THz Beam Shaping Based on Paper Diffractive Optics

Agnieszka Siemion ; Andrzej Siemion ; Jaroslaw Suszek ; Adam Kowalczyk ; Jaroslaw Bomba ; Artur Sobczyk ; Norbert Palka ; Przemysław Zagrajek ; Andrzej Kolodziejczyk ; Maciej Sypek

Abstract:

Fast and intensive development of terahertz (THz) technology requires designing dedicated optical elements. Here, we generated complicated THz field distribution thanks to simple binary diffractive optical elements (DOEs) made from paper. The paper fabricated structures are lightweight, inexpensive, feasible for fast-prototyping purposes and they have high transparency in the THz range. Structures were designed and simulated in nonparaxial approach which suppresses the influence of geometrical aberrations and enables large apertures in comparison with their focal lengths. Such DOEs can be used in THz tomography, scanners, radiation sources collimation, focusing and gathering the radiation on the detector.

Full article available here.

Analysis of Wire-Grid Polarisers in Terahertz Spectral Range

Mičica ; Martin ; Bucko ; Václav ; Postava ; Kamil ; Vanwolleghem ; Mathias ; Lampin ; Jean-François ; Pištora ; Jaromír

Abstract:

Polarisers are important components in many optical applications working with polarised radiation, therefore it is need to know their behaviour at specified spectral range. Interest in terahertz (THz) radiation and its application in science, where we need polarisers was our motivation for study of commonly used polarisers this spectral range. In our paper we present THz measurement of free standing wire-grid (5 μm tungsten wire, 12.5 μm period) and polyethylene foil wire-grid (0.5 μm metallic stripes, 1.2 μm period) polariser.

Measurements were performed by terahertz time domain spectroscopy in the range from 60 GHz to 3 THz (2–100 cm−1) at different rotation of azimuth angle. For quality evaluation was from measured data calculated extinction ratio and phase shift. Both polarisers were compared and their suitability for THz application is discussed. Results show better properties of free standing wire-grid polariser in the range up to 60 cm−1 while properties of polyethylene polariser are better at higher wavenumbers. Polarisers are described in the frame of Jones matrix calculus.

Full article available here.

Studying the Kinetics of n-Butyl-Cyanoacrylate Tissue Adhesive and Its Oily Mixtures

Marie Nedvedova ; Vojtech Kresalek, ; Hana Vaskova ; Ivo Provaznik

Abstract:

This study deals with the measurement of the kinetics of tissue adhesives used for supporting the hemostasis and wound closure during surgical intervention. There are available several types of adhesives of different composition which is closely related with their application. When selecting an appropriate adhesive, the time of curing could play an important role because some applications may require very fast polymerization for prompt vessel or wound closure; conversely, some situations need slower solidification because of longer manipulation with the glue during surgery.

The terahertz time-domain spectroscopy is used for studying the kinetics of the n-butyl-cyanoacrylate glue in this study. An oily substance is added to the glue samples to slow the reaction rate. The technique of attenuated total reflection is used in this application; the defined amount of glue sample or its mixture is applied on the silicon crystal and the terahertz response is measured in time. This time dependences are analyzed to find time constants for mathematical description of the glue kinetics. Further, the investigated samples were analyzed using light microscopy and Raman spectroscopy for description of the structures and compositions.

Full article here.

Terahertz Imaging Platform to Characterize the Growth of In-Vitro Breast Tumors

Abstract:

This study aimed at evaluating the ideal plating method and density for imaging with the terahertz (THz) spectrometer. In this study, different methods were used to grow in-vitro tumors using the 4T1 cell line. Here, attempts to grow breast tumors in-vitro were conducted. Results were produced in two environments, flat-bottomed plates and round-bottomed multiwell plates. The second method allowed for faster clumping and increased cell aggregation, producing tumors up to 7mm. Terahertz spectroscopy produced images that correlated well to photomicrographs taken of the in-vitro tumors. This methodology shows great promise for providing a reliable, parameter-controlled source of in-vitro breast tumors for research needs on breast tumor margins. 

