Monday, August 21, 2017

Abstract-A Robust Baseline and Reference Modification and Acquisition Algorithm for Accurate THz Imaging

 Xuequan Chen,  Edward P. J. Parrott ,  Benjamin S.-Y. Ung, Emma Pickwell-MacPherson

This paper reports an accurate baseline and reference modification and acquisition algorithm for terahertz (THz) reflection measurements. The algorithm solves the spatial phase variation problem, which is a major accuracy limitation of THz reflection imaging. It also overcomes the sampling error problem without taking multiple measurements by utilizing two-dimensional data fitting. The algorithm records the spatial information and the laser power status as a database to precisely modify the baseline and reference in a measurement, providing a simple, efficient, and accurate real-time baseline and reference acquisition method. The experimental results show that the algorithm significantly improves the accuracy of the extracted optical properties of the sample with only half of the time required in a traditional THz imaging by avoiding additional baseline and reference measurements. The strong robustness of the algorithm is also proved by the experiment, giving a stable performance against laser power fluctuations.

Abstract-Integrating THz Sensors/Structures Through Electrowetting in Dielectrics (EWOD) for Security Applications

L. Sirbu, L. Mihai, M. Danila, V. Schiopu, A. Matei, F. Comanescu, A. Baracu, A. Stefan, T. Dascalu, R. Muller

We developed a combination of technology for deposition contacts/wires upon nanoporous InP thin film structures and RF sputtering InP films. Indium phosphide (InP) films were deposited onto glass substrate using RF magnetron sputtering by varying the substrate temperature (50–100 °C), under constant argon pressure (6.3·10−3Bar) and RF power (100 W). To have good optimisation of growing parameters of LT-InP films we use several characterization techniques, Raman, FTIR, XRD, and THz spectroscopy, respectively. Doping with Ga ions was used to induce disordered in InP film, to reduce the optical recombination in IR spectra.

Abstract-Electromagnetic behavior of spatial terahertz wave modulators based on reconfigurable micromirror gratings in Littrow configuration

Jan Kappa, Klemens M. Schmitt, and Marco Rahm

Efficient, high speed spatial modulators with predictable performance are a key element in any coded aperture terahertz imaging system. For spectroscopy, the modulators must also provide a broad modulation frequency range. In this study, we numerically analyze the electromagnetic behavior of a dynamically reconfigurable spatial terahertz wave modulator based on a micromirror grating in Littrow configuration. We show that such a modulator can modulate terahertz radiