Impact of Processing Conditions on Inter-tablet Coating Thickness Variations Measured by Terahertz In-Line Sensing

HUNGYEN LIN, ROBERT K. MAY, MICHAEL J. EVANS, SHUNCONG ZHONG, LYNN F. GLADDEN, YAOCHUN SHEN,

J. AXEL ZEITLER

Abstract

A novel in-line technique utilising pulsed terahertz radiation for directmeasurement of the film coating thickness of individual tablets during the coating process was previously developed and demonstrated on a production-scale coater. Here, we use this technique to monitor the evolution of tablet film coating thickness and its inter-tablet variability during the coating process under a number of different

process conditions that have been purposefully induced in the production-scale coating process. The changes that were introduced to the coating process include removing the baffles from the coater, adding uncoated tablets to the running process, halting the drum, blockage of spray guns and changes to the spray rate. The terahertz sensor was able to pick up the resulting changes in average coating thickness in the coating drum and we report the impact of these process changes on the resulting coating quality. C⃝ 2015 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci

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

Full Article: http://onlinelibrary.wiley.com/doi/10.1002/jps.24503/full

An Effective Method for Substance Detection Using the Broad Spectrum THz Signal with a “Terahertz Nose”

Vyacheslav A. Trofimov  and Svetlana A. Varentsova 

Abstract

We propose an effective method for the detection and identification of dangerous substances by using the broadband THz pulse. This pulse excites, for example, many vibrational or rotational energy levels of molecules simultaneously. By analyzing the time-dependent spectrum of the THz pulse transmitted through or reflected from a substance, we follow the average response spectrum dynamics. Comparing the absorption and emission spectrum dynamics of a substance under analysis with the corresponding data for a standard substance, one can detect and identify the substance under real conditions taking into account the influence of packing material, water vapor and substance surface. For quality assessment of the standard substance detection in the signal under analysis, we propose time-dependent integral correlation criteria. Restrictions of usually used detection and identification methods, based on a comparison between the absorption frequencies of a substance under analysis and a standard substance, are demonstrated using a physical experiment with paper napkins. 

Full Article: http://scholar.google.co.uk/scholar_url?url=http://www.mdpi.com/1424-8220/15/6/12103/pdf&hl=en&sa=X&scisig=AAGBfm1LSPK_lrl8QysLaqcq1c3X8gkORg&nossl=1&oi=scholaralrt

A Design of Terahertz Broadband Filters and Its Effect in Eliminating Asymmetric Characteristics in Device Structures

Zhu, M. ; Lee, C.

Abstract

We report a straightforward way to design and fabricate polarization-insensitive broadband bandstop filters in terahertz range by fabricating identical metal patterns on both sides of a dielectric substrate with one layer rotated 90o to the other. The unit cells used in such designs are the well-studied split-ring-resonators, hence the frequency range of the stop band can be easily tuned by varying the dimensions of the unit cell structures. Through simulation analysis, we show that such fabrication method requires no alignment in lithography step and works with common dielectric substrates. Two types of substrates, 1 mm-thick quartz and 100 μm-thick polyethylene terephthalate, were used as a demonstration. The transmission level stayed below 12% for a stopband of 0.42 THz frequency range. Lastly, we reasoned with simulation results that the proposed broadband filters give consistent performance regardless of the gap location in the unit cell, which will further extend their use in practical applications.

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

Full Article: http://ieeexplore.ieee.org/xpl/abstractAuthors.jsp?tp=&arnumber=7105824&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D7105824

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

Experimental (X-Ray, IR, RS, INS, THz) and Solid-State DFT Study on (1:1) Co-crystal of Bromanilic Acid and 2,6-Dimethylpyrazine

Katarzyna Łuczyńska , Kacper Drużbicki , Krzysztof Lyczko , and Jan Czeslaw Dobrowolski