Link to PDF

Microwave shielding and DC Electrical Properties of Carbon Black Loaded Rubber Nano-Composites

Abstract

In this work, ten carbon black (CB) loaded elastic acrylonitrile butadiene rubber (NBR) nano-composites have been prepared to be used in microwave shielding applications. The DC electric properties of these CB loaded NBR composites have been studied. The evolution of DC conductivity of CB loaded NBR composites with loading level revealed S-shapes curve in accordance with the percolation theory. The current (I)-voltage (V) relations have been studied for these samples at room temperature. All CB loaded NBR composite samples showed Ohmic behavior with the exception of two samples namely CB30 and CB40 in which space charge limited conduction is obvious. Microwave shielding has been calculated from the transmittance data measured using terahertz time domain spectroscopy (THz-TDS) technique. The analysis of microwave shielding data revealed that the sample CB70 has the highest shielding effectiveness. The results of the microwave shielding effectiveness of CB loaded NBR composites were correlated to their DC electric conductivities. Results showed that there is a strong relationship between the DC electric conductivity of the samples and their activity regarding microwave shielding effectiveness. The current investigation of microwave shielding properties of CB loaded NBR composites magnifies the importance of DC electric conduction losses as a major mechanism for microwave shielding.

http://www.jmest.org/wp-content/uploads/JMESTN42350842.pdf

TPS Spectra 3000, (TeraView, UK) was used for measuring transmittance of the samples in the frequency range 10-1000 GHz

THz structures fabricated in laser direct patterning

Koziol, P.E. ; Antonczak, A.J. ; Walczakowski, M. ; Palka, N. 










Abstract

In this paper two different methods of the manufacture of metamaterial structures using a laser treatment were presented. One of them is related to direct metallization of the surface of aluminum nitride ceramics (AlN) by interaction of laser radiation. The second method involves a process of selective removal of the conductive layer (silver) in the laser ablation process. It has been proved that both proposed methods allow to produce a structure of SRR type showing its properties in THz range. Obtained results allow to implement these methods for the manufacture of more complex structures. An advantage of the process of laser radiation interaction on the surface of a material is the ability to produce any shape without having to adapt further process components.

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

Full Article: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?tp=&arnumber=6948562&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6948562

Flat THz leaky wave antennas: Analysis and experimental results

Beaskoetxea, Unai ; Beruete, Miguel ; Zehar, Mokhtar ; Agrawal, Amit 

Abstract

Here, two different THz radiating structures are analyzed, consisting both of a central slot surrounded by annular or straight corrugations. Concentrically grooved antenna presents a moderately high gain. Its radiation and temporal properties are analyzed both numerically and experimentally. For the second case, no appreciable differences in terms of radiation characteristics are observed when the grooves' profile is changed from square to triangular. Manufactured triangular grooves antenna shows good performance for the experimental measurements at 0.5THz. These results could be of interest for the development of new THz sources and detectors.

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

Full Article: http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6948592&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6948592

Wavelet denoising and reconstruction of a microneedle embedded in human skin ex-vivo using terahertz pulsed reflectance

Mueller-Holtz, Martin ; Smith, Geoff

Abstract

Biological tissue can show promising features in the terahertz region of the electro-magnetic spectrum but face the problem that the signal to noise ratio can be poor due to the low energy output from the measurement instrument coupled with the high absorbance of water in biological tissue. Wavelet denoising and reconstruction are known to be suitable digital signal processing filters for reflected terahertz energy when appropriate thresholds, scales and mother-wavelets are chosen. In this article, we therefore describe a Wavelet transform-based method for denoising reflections of THz energy from ex-vivo human skin with an embedded microneedle. The wavelet reconstruction was then successfully used to identify the microneedle from the reflected waveform. This technique is potentially useful to enhance in-depth analysis and visualisation of underlying skin layers, lesions and penetration depth for targeted drug delivery.

