Permittivity and Loss Characterization of SU-8 Films for mmW and Terahertz Applications

Ghalichechian, N. ; Sertel, K.

Abstract

The dielectric permittivity measurement of thick SU-8 dielectric film is presented for entire frequency band of 1 GHz to 1 THz. SU-8 is a high-resolution UV-patternable photoresist that can be used for fabrication of high-aspect-ratio 3D structures for millimeter-wave and terahertz devices. Here, we report the measured dielectric constant and loss tangent of SU-8 films using terahertz time-domain spectroscopy. A quadratic polynomial model is established for the accurate calculation of complex permittivity up to 1 THz. The loss tangent of fully-cross-linked 430-μm-thick SU-8 film was measured to be 0.015, 0.027, and 0.055 at 1, 200, and 1000 GHz, respectively. Similarly, relative permittivity was found to be 3.24, 3.23, and 2.92. The fabrication process and level of cross-linking were demonstrated to have significant impact on the loss behavior of this material and the impact of cross liking on dielectric permittivity is quantified across a wide frequency band. The characterization results reported in this work is a platform for developing next-generation millimeter-wave and terahertz devices.

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

Full Article: http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6982221&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6982221

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Investigation of UV optical fibers under synchrotron irradiation

Dan Sporea, Laura Mihai, Adelina Sporea, Alin Lixandru, and Elke Bräuer-Krisch




Abstract

The focus of the present paper deals, for the first time, with commercial UV optical fibers, characterizing their behaviour as they are subjected to very high flux wiggler generated synchrotron radiation. Five distinct types of UV optical fibers, produced by three manufactures, were exposed to total doses between 5 Gy and 2000 Gy. The exposure to synchrotron radiation was performed in two campaigns. The tests were run off-line and considered the dependence of the radiation induced attenuation (RIA) as function of the total dose. The recovery of the radiation induced colour centres was studied at room temperature and after heating the samples up to 560 K. As a première, we also investigated through THz imaging and spectroscopy the irradiated optical fiber samples. Under these conditions, three of the optical fibers proved to be radiation resistant. The two optical fibers sensitive to synchrotron radiation exhibited a linear variation of the optical absorption at the wavelengths of λ = 229 nm, λ = 248 nm, and λ = 265 nm, for total doses between 60 Gy and 2000 Gy. These two samples showed also an increase of the optical absorption in the UV spectral range when heated to 560 K. The optical fibers sensitive to synchrotron radiation can potentially be used for on-line radiation dosimetry.

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

Full Article: http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-22-25-31473

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TeraView Limited is the world's leader in the design and manufacture of terahertz (THz) products to the pharmaceutical, security, medical and materials characterisation markets. Our products continue to yield many ground-breaking applications such as tablet coating thickness and uniformity, cracks, defect analysis, foreign materials and analysis of solid-state structure to be exploited by our customers. Based in Cambridge UK, we have a global client base and a highly-skilled workforce.

We are seeking a Software Development Specialist to join our team; an individual who is able to meet the existing operational needs of the company, as well as planning for the future needs of the company as we grow.

For a full job description and more information on the role, please visit: http://www.teraview.com/about/careers-jobs.html

Investigation of thermal degradation of vegetable oils by spectroscopic methods and its mathematical analysis

M. Tobolova, V. Kresalek, H. Vaskova and M. Buckova

Abstract

In this paper, relatively new spectroscopic methods were used for investigation of edible oils and their thermal degradation. There were included the samples of refined rapeseed and sunflower oil and the same oils heated for specified time interval at the temperature 200 °C. The optical characteristics of oils have been investigated with Terahertz Time Domain Spectroscopy (THz-TDS). The refractive indices were calculated in the specified terahertz frequency range, processed and statistically evaluated. The Wilcoxon matched pairs test was carried out for comparison of unheated and heated oil samples. The results measured by THz-TDS were supplemented by Raman spectra analysis. Both methods seem to be capable analyzing tool for oil investigation. 

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

Full Article: http://www.naun.org/main/NAUN/mcs/2014/a122002-078.pdf

Feasibility of Using Terahertz Spectroscopy To Detect Seven Different Pesticides in Wheat Flour

Maeng, Inhee; Baek, Seung Hyun; Kim, Hwa Yeon; Ok, Gyeong-Sik; Choi, Sung-Wook; Chun, Hyang Sook

Abstract

This study investigated the feasibility of detecting pesticides using terahertz (THz) spectroscopy in high-density polyethylene and/or wheat flour mixtures. The absorption spectra of seven pesticides (dicofol, chlorpyrifos, chlorpyrifos-methyl, daminozide, imidacloprid, diethyldithiocarbamate, and dimethyldithiocarbamate) were measured in the frequency range 0.1 to 3 THz at room temperature. Five of the seven pesticides exhibited specific absorption peaks in the low-energy THz range. The two remaining pesticides had no specific absorption peaks in this frequency range, but they exhibited different frequency-dependent refractive indices. The absorption coefficients of imidacloprid increased with its increasing weight ratio in high-density polyethylene, and the fitted power absorptions and refractive indices using a Maxwell-Garnett effective medium model were comparable to the measured data. Imidacloprid was also identified from its characteristic absorption peaks in wheat flour mixtures, and a linear relationship between the absorption coefficient and the weight ratio was observed. Our results show the potential of detection of selected pesticides in foods, such as wheat flour, using THz spectroscopy.

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

Full Article: http://www.ingentaconnect.com/content/iafp/jfp/2014/00000077/00000012/art00010