (RIM). This module adopts a single-point scanning imaging method. A raster-scanning system that changes the position of the sample through a mobile station in an X-Y plane was used, which allowed the terahertz radiation to pass through the individual points of the sample to be measured. The maximum size of the sample that the system can scan is 20 mm * 20 mm, and the minimum scanning step is 0.1 mm. The axial resolution of our TPI system used is around 30 microns and the maximum lateral resolution is around 250 microns. In this study, the scanning area of the sample was about 15 * 5 mm, the resolution of each point was 0.2 mm, and the diameter of the terahertz spot at the focal point is 0.2 mm
Monday, 15 June 2020
Wang, Qinghua, Bingtao Gao, Fatima Toor, Mark Arnold, and Hongtao Ding. "Laser process of transparent conducting surfaces for terahertz bandpass ultrathin metamaterials." In Laser-based Micro-and Nanoprocessing XIV, vol. 11268, p. 112680H. International Society for Optics and Photonics, 2020.
Terahertz (THz) optoelectronics have great potentials in communication, imaging, sensing and security applications. However, the state-of-the-art fabrication processes for THz devices are costly and time-consuming. In this work, we present a novel laser-based metamaterial fabrication (LMF) process for high-throughput fabrication of transparent conducting surfaces on dielectric substrates such as quartz and transparent polymers to achieve tunable THz bandpass filtering characteristics. The LMF process comprises two steps: (1) applying ultrathin-film metal deposition, with a typical thickness of 10 nm, on the dielectric substrate; (2) creating periodic surface pattern with a feature size of ~100 microns on the metal film using nanosecond pulsed laser ablation. Our results demonstrate the LMF-fabricated ultra-thin metal film exhibits newly integrated functionalities: (a) highly conductive with sheet resistance of ~20 Ω/sq; (b) optically transparent with visible transmittance of ~70%; (c) tunable bandpass filtering effect in the THz frequency range; and (d) extraordinary mechanical durability during repeated fatigue bending cycles. The scientific findings from this work will render an economical and scalable manufacturing technique capable of treating large surface area for multi-functional THz metamaterials.
for full paper see https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11268/112680H/Laser-process-of-transparent-conducting-surfaces-for-terahertz-bandpass-ultrathin/10.1117/12.2544054.short
… 2.5 THz Transmission Measurement Experimental THz transmission spectra, were generated using THz-Time Domain Spectroscopy (THz-TDS) technique 52,53. A 1000D TeraView spectrometer (TeraView Limited, Cambridge)
Friday, 12 June 2020
Abautret, Yannick, Dominique Coquillat, Myriam Zerrad, Ryad Bendoula, Gabriel Soriano, Daphné Héran, Bruno Grèzes-Besset, Frédéric Chazallet, and Claude Amra. "Optical thickness of a plant leaf measured with THz pulse echoes." In Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XIII, vol. 11279, p. 112790L. International Society for Optics and Photonics, 2020.
We analyze Terahertz (THz) echoes by reflection on a sunflower leaf in order to evaluate the internal leaf structure (geometry, complex indices and thicknesses). The analysis is based on the thin film multilayer formalism in time and frequency domains. A high agreement is emphasized between experiment and theory, and we evaluate how realistic the multilayer solution can be in regard to our knowledge related to the sunflower leaf. A test campaign is performed in Charles Coulomb laboratory, which is equipped with the THz spectrometer.
for full paper see https://www.spiedigitallibrary.org/conference-proceedings-of-spie/11279/112790L/Optical-thickness-of-a-plant-leaf-measured-with-THz-pulse/10.1117/12.2543710.short?SSO=1
… 2.1 Terahertz Time Domain Spectroscopy (TTDS) In this study we performed the measurements campaign on a Terapulse 4000 spectrometer (TeraView Ltd., Cambridge, UK) with a femto-second fibre laser light source and a …
Thursday, 11 June 2020
Mernea, Maria, Roxana Ulăreanu, Octavian Călboreanu, Gabriela Chiritoiu, Dana Cucu, and Dan Mihăilescu. "N-glycosylation state of TRPM8 protein revealed by terahertz spectroscopy and molecular modelling." Biochimica et Biophysica Acta (BBA)-General Subjects (2020): 129580.
