Effect of swelling of a photoresist on electromagnetic resonance of terahertz metamaterials

Wei-Fan Chiang ; Yu-Ting Hsieh ; Song-Hang Wang ; Hsin-Yuan Miao ; Jih-Hsin Liu ; and Chia-Yi Huang

Abstract:

This work uses isopropyl alcohol (IPA) to develop a photoresist. IPA dissolves the photoresist that is not exposed to UV light, and swells the photoresist that is exposed to UV light. The swelling of the photoresist distorts the split-ring resonators (SRRs). The distorted SRRs have a larger loop length, smaller line width, and smaller split gap than undistorted SRRs. The change in the dimensions of the SRRs is caused by the extension of the SRR arms in their longitudinal directions. The resonance frequency of the distorted SRRs is smaller than that of the undistorted SRRs, and the resonance frequency decreases with the development time.

The resonance frequency of the distorted SRRs depends on not only their dimensions, but also the bending of their arms. The distorted SRRs in this work have a frequency tuning range with a maximum width of 0.13 THz. The method that is proposed herein uses IPA to fabricate passively tunable terahertz metamaterials, which exhibit the advantages of high reliability, low cost, and ease of fabrication.

Full article available here.

OMICS International Best Poster Award

TeraView would like to congratulate Dan Sporea, Laura Mihai, Adelina Sporea and Ion Vata on being presented with the Best Poster Award at the Third International Conference and Exhibition on Lasers, Optics and Photonics, for their paper entitled:

‘Testing of ZnSe, CaF₂, BaF₂ and sapphire windows under alpha particles irradiation’

Our TPS Spectra 3000 was used by the team to investigate IR materials under ionizing radiation exposure, and is the first time that such materials have been studied under alpha particle irradiation and Terahertz.

TeraView at EAS 2015

TeraView are pleased to announce their attendance at this year’s EAS Analytical Conference!

TeraView's Principal Scientist Dr. Philip Taday will be presenting a talk on Monday 16th November at 10.20am, by the title of:

‘Terahertz Systems for Cultural Heritage’

Tiphaine Bardon from UCL will follow the talk and present her work done in collaboration with TeraView using the TPS3000, titled:

‘Characterization and Imaging of Archival Texts: Let's Have a Word with Terahertz!’

If you would like to arrange a meeting with Dr. Philip Taday at EAS 2015, please contact him via philip.taday@teraview.com.

For more information on the event visit the EAS website here, and to view the program use this link.

The Eastern Analytical Symposium and Exposition (EAS) is held each year to provide professional scientists and students continuing education in the analytical and allied sciences through the presentation of symposia of papers, workshops, and short courses. An exposition of apparatus and supplies allied to these sciences is held concurrently with the symposia. 

EAS 2015 will be held November 16-18, 2015 at the Garden State Exhibit Center and hotel complex in Somerset, New Jersey.

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

Quad-band THz frequency selective surface based on a split ring resonator loaded with multiple slots

Abstract

A quad-band terahertz (THz) frequency selective surface with bandstop response is designed, fabricated, and characterized. The unit cell of the filter consists of a split ring resonator (SRR) and surrounding four groups of slots. Each group of slots has three slots with different lengths. The lowest frequency band is determined by the resonance of the SRR and the other three upper bands are selected by the resonance of the slots which exhibit bandstop characteristics rather than bandpass characteristics. The filter transformation characteristic originates from the slits placed between the unit cells which act as series-connected capacitive components. The fabricated quad-band THz filters exhibited bandstop characteristics with attenuation higher than 20 dB in all the operating frequency bands.

The quad-band FSSs were characterized using TeraView's time domain spectroscopy system - the TPS Spectra 3000.

http://www.tandfonline.com/doi/abs/10.1080/09205071.2015.1053576

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.