Abstract

A combined structural, vibrational spectroscopy and solid-state DFT study of hydrogen-bonded complex of bromanilic acid with 2,6-dimethylpyrazine is reported. The crystallographic structure was determined by means of low-temperature single-crystal X-ray diffraction, which reveals the molecular units in their native protonation states, forming one-dimensional infinite nets of moderate-strength O∙∙∙H-N hydrogen bonds. The nature of the crystallographic forces, stabilizing the studied structure, has been drawn by employing the non-covalent interactions analysis. It was found that in addition to the hydrogen bonding, the intermolecular forces are dominated by stacking interactions and C-H∙∙∙O contacts. The thermal and calorimetric analysis was employed to probe stability of the crystal phase. The structural analysis was further supported by computationally assisted 13C CP/MAS NMR study, providing a complete assignment of the recorded resonances. The vibrational dynamics was explored by combining the optical (IR, Raman, TDs-THz) and inelastic neutron scattering (INS) spectroscopy techniques with the state-of-the-art solid-state density functional theory (DFT) computations. Despite of quasi-harmonic approximation assumed throughout the study, an excellent agreement between the theoretical and experimental data was achieved over the entire spectral range, allowing for deep and possibly thorough understanding of the vibrational characteristics of the system. Particularly, the significant influence of the long-range dipole coupling on the IR spectrum has been revealed. Based on a wealth of information gathered, the recent implementation of dispersion-corrected linear-response scheme has been extensively examined.

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

Full Article: http://pubs.acs.org/doi/abs/10.1021/acs.jpcb.5b03279

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

Continuously tunable and fast-response terahertz metamaterials using in-plane switching dual-frequency liquid crystal cells

Chia-Yi Huang, Chia-Chun Chen, Wei-Fan Chiang, Min-Cheng Tsai, Shun-An Jiang, Tsung-Hao Chang, and Song-Hang Wang

Abstract

A metamaterial that is embedded into an in-plane switching dual-frequency liquid crystal cell is used to develop an electrically controllable terahertz metamaterial. The resonance peak of the metamaterial can be redshifted and blueshifted as the frequency of an external voltage is switched, and the response times for the redshift and blueshift are 1.044 ms and 1.376 ms, respectively. A simulation confirms the spectral redshift and blueshift. The variation in the peak frequency as a function of applied frequency at the external voltage is presented. Experimental results show that the resonance peak of the metamaterial can be continuously tuned within a frequency range of 15 GHz as the applied frequency is switched between 19 kHz and 22 kHz. Therefore, this metamaterial is a continuously tunable and fast-response terahertz filter and could be used for terahertz imaging and terahertz telecommunications.

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

Full Article: http://www.opticsinfobase.org/ol/upcoming_pdf.cfm?id=235253

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

Quantification of residual crystallinity of ball-milled, commercially available, anhydrous β-lactose by differential scanning calorimetry and terahertz spectroscopy

Geoff Smith, Amjad Hussain, Nadeem Irfan Bukhari, Irina Ermolina

Abstract

The quantification of crystallinity is necessary in order to be able to control the milling process. In this study, the changes in the amount of residual crystallinity of ball-milled anhydrous β-lactose (β-LA), for periods up to 60 min, were evaluated by differential scanning calorimetry (DSC) and by terahertz pulsed spectroscopy. The percentage of residual crystallinity using DSC was estimated by two methods: The first method was based on the measurement of the melting of the crystalline part, while the second was based on the measurement of the devitrification of the amorphous part. Peaks in THz spectra, related to the residual crystalline material were analyzed by two methods: (1) area under peak and (2) partial least square. The milled samples of β-LA show a monotonic decrease in crystallinity with milling time, although the quantitative analysis performed by different techniques reveals very different results. THz technique gives significantly lower estimates for % crystallinity (in the early time period) than that calculated from the DSC data, possibly because of the recrystallization of amorphous form during sample preparation. The comparison of residual crystallinity of β-LA with its hydrated counterpart [i.e., α-lactose monohydrate (α-LMH)] has shown that the amount of amorphous material produced from the α-LMH is 20–30 % greater than from β-LA at extended milling times (i.e. 60 min).