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

Full Article: http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6945175&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6945175

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)

Terahertz and Raman spectra of non-centrosymmetrical organic molecular crystals

Monika Trzebiatowska-Gusowska, Edward F. Plinski, Jan Baran, Michal J. Walczakowski, Przemyslaw P. Jarzab, Kacper Nowak, Boguslaw Fuglewicz, Martin Mikulics, Norbert Palka, Mieczyslaw Szustakowski

Abstract

The terahertz waves have been applied to the spectroscopy of molecular crystals. The group based on hybrid organic–inorganic crystals like triglycine zinc chloride, triglycine sulphate, triglycine selenate, diglycine hydrobromide, diglycine hydrochloride, diglycine lithium nitrate, glycine lithium nitrate has been considered. The dispersion relation phonon–polariton have been shown between 10 cm−1 and 80 cm−1 for diglycine lithium nitrate, triglycine zinc chloride, and diglycine hydrobromide.

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

Full Article: http://www.sciencedirect.com/science/article/pii/S0925346714001992

Photoinduced active terahertz metamaterials with nanostructured vanadium dioxide film deposited by sol-gel method

Yaxin Zhang, Shen Qiao, Linlin Sun, Qi Wu Shi, Wanxia Huang, Ling Li, and Ziqiang Yang 

Abstract

Applying the photoexcitation characteristics of vanadium dioxide (VO₂), a dynamic resonant terahertz (THz) functional device with the combination of VO₂ film and dual-resonance metamaterial was suggested to realize the ultrafast external spatial THz wave active manipulation. The designed metamaterial realizes a pass band at 0.28–0.36 THz between the dual-resonant frequencies, and the VO₂ film is applied to control the transmittance of the spatial THz wave. More than an 80% modulation depth has been observed in the statics experiment, and the dynamic experimental results illustrate that this active metamaterial realizes up to a 1 MHz amplitude modulation signal loaded on a 0.34 THz carrier wave without any low noise amplified devices. The electromagnetic properties and photoinduced dynamic characteristics of this structure may have many potential applications in THz functional components, including modulators, intelligent switches, and sensors.

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

Full Article: http://www.opticsinfobase.org/oe/fulltext.cfm?uri=oe-22-9-11070&id=284315

A pseudo-planar metasurface for a polarization rotator

W. Zhang, W. M. Zhu, E. E. M. Chia, Z. X. Shen, H. Cai, Y. D. Gu, W. Ser, and A. Q. Liu 

Abstract

New demonstrations of effective interaction between light and artificially electromagnetic interface, or the metasurface, have stimulated intensive research interests on control of light to realize applications in beam steering, optical imaging and light focusing, etc. Here we reported a new type of planar metasurface of which every individual metamolecule is single metallic layer with stereo structure and the metasurface is name as Pseudo-Planar Metasurface (PPM). The metamolecule of the PPM is a chiral structure and therefore derives significant optical activity.

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

Full Article: http://www.opticsinfobase.org/oe/fulltext.cfm?uri=oe-22-9-10446&id=284135

Spoof Plasmon Surfaces A Novel Platform for THz Sensing

Binghao Ng , Jianfeng Wu , Stephen M. Hanham , Antonio I. Fernández-Domínguez ,
Norbert Klein , Yun Fook Liew , Mark B. H. Breese , Minghui Hong , and Stefan A. Maier*




Spoof plasmon surfaces consisting of linear arrays of subwavelength grooves are proposed as a novel platform for THz sensing. The tightly confined spoof plasmons, coupled via an Otto prism setup, are sensitive to the refractive index of the dielectric filling the grooves. Phase jumps at spoof plasmon resonances are used as a readout response for refractive index sensing. An overall sensitivity of 0.49 THz RIU⁻¹ with figures-of-merit as high as 49 are achieved.