TeraView TPS 3000 unit for time domain spectroscopy was used to investigate spectral properties of nematic liquid crystal mixtures

Article

Spectral Properties of Nematic Liquid Crystal Mixtures Composed with Long and Short Molecules in THz Frequency Range

ABSTRACT In this paper the influence of short and long molecules added to liquid crystal
6CHBT were investigated. Change of refractive indices and absorption coefficients
for 6CHBT mixtures were compared in the 0.3 - 3 THz frequency range. Influence of
temperature on the mentioned parameters of liquid crystal were investigated. Our study
show that even a slight change in shape and the composition of the molecules dopants
affects the macroscopic properties of liquid crystal. These properties depend on the
length of chains, the number of benzene or cyclohexane rings or the spatial distribution
of molecules and the interactions between them in the liquid crystal mixture. Spectra
measurements on the terahertz time-domain spectrometer were performed.
Spectral Properties of Nematic Liquid Crystal Mixtures Composed with Long and Short Molecules in THz Frequency Range (PDF Download Available). Available from: http://www.researchgate.net/publication/235218799_Spectral_Properties_of_Nematic_Liquid_Crystal_Mixtures_Composed_with_Long_and_Short_Molecules_in_THz_Frequency_Range [accessed Jun 23, 2015].

Computationally Assisted (Solid-State Density Functional Theory) Structural (X-ray) and Vibrational Spectroscopy (FT-IR, FT-RS, TDs-THz) Characterization of the Cardiovascular Drug Lacidipine

Kacper Drużbicki, Jadwiga Mielcarek, Anna Kiwilsza, Loic Toupet, Eric Collet, Aleksandra Pajzderska, and Jan Wąsicki

Abstract

The structural properties of a second-generation dihydropyridine calcium antagonist, lacidipine, were explored by combining low-temperature X-ray diffraction with optical vibrational spectroscopy and periodic density functional theory (PBC DFT) calculations. Crystallographic analysis cannot discriminate between two possible molecular symmetries in crystals made of pure lacipidine: the space group Ama2, where the lacipidine molecule lies on mirror symmetry, or a Cc space group with distorted lacipidine molecules. Intermolecular interactions analysis reveals an infinite net of moderate-strength N–H···O hydrogen-bonds, which link the molecular units toward the crystallographic b-axis. Weak interactions were identified, revealing their role in stabilization of the crystal structure. The vibrational dynamics of lacidipine was thoroughly explored by combining infrared and Raman spectroscopy in the middle- and low-wavenumber range. The given interpretation was fully supported by state-of-the-art solid-state density functional theory calculations (plane-wave DFT), giving deep insight into the vibrational response and providing a complex assignment of spectral features. The vibrational analysis was extended onto the lattice-phonon range by employing time-domain terahertz spectroscopy. Analysis of the anisotropic displacement parameters suggests noticeable dynamics of the terminal (tert-butoxycarbonyl)vinyl moiety. The terahertz study provides direct experimental evidence of “crankshaft” type motions in the terminal chain. By combining low-wavenumber vibrational spectroscopy with the first-principles calculations, we were able to prove that the quoted thermodynamically stable phase corresponds to the monoclinic Cc space group.

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

Full Article: http://pubs.acs.org/doi/abs/10.1021/acs.cgd.5b00251

Passive imaging of concealed objects in terahertz and long-wavelength infrared

Marcin Kowalski, Mariusz Kastek, Michal Walczakowski, Norbert Palka, and Mieczyslaw Szustakowski

Abstract

Terahertz and infrared radiation have unique properties applicable to the field of surveillance and security systems. We investigated the possibility of detecting potentially dangerous objects covered by various types of clothing using passive imagers operating at 1.2 mm (250 GHz) and long-wavelength infrared at 6–15 μm (20–50 THz). We developed a measurement methodology that assumes to investigate theoretical limitations, performance of imagers, and physical properties of fabrics. To evaluate stability of the detection capabilities of imagers, we performed measurement sessions each lasting 30 min. We present a theoretical comparison of the two spectra and results of experiments using state-of-the-art equipment.

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

Full Article: http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-54-13-3826

Comparison of damage behaviour of different plant fibre composites under laser impact loading

F. Touchard, L. Berthe, P. Malinowski, S. Opoka, M. Boustie, L. Chocinski-Arnault and W. Ostachowicz

Abstract

The high strain rate behaviour of the eco-composites, when submitted to laser impact loading, is not well known yet. Crucial questions are still open: influence of plant fiber length and distribution on the composite impact behaviour, types of damage induced by impact loading, the way the failure occurs, etc. We present the very first results of a collaborative research involving the institutions PPRIME- Poitiers and PIMM-Paris, and IMP PAN-Gdansk-Poland. A comparison of laser shock induced damage is realised, based on observations of sample back faces for several types of eco-composites. Spallation, residual blister and inside delamination, depending on the fibre length in tested composites have been observed. The ability of the Terahertz technique for internal damage detection is demonstrated.

