Tuesday, 31 March 2015

The role of terahertz polariton absorption in the characterization of crystalline iron sulfate hydrates

Michael T. Ruggiero,   Tiphaine Bardon,   Matija Strlič,   Philip F. Taday and    Timothy M. Korter


Iron sulfate compounds have been used extensively to produce iron gall ink, a widely used writing ink in the western world from the 12th–20th centuries. Iron gall ink is well known to corrode writing supports, so detection of iron species is important for the preservation of historical artwork and documents. Iron(II) sulfate readily changes hydration states and oxidizes in ambient conditions, forming compounds that contribute to this deterioration. In this study, five forms of iron sulfate are characterized by terahertz spectroscopy and solid-state density functional theory (DFT). The results have revealed that the room temperature spectra of FeSO4·7H2O and FeSO4·4H2O are remarkably similar, differing by only a single absorption feature. The identifying terahertz spectra provide an unambiguous metric to determine the relative concentrations of the most common hydrates FeSO4·7H2O and FeSO4·4H2O in a mixed sample. Complete spectral assignments of these species were accomplished by quantum mechanical simulations, with the exception being a single anomalous feature at approximately 40 cm−1 in the heptahydrate. This peak is believed to be due to polariton absorption, brought about by the particular coordination structure of FeSO4·7H2O that results in a greater charge separation relative to the other iron sulfate crystals.

Wednesday, 25 March 2015

TeraView's Dr. Philip Taday at CLEO:2015

TeraView are happy to announce that Dr. Philip Taday will be attending CLEO:2015! 

'CLEO: Expo is sure to be exciting, filled with rare insights into the industry’s emerging applications and innovations. CLEO: Expo draws in customers and prospects from top institutions and corporations representing the fastest growing markets in optics and photonics worldwide. Make sure your company is there to experience it!'

Dr. Philip Taday will also be presiding over a technical session titled 'THz Spectroscopic Techniques' on the 12th of May from 4:00 PM to 6:00 PM in the executive ballroom (session code: STu4H). 

To arrange a chance to meet with Dr. Philip Taday be sure to make contact prior to the event via e-mail: philip.taday@teraview.com 

Monday, 23 March 2015

In vitro human serum albumin glycation monitored by Terahertz spectroscopy

Maria Mernea, Alina Ionescu, Ionut Vasile, Cristina Nica, Gheorghe Stoian, Traian Dascalu, Dan Florin Mihailescu


The nonenzymatic attachment of sugars to proteins, namely glycation, is accelerated under diabetic conditions. Monitoring the glycated human serum albumin (HSA) levels gives the short term variation of glucose concentration in diabetic patients blood. Therefore, a significant effort was made to measure glycated HSA, including by spectroscopic methods such as Raman. Here we used THz spectroscopy to monitor HSA glycation in time (over 5, 7 and 11 weeks). Different sugar types have different reactivity; therefore we also addressed the reducing sugar influence on glycation by performing in vitro HSA glycation by both glucose and fructose. Since residues protonation state influences their susceptibility for glycation, we incubated HSA with sugars at two pH values: 7 and 8. Our results show that THz absorption decreases with the incubation time of HSA with sugars. At the incubation times we considered, the most significant differences were obtained on HSA samples glycated using glucose. Differences between samples glycated by glucose and by fructose show that glycation by glucose is a slower process. At pH 7, glycation by glucose is slower than at pH 8, while glycation by fructose is slightly faster at pH 7 than at pH 8. Glycated HSA models with different degrees of glycation were built by molecular modeling. Simulated THz spectra of the models are in good agreement with the experimental data. All these show that THz spectroscopy could monitor the progression of glycation in time and that it is sensitive to reducing sugars or pH value used in the glycation process.

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

Thursday, 19 March 2015

Analysis of the Terahertz Absorption Spectrum of Melamine

Yeun Hee Hwang, Yo Han Noh, Dongkyun Seo, Hak Min Yeo, Seongheun Kim, Jaehun Park, Hyang Sook Chun, and Kyungwon Kwak


In this paper, with terahertz (THz) time-domain spectroscopy, we measure the characteristic absorption peaks of melamine and analyze their vibrational modes with the help of solid-state density functional theory (DFT) calculations. The observed strong absorption peaks at 2, 2.27, and 2.61 THz are well reproduced but show red shifts compared to the theoretical results. Detailed normal mode analyses are carried out, which reveals that those THz peaks are generated from intermolecular vibrations. Temperature-dependent THz measurements suggest that this red shift mainly comes from the temperature effect. Thus, three peaks are assigned to the calculated intermolecular vibrational motions. This result indicates that THz spectroscopy can be a useful tool to detect the details of intermolecular structures.

Wednesday, 18 March 2015

A Dielectric Model of Human Breast Tissue in Terahertz Regime

Truong, B.C.Q. ; Tuan, H.D. ; Fitzgerald, A.J. ; Wallace, V.P. ; Nguyen, H.T.


The double Debye model has been used to understand the dielectric response of different types of biological tissues at terahertz (THz) frequencies but fails in accurately simulating human breast tissue. This leads to limited knowledge about the structure, dynamics, and macroscopic behavior of breast tissue, and hence, constrains the potential of THz imaging in breast cancer detection. The first goal of this paper is to propose a new dielectric model capable of mimicking the spectra of human breast tissue's complex permittivity in THz regime. Namely, a non-Debye relaxation model is combined with a single Debye model to produce a mixture model of human breast tissue. A sampling gradient algorithm of nonsmooth optimization is applied to locate the optimal fitting solution. Samples of healthy breast tissue and breast tumor are used in the simulation to evaluate the effectiveness of the proposed model. Our simulation demonstrates exceptional fitting quality in all cases. The second goal is to confirm the potential of using the parameters of the proposed dielectric model to distinguish breast tumor from healthy breast tissue, especially fibrous tissue. Statistical measures are employed to analyze the discrimination capability of the model parameters while support vector machines are applied to assess the possibility of using the combinations of these parameters for higher classification accuracy. The obtained analysis confirms the classification potential of these features.