Measurements performed using TeraView's TPS Spectra 3000 system. (TeraView, Cambridge, UK)

Full Article: http://onlinelibrary.wiley.com/doi/10.1002/adom.201300146/abstract?deniedAccessCustomisedMessage=&userIsAuthenticated=false

Identification of concealed materials, including explosives, by terahertz reflection spectroscopy

Norbert Palka

Military University of Technology

Abstract

We report on a method for extracting the characteristic features of covered materials, including hexogen, in the range from 0.5 to 1.8 THz. This time-domain spectroscopy-based technique takes into account only part of the signal reflected from a covered sample and analyzes it by using the Fourier transform. The obtained power spectrum has distinctive peaks that correspond to peaks measured in the transmission configuration and can be used for further identification of the materials.

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

Full Article: http://opticalengineering.spiedigitallibrary.org/article.aspx?articleid=1787555

Effect of growth temperature on the terahertz-frequency conductivity of the epitaxial transparent conducting spinel NiCo2O4 films

Punam Silwal¹, Chan La-o-vorakiat², Elbert E. M. Chia², Dae Ho Kim³, and Diyar Talbayev¹

¹Department of Physics and Engineering Physics, Tulane University, 6400 Freret Street, New Orleans, LA 70118, USA
²Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
³Corporate R&D institute, Samsung Electro-Mechanics, 150 Maeyeong-ro, Suwon, Gyunggido 443-743, Korea 

Abstract

We have measured the terahertz-frequency optical conductivity of the epitaxial inverse spinel NiCo₂O₄ films grown at different temperatures. The low-temperature-grown film exhibits a metallic behavior with ferrimagnetic ordering, while the high-temperature-grown film shows greatly suppressed magnetization and insulating behavior. Both films exhibit band-like coherent conduction at intermediate temperatures, albeit with very different carrier densities consistent with the proposed models of cation valencies in this mixed-valence material. Both films also display a crossover to incoherent transport at low temperatures, indicating a disorder-induced tendency toward localization.

The real (ε₁) and imaginary (ε₂) parts of the measured dielectric function of the NCO300 film. 

Two different spectrometers were used for this study: a home-built spectrometer THz-TDS, and a commercial spectrometer mede by Teraview. TeraView's TPS Spectra 3000 was used to perform measurements. 

Extension of the p-Spectrum Method to the Higher Frequencies

N. Palka
Institute of Optoelectronics, Military University of Technology, S. Kaliskiego 2, 00-908 Warsaw, Poland

Abstact
The p-spectrum method is a time domain spectroscopy-based technique for re flection analysis of materials (including explosives) that takes into account only part of the re flected signal, which is next analyzed via the Fourier transform. The method is limited to the frequencies of about 1.8 THz due to the pulse properties of our time domain spectroscopy setup. In this paper we theoretically prove that application of a shorter pulse can increase this frequency range up to 2.2 THz, that enables analysis of penthrite and octogen, two important explosives.

ACTA PHYSICA POLONICA A Vol. 124(3) 543 (2013)

..........The proposed TDS-based p-spectrum method uses an external free standing module with a fiber-fed emitter and detector (Fig. 1a). This module is connected to the core unit of the Spectra 3000 from Teraview Company by means of optical fibers. The THz beam thanks to a set of the o -axis parabolic and at mirrors is focused on the sample and after specular re flection is collected and focused on the detector.   ..............

see full paper at http://przyrbwn.icm.edu.pl/APP/PDF/124/a124z3p40.pdf

Characterization of T-ray Penetration to Composite Materials

Kwang-Hee Im, David K. Hsu, Chien-Ping Chiou, Daniel J. Barnard and In-Young Yang

Department of Auto. Eng., Woosuk University 490, Samrae-up, Wanju-kun, Chonbuk, 565-701, Korea

Center for Nondestructive Evaluation, Iowa State University, Ames, Iowa 50011, USA

School of Mechanical Eng., Chosun University, 375 Seosuk-dong, Dong-gu, Kwangju 501-759, Korea