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

Full Article: http://link.springer.com/article/10.1007%2Fs10973-015-4469-4

Comparisons of intra-tablet coating variability using DEM simulations, asymptotic limit models, and experiments

Ben Freireich, Rahul Kumar, William Ketterhagen, Ke Su, Carl Wassgren, J. Axel Zeitler

Abstract

Discrete element method (DEM) computer simulations are used to investigate intra-tablet coating thickness variability. Two new post-processing algorithms are presented. The first algorithm uses an image-based method to track the exposure to a simulated spray of small area panels on each tablet's surface so that the distribution of spray exposure times over the tablet's surface can be determined directly from DEM data. The second algorithm predicts the asymptotic limit of intra-tablet coating uniformity. This second algorithm includes the influence of tablet orientation and shadowing when considering exposure to the spray, averaged over many tablets.

The DEM simulations produce the first direct evidence that non-spherical tablets approach asymptotic intra-tablet coating variability values. The asymptotic limits are predicted well using the new asymptotic prediction model. In general, tablet caps have thicker coatings than tablet bands. Moreover, tablets that have a more elongated shape tend to have less coating on the smaller radius of curvature portions of the bands. Of particular importance in this new asymptotic modeling approach is the inclusion of shadowing effects. When shadowing is not included and only tablet orientation is considered, the predictions over-predict the asymptotic intra-tablet coating variability values and also change the observed rank order of the asymptotic values for different tablet shapes. The asymptotic intra-tablet coating variability values using the new algorithm correlate reasonably well with tablet sphericity, with increasing sphericity improving coating uniformity.

This paper also presents the first attempt to directly compare experimental and simulated coating thickness distributions. The asymptotic coating thickness predictions compare well qualitatively with terahertz thickness measurements made on tablets from coating experiments. Unfortunately, only qualitative comparisons could be made due to the limited number of tablets sampled experimentally and differences in spray zone areas and flux distributions. The tablets in the experiments, however, displayed similar features as those found in the simulations.

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

Full Article: http://www.sciencedirect.com/science/article/pii/S0009250915001852

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

Facile metal transfer method for fabricating unconventional metamaterial devices

Mei Zhu and Chengkuo Lee

Abstract

We report a facile metal transfer method to create metal patterns on polydimethylsiloxane (PDMS) surface. The metals were first patterned on polyethylene terephthalate (PET) substrate, and then transferred to PDMS simply by oxygen plasma treatment. The transfer was enabled by weakened metal-PET adhesion due to undercut and charge repulsion. In this way, we got rid of adhesion layers and sacrificial layers that were required by conventional methods. Ours is a fast and convenient method as it takes place at room temperature with just a gentle contact of PET and PDMS. The resolution of this method was found to be in sub-micron range and the morphologies of different transferred patterns were characterized. With such a method, we successfully fabricated some unconventional metamaterial devices, including a double-sided broadband THz filter with a stop band bandwidth of 1.4 THz, and devices on paper, fabric, leaf and nonplanar surfaces. 

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

Full Article: http://www.opticsinfobase.org/view_article.cfm?gotourl=http%3A%2F%2Fwww%2Eopticsinfobase%2Eorg%2FDirectPDFAccess%2F8A138ABB-D945-AB4D-C6B721979EDDA8C1_312758%2Fome-5-4-733%2Epdf%3Fda%3D1%26id%3D312758%26seq%3D0%26mobile%3Dno&org=

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

Abstract

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.

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

Full Article: en/Content/ArticleLanding/2015/CP/C5CP01195G?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FCP+%28RSC+-+Phys.+Chem.+Chem.+Phys.+latest+articles%29#!divAbstract

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

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.


Abstract

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.

This study was performed using TeraView's Spectra 1000 system. (TeraView, Cambridge, UK)

Full Article: http://ieeexplore.ieee.org/xpl/abstractAuthors.jsp?arnumber=6930809&contentType=Journals+%26+Magazines

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

USE of COC substrates for millimeter-wave devices

Iñigo Ederra and Ramon Gonzalo


Abstract

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

Full Article: http://onlinelibrary.wiley.com/doi/10.1002/mop.28848/abstract

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

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


Abstract

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.

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

Full Article: http://ieeexplore.ieee.org/xpl/abstractAuthors.jsp?tp=&arnumber=6920006&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6920006