TRPM8 member of the TRP superfamily of membrane proteins participates to various cellular processes ranging from Ca uptake and cold sensation to cellular proliferation and migration. TRPM8 is a large tetrameric protein with more than 70% of its residues located in the cytoplasm. TRPM8 is N-glycosylated, with a single site per subunit. This work focuses on the N-glycosylation of TRPM8 channel that was previously studied by our group in relation to proliferation and migration of tumoral cells. Here, experimental data performed with deglycosylating agents assess that the sole glycosylation site contains complex glycans with a molecular weight of 2.5 kDa. The glycosylation state of TRPM8 in cells untreated and treated with a deglycosylating agent was addressed with Terahertz (THz) spectroscopy. Results show a clear difference between cells comprising glycosylated and deglycosylated TRPM8, the first presenting an increased THz absorption. Human TRPM8 was modelled using as templates the available TRPM8 and other TRPM channels structures. Glycosylations were modelled by considering two glycan structures with molecular weight close to the experiment: shorter and branched at the first sugar unit (glc1) and longer and unbranched (glc2). Simulation of THz spectra based on the molecular dynamics of unglycosylated and the two glycosylated TRPM8 models in lipid membrane and solvation box showed that glycan structure strongly influences the THz spectrum of the channel and of other components from the simulation system. Only spectra of TRPM8 with glc1 glycans were in agreement with the experiment, leading to the validation of glc1 glycan structure.
for full paper see https://www.sciencedirect.com/science/article/abs/pii/S0304416520300854
… corresponding enzymes. 2.3. THz spectroscopy measurements. Transmission THz time-domain spectroscopy measurements were performed using a TPS Spectra 3000 spectrometer (TeraView Limited, Cambridge). The analysed …
Wednesday, 10 June 2020
Tuesday, 9 June 2020
Broadband amplitude, frequency, and polarization splitter for terahertz frequencies using parallel-plate waveguide technology.
Hernandez-Serrano, A. I., Daniel M. Mittleman, and Emma Pickwell-MacPherson. "Broadband amplitude, frequency, and polarization splitter for terahertz frequencies using parallel-plate waveguide technology." Optics Letters 45, no. 5 (2020): 1208-1211.
In this Letter, we report a broadband frequency/polarization
demultiplexer based on parallel-plate waveguides (PPWGs)
for terahertz (THz) frequencies. The fabrication and
experimental validation of this polarization sensitive
demultiplexer is demonstrated for the range from 0.2 to
1 THz. Upgrading the demultiplexer by adding a second
demultiplexer stage, a fifty-fifty amplitude splitter is also
demonstrated in the same frequency range. The multiplexer
is based on a stainless-steel traveling-wave antenna, exhibiting strong mechanical robustness. This unique device
exhibits three splitting mechanisms in the same device:
amplitude, polarization, and frequency splitting. This is
a significant improvement for the next generation of THz
passive components for communication purposes.
"To characterize the proposed demultiplexer, we use the
Terapulse 4000 THz-TDS spectrometer from TeraView Ltd.
with a spectral resolution of 4.5 GHz in the configuration shown
in Fig. 2. This setup allows for the angle variation between the
exit face of the demultiplexer and the receiver. An aperture size
of 2.5 mm is placed in front of the receiver in order to improve
the spatial resolution. In this Letter, we study two demultiplexers with two different values of the plate spacing in order to
highlight the tunability of the device. In Fig. 3, the experimental
results for the two demultiplexers are presented for both TE1
and TEM modes. "
Monday, 8 June 2020
Pan, Mingming, Quentin Cassar, Frédéric Fauquet, Georges Humbert, Patrick Mounaix, and Jean-Paul Guillet. "Guided terahertz pulse reflectometry with double photoconductive antenna." Applied optics 59, no. 6 (2020): 1641-1647.
Friday, 5 June 2020
Khaliduzzaman, Alin, Keiji Konagaya, Tetsuhito Suzuki, Ayuko Kashimori, Naoshi Kondo, and Yuichi Ogawa. "A nondestructive eggshell thickness Measurement technique Using terahertz Waves." Scientific reports 10, no. 1 (2020): 1-5.
Eggshells play a number of important roles in the avian and reptile kingdom: protection of internal contents and as a major source of minerals for developing embryos. However, when researching these respective roles, eggshell thickness measurement remains a bottleneck due to the lack of a non-destructive measurement techniques. As a result, many avian and reptile research protocols omit consideration of eggshell thickness bias on egg or embryo growth and development. Here, we validate a non-destructive method to estimate eggshell thickness based on terahertz (THz) reflectance spectroscopy using chicken white coloured eggs. Since terahertz waves are reflected from outer air-eggshell interface, as well as the inner eggshell-membrane boundary, the resulting interference signals depend on eggshell thickness. Thus, it is possible to estimate shell thickness from the oscillation distance in frequency-domain. A linear regression-based prediction model for non-destructive eggshell thickness measurement was developed, which had a coefficient of determination (R2) of 0.93, RMSEP of 0.009, RPD of 3.45 and RER 13.67. This model can estimate eggshell thickness to a resolution of less than 10 μm. This method has the potential to expand the protocols in the field of avian and reptile research, as well as be applied to industrial grading of eggs.