Abstract

Using T-ray (Terahertz waves) characterization of the non-destructive evaluation was made on the penetration on composite materials. The modalities of the T-ray radiation used were time domain spectroscopy (TDS) and continuous wave (CW) for composites. The composite materials investigated include both non-conducting polymeric composites and carbon fiber composites. T-ray signals in the TDS mode resembles that of ultrasound; however, unlike ultrasound, T-ray pulse can detect a crack hidden behind a larger crack (shadow effect). Thick GFRP laminates containing double saw cuts was tested. Also, in carbon composites the penetration of T-ray waves was investigated in order to detect flawsis strongly affected by the angle between the electric field vector of the terahertz waves and the intervening fiber directions. The T-ray effect was intensively studied between the carbon fiber direction and the electric field of T-ray. Other composites tested in this study include both solid laminates and honeycomb sandwiches. The defects and anomalies investigated by T-ray were foreign material inclusions, simulated disbond and delamination, mechanical impact damage, and water or hydraulic fluid ingression. The intensive characterization of T-ray for the NDE of composites is being discussed.

... 2. T-ray system 2.1 T-ray scanner The terahertz instrumentation systems used in this research
were provided by TeraView Limited. The instrumentation includes a time domain spectroscopy
(TDS) pulsed system and a frequency domain continuous wave (CW) system. ...

Keywords: T-ray, Time domain spectroscopy, Composite materials, Penetration.

Full paper

Hybrid SRRs Design and Fabrication for Broadband Terahertz Metamaterials

Pan, Z.Y. Zhang, P. ; Chen, Z.C. ; Vienne, G. ; Hong, M.H.

IEEE Photonics Journal 4(5), 1267 – 1272, (2012)

Data Storage Inst., Agency for Sci., Technol. & Res. (A*STAR), Singapore, Singapore

ABSTRACT

Hybrid metamaterials comprising split-ring resonator (SRR) structures with different gap dimensions are fabricated on polyethylene naphthalate (PEN) films by parallel laser micro-lens array (MLA) lithography and a liftoff process. The unit cell of hybrid metamaterials consists of four SRRs with the same SRR core side length but different gap sizes. The different-gap-size SRRs in each unit cell correspond to different but successive resonance dips, which are coupled to form a significantly broader band with enhanced resonance. The hybrid SRRs design is numerically and experimentally demonstrated, showing a much broader bandwidth to cover all narrowband induced by each SRR and enhanced resonance as compared with a uniform SRR design.

......The pitch p of the samples is defined by the pitch size of the MLA, which is fixed at 100 m. The sample characterization is carried out with a THz time-domain spectroscopy (THz-TDS) system (TPS3000, Teraview Inc.) in ..


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Surface relief structures for a flexible broadband terahertz absorber

Dong-Hyun Kim,1 Dae-Seon Kim,1 Sehyun Hwang,2 and Jae-Hyung Jang1,2,3,*

1School of Information and Communications, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712, South Korea

2Research Institute for Solar and Sustainable Energies, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712, South Korea

3Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712, South Korea

Abstract

Terahertz (THz) absorbers with surface relief structures (SRSs) were designed and fabricated on a flexible polydimethylsiloxane(PDMS) substrate by using a stamping method. The silicon mold used for the stamping process was prepared by using a crystallographic wet etching method with 45% KOH solution at 80°C. The flexible THz absorber, consisting of micropyramids with a base width of 240 μm, demonstrated nearly perfect absorbance higher than 99% owing to the dramatically reduced surface reflectance of the SRS. The reflectance of the PDMS with the SRS was less than 1%, which is only 1/100th of that measured from a bare PDMS at frequency higher than 1 THz.

... of 240 μm. The reflectance and transmittance of the fabricated flexible PDMS-based SRS samples were measured with a terahertz time-domain spectroscopy (THz-TDS) system (TPS spectra 3000, TeraView). The THz-TDS ...

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