Tuesday, 17 March 2015

THz Transparent Metamaterials for Enhanced Spectroscopic and Imaging Measurements

Sanphuang, V. ;  Woon-Gi Yeo ; Volakis, J.L. ; Nahar, N.K.


We present a frequency-selective surfaces (FSS) transparent window exhibiting low losses for broadband spectroscopic and imaging measurements in terahertz (THz) frequencies. The intent is to replace existing samples holders (e.g., Z-cut crystal quartz) with transparent metamaterial windows and increase measurement sensitivity. To enable multiband and broadband responses, two designs of single-layer FSS with superstrate are demonstrated: circular slot and double square loop, and thus suppress losses in a given range of THz band.

Wednesday, 11 March 2015

USE of COC substrates for millimeter-wave devices

Iñigo Ederra and Ramon Gonzalo


This article discusses the use of cyclic olefin copolymer (COC) substrates for development of millimeter wave devices. The improvement of performance thanks to the low losses of these substrates is demonstrated using a millimeter-wave subharmonic mixer working at 220 GHz as test bench. Furthermore, it is the first time this substrate material is used for designing millimeter-wave components. Some of its main advantages versus conventional substrates are the low losses at high frequencies, the direct gold sputtering, and the robustness. The measured results show 300 K noise temperature and 0.5 dB conversion loss reduction with respect to those obtained by a similar subharmonic mixer developed on a Rogers substrate. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:371–377, 2015

Monday, 9 March 2015

Reconfiguration of Resonance Characteristics for Terahertz U-Shape Metamaterial Using MEMS Mechanism

Yu-Sheng Lin ; Chia-Yi Huang ; Chengkuo Lee


We present the design, simulation, fabrication, and characterization of an out-of-plane reconfiguration of terahertz (THz) U-shape metamaterial. The U-shape metamaterial is consisted of bilayer cantilevers with different coefficient of thermal expansion. The electromagnetic tunability of U-shape metamaterial is accomplished by using electrostatic actuation mechanism to provide higher tuning range at lower driving voltage. The bilayer cantilevers are actuated toward the substrate by gradually increasing the bias and, then, completely snapped down when the bias reached the critical pull-in voltage. Therefore, this device can control the resonant frequency actively. The experimental results indicate that the device possesses 0.51-THz tuning range with polarization dependence compared to dc bias of 0 and 12 V. Moreover, this device can be a THz switch when rotated to different angle with respect to the polarization of incident light. Hence, such adaptive metamaterial device offers significant potential in realizing the multifunctionality in optical filter, polarization controller, and optical switch applications.

Thursday, 5 March 2015

3-D-Printed Flat Optics for THz Linear Scanners

Siemion, A. ; Bieda, M.S. ; Blocki, N. ; Coquillat, D. ; Cywinski, G. ; Czerwinska, E. ; Doch, M. ; Kowalczyk, A. ; Palka, N. ; Sobczyk, A. ; Zagrajek, P. ; Zaremba, M. ; Kolodziejczyk, A. ; Knap, W. ; Sypek, M.


THz beam shaping via a single diffractive optical element is used to convert a divergent beam into a focal line segment perpendicular to the optical axis. The novel structure was designed for narrowband applications as a kinoform element and we successfully applied it in active, high-speed, THz linear scanners. The theoretical approach and experimental results are presented.

Wednesday, 4 March 2015

IRMMW-THz 2015 Abstract Reminder

Please be reminded to submit your abstract for IRMMW-THz 2015 via the online submission site at: http://www.irmmw-thz2015.org.

There are only 30 days remaining until the abstract submission deadline of 31st March!

NEW! Check out the Technical Program page to see our excellent line up of plenary speakers.

'The International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), is the oldest and largest continuous forum devoted to the science and technology of long-wavelength radiation. The scope of the conference includes all scientific and technological activities from millimeter-waves to the THz regime and on to the far-infrared region of the electromagnetic spectrum. This covers a very wide range of disciplines, encompassing everything from micro- and nano-scale devices and structures to large-scale accelerators and tokamaks and their applications. Presentations at this conference address issues ranging from basic physics, chemistry, electrical engineering and materials science to problems in high frequency circuits and systems, communications, antennas and optics, imaging and spectroscopy, and much, much more.
The conference brings together scientists and technologists from more than 30 countries and typically hosts 600-700 participants. Contributed papers are archived on IEEEXplore, and IEEE is a long term technical co-sponsor of the conference series - currently celebrating 40 years since the first event was held in Atlanta, Georgia in 1974.'

Tuesday, 3 March 2015

Double Fano resonances in a composite metamaterial possessing tripod plasmonic resonances

Y U Lee, E Y Choi, E S Kim, J H Woo, B Kang, J Kim, Byung Cheol Park, T Y Hong, Jae Hoon Kim and J W Wu


By embedding four-rod resonators inside a double-split ring resonator superlattice, a planar composite metamaterial possessing tripod plasmonic resonances is fabricated. Double Fano resonances are observed where a common subradiant driven oscillator is coupled with two superradiant oscillators. As a classical analogue of a four-level tripod atomic system, the extinction spectrum of the composite metamaterial exhibits a coherent effect based on double Fano resonances. Transfer of the absorbed power between two orthogonal superradiant oscillators is shown to be mediated by the common subradiant oscillator.

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