For full paper see https://www.nature.com/articles/s41598-020-57774-5
"The intact eggs were measured using terahertz time-domain spectroscopy (THz-TDS, model: TPS spectra 3000, TeraView Ltd., UK) shown in Fig. 3. The eggs were irradiated by a THz pulse with an incident angle of 13 degrees. Following this, the reflected time-domain signal from the egg was obtained and reflectance calculated using a Blackman-Harris window function18. We then performed a fast Fourier transformation (FFT)."
Thursday, 4 June 2020
Chopard, Adrien, J. Bou Sleiman, Q. Cassar, P. Fauché, J. P. Guillet, P. Mounaix, M. Pan, J. B. Perraud, and A. Susset. "Contactless Terahertz Paint Thickness Measurements: specificity of aeronautics industry." (2019).
We report on numerical developments for the analysis of multilayered structures and the extraction of individual layer properties obtained by terahertz time domain measurements. An iterative algorithm implements a connected propagation tree which denotes the occurrence of the incident pulse division for each reflection / transmission appearance at each interface encountered during the propagation. Each sub pulse is individually monitored and its carried proportion of the incident power is extracted. Such a process allows to obtain the specific dielectric properties of each layer but additionally permits to derive a parametric transfer function describing the whole interaction with an incident beam. Procedure results performed on aeronautics multilayered painting samples are reported.
for full paper see https://www.ndt.net/article/aero2019/papers/fp_we1a5_a_chopard.pdf
"The first step to achieve the simulations and the characterization, was to carefully extract the dielectric properties of each individual painting material (Tab. 1) via a basic inverse problem method thanks to measurements performed on a Teraview TPS 4000 system. Both the real and the imaginary part of the dielectric function are fitted with a first order Debye relaxation model. "
Wednesday, 3 June 2020
Yang, Xiaofan, Yonghu Zeng, Xiaoming Liu, Jun Zhou, Lu Gan, Hao Chen, and Junsheng Yu. "Low‐loss frequency selective surface for multi‐band THz transmission measurement." Microwave and Optical Technology Letters.
Tuesday, 2 June 2020
Huang, Shih-Ting, Shen-Fu Hsu, Kai-Yuan Tang, Ta-Jen Yen, and Da-Jeng Yao. "Application of a Terahertz System Combined with an X-Shaped Metamaterial Microfluidic Cartridge." Micromachines 11, no. 1 (2020): 74.
Terahertz (THz) radiation has attracted wide attention for its ability to sense molecular structure and chemical matter because of a label-free molecular fingerprint and nondestructive properties. When it comes to molecular recognition with terahertz radiation, our attention goes first towards the absorption spectrum, which is beyond the far infrared region. To enhance the sensitivity for similar species, however, it is necessary to apply an artificially designed metamaterial sensor for detection, which confines an electromagnetic field in an extremely sub-wavelength space and hence receives an electromagnetic response through resonance. Once the resonance is caused through the interaction between the THz radiation and the metamaterial, a minute variation might be observed in the frequency domain. For a geometric structure of a metamaterial, a novel design called an X-shaped plasmonic sensor (XPS) can create a quadrupole resonance and lead to sensitivity greater than in the dipole mode. A microfluidic system is able to consume reagents in small volumes for detection, to diminish noise from the environment, and to concentrate the sample into detection spots. A microfluidic device integrated with an X-shaped plasmonic sensor might thus achieve an effective and highly sensitive detection cartridge. Our tests involved not only measurements of liquid samples, but also the performance of a dry bio-sample coated on an XPS.
for full paper see https://www.mdpi.com/2072-666X/11/1/74
"The equipment for detection using THz time-domain spectroscopy (THz-TDS) is called a TeraPulse 4000 (product of TeraView, UK). The generation of terahertz pulsed radiation is based on a photoconductive switch in which terahertz photoconductive emitters rely on the production of fewcycle terahertz pulses using a femtosecond laser to excite a biased gallium arsenide antenna. This technique is inherently broadband, with the emitted power distributed over a frequency range from 60 GHz to 4 THz (wavenumber 2–133 cm−1 ). When demonstrating the measurement, the detection cartridge is installed at the fixed sample position in the chamber, as shown in Figure 3b. After setting up, the chamber is sealed and kept filled with dry air to eliminate any influence of water vapor. The spectrum"
Monday, 1 June 2020
EOTPR Electro Optical Terahertz Pulse Reflectometry: The world’s fastest and most accurate fault isolation system.
for more information see https://teraview.com/eotpr/#tab|1