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

Full Article: http://www.mattech-journal.org/articles/mattech/abs/2015/01/mt150022/mt150022.html

Terahertz single conductance quantum and topological phase transitions in topological insulator Bi2Se3 ultrathin films

Byung Cheol Park, Tae-Hyeon Kim, Kyung Ik Sim, Boyoun Kang, Jeong Won Kim, Beongki Cho, Kwang-Ho Jeong, Mann-Ho Cho & Jae Hoon Kim

Abstract

Strong spin-orbit interaction and time-reversal symmetry in topological insulators generate novel quantum states called topological surface states. Their study provides unique opportunities to explore exotic phenomena such as spin Hall effects and topological phase transitions, relevant to the development of quantum devices for spintronics and quantum computation. Although ultrahigh-vacuum surface probes can identify individual topological surface states, standard electrical and optical experiments have so far been hampered by the interference of bulk and quantum well states. Here, with terahertz time-domain spectroscopy of ultrathin Bi2Se3 films, we give evidence for topological phase transitions, a single conductance quantum per topological surface state, and a quantized terahertz absorbance of 2.9% (four times the fine structure constant). Our experiment demonstrates the feasibility to isolate, detect and manipulate topological surface states in the ambient at room temperature for future fundamental research on the novel physics of topological insulators and their practical applications.

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

Full Article: http://www.nature.com/ncomms/2015/150316/ncomms7552/full/ncomms7552.html#figures

Temperature evolution of dielectric response spectra of stillwellite-like glasses in the terahertz and infrared ranges

G. A. Komandin, O. E. Porodinkov, Yu. G. Goncharov, I. E. Spektor, L. D. Iskhakova, V. N. Sigaev, S. V. Lotarev, V. I. Torgashev

Abstract

The reflectance and transmittance spectra of the PrBGeO5 glass were measured in the terahertz and infrared ranges. At low temperatures, an increase in the permittivity and the appearance of narrow resonance-type lines in the terahertz range were revealed. The complex permittivity spectra were calculated from the Fresnel and Kramers-Kronig formulas.

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

Full Article: http://link.springer.com/article/10.1134/S106378341406016X

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

Abstract

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)

Full Article: http://link.springer.com/article/10.1007/s11082-015-0129-y

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

Abstract

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.

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

Full Article: http://onlinelibrary.wiley.com/doi/10.1002/bkcs.10166/abstract?systemMessage=Wiley+Online+Library+will+be+disrupted+on+7th+March+from+10%3A00-13%3A00+GMT+%2805%3A00-08%3A00+EST%29+for+essential+maintenance.++Apologies+for+the+inconvenience.&userIsAuthenticated=false&deniedAccessCustomisedMessage

THz Transparent Metamaterials for Enhanced Spectroscopic and Imaging Measurements

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


Abstract

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.

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

Full Article: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6939743&contentType=Journals+%26+Magazines

Polarization-insensitive metamaterial absorber of selective response in terahertz frequency range

B Grześkiewicz, A Sierakowski, J Marczewski, N Pałka and E Wolarz

Abstract

We present an experimental and numerical analysis of a planar metamaterial that selectively absorbs terahertz radiation. The metamaterial is produced as a planar two-dimensional network of electromagnetic resonators and is characterized by electric and magnetic responses in a narrow frequency range. The unit cell of the metamaterial has fourfold symmetry about the axis perpendicular to the planes containing the metallic resonators. Such a planar metamaterial is polarization-insensitive to the electromagnetic waves. A good agreement of the absorption characteristics obtained from the numerical simulations and from the spectroscopic experiments is shown. The analysis of wave impedance, refractive index, permittivity and permeability of the metamaterial allows the identification of the characteristic electromagnetic resonance and antiresonance in the system. It is shown that the absorption is mostly the result of the electric field energy accumulation in the metamaterial absorber.

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

Full Article: http://iopscience.iop.org/2040-8986/16/10/105104

Complementary optical and neutron vibrational spectroscopy study of bromanilic acid: 2,3,5,6-tetramethylpyrazine (1:1) cocrystal

Katarzyna Łuczyńska, , Kacper Drużbicki, Krzysztof Lyczko, Wojciech Starosta

Abstract

Complementary structural and vibrational spectroscopy study of bromanilic acid:2,3,5,6-tetramethylpyrazine (BrA:TMP) 1:1 cocrystal is reported. The crystallographic structure was determined by means of single-crystal X-ray diffraction and can be described as a stacked net of hydrogen-bonded TMPH⁺⋯BrA⁻⋯BrA⁻⋯TMPH⁺ moieties. The structural analysis was supported by ¹³CP/MAS NMR study. The complementary vibrational analysis was performed by combining optical (infrared, Raman, terahertz) and inelastic neutron scattering spectroscopy with the state-of-the-art solid–state density functional theory (DFT) computations, which have proven to be superior to the hybrid cluster modeling approach. An excellent agreement between theoretical and experimental data was observed over the entire spectral range, allowing for deep understanding of the vibrational properties. While the primary hydrogen-bonding interactions are limited to the above quoted structural units, the system revealed very little dispersion of the phonon branches, manifested mainly in the intermolecular vibrations range. Moreover, the studied phase does not exhibit any mechanical instability, which could suggest a displacive structural transformation tendency.

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

Full Article: http://www.sciencedirect.com/science/article/pii/S0924203114001556

Polarization independent broadband terahertz antireflection by deep-subwavelength thin metallic mesh

Lu Ding*, Qing Yang Steve Wu andJing Hua Teng*

Abstract

Broadband antireflection coatings for passive terahertz (THz) components are extremely important in the application of THz technology. Metallic nano-films are commonly used for this purpose. Here a new approach to realize polarization independent broadband antireflection in THz range, based on a meta-surface design is experimentally demonstrated. The internal reflection of a broadband THz pulse (spectral bandwidth of 0.06 – 4 THz) at a Si/air interface can be fully suppressed with a Cr square mesh with deep-subwavelength dimensions. Small nonuniformity of the meta-surface structure can enhance the tolerance on structural parameters for achieving the AR condition. The design concept is applicable to other metals and frequency ranges as well, which opens a new window for future AR coatings.

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

Full Article: http://onlinelibrary.wiley.com/

Terahertz time-domain spectroscopy for measurement of particle sizes of fexofenadine hydrochloride

Anna Sadloňová, Vojtech Kresalek, Tomas Bata

Abstract

Time domain spectroscopy is one of the new methods of terahertz radiation used for wide spectrum of the industry. More extended sector is the security system much like the sector of the medicine. The main focus is orientated to detection and identification of the substances. This study is focused on the measurement of the particle size of pharmaceuticals. The characteristic absorption features will be studied experimentally by Terahertz time-domain spectroscopy. The results are identified for processing by one of the statistical method usable for such variable groups. The three samples of the pharmaceutical– Fexofenadine Hydrochloride (antihistamine) will be compared between themselves. Mentioned samples are supplied by different suppliers. The main focus will be put on the pharmaceutical differences of the same pharmaceutical that are commonly available on the markets. Terahertz time-domain spectroscopy setup was used to measure absorbance spectra of each sample in the range from 1 THz to 3 THz (it was used the device TPS Spectra 3000 produced by TeraView Ltd . The device that belongs to the first commercial machine developed in this company for measurement of the substances by transmission spectroscopy method.). During the testing was used the vacuum for purging the measurement chamber from water vapors.

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

Split-ring resonators manufactured on conductive layer by selective laser ablation

Paweł Koziol ; Arkadiusz J. Antończak ; Patrycja E. Szymczyk ; Bogusz Stępak ; Łukasz Łazarek ; Michał R. Wójcik ; Michał Walczakowski ; Krzysztof M. Abramski

Abstract

In this paper an alternative method of manufacturing SRR structures through the selective removal of a thin layer of silver-palladium deposited on the surface of the Al2O3 ceramic by laser ablation process using nanosecond Nd:YAG laser (1064 nm) was presented. The SRR structures array were subject to transmittance measurements using the TDS (Time Domain Spectroscopy). Both electric and magnetic resonances were observed at frequencies determined by the structural parameters of the SRR. In case of the E field perpendicular to an SRR structure and one resonance area for 0.56 THz with the E field parallel to the structure, two characteristic resonant dips for 0.31 THz and 0.62 THz were obtained. Studies have confirmed that using selective laser removal process enables the preparation of the resonant structure in the range of THz. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.


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

Full Article: http://www.sciencedirect.com/science/article/pii/S0939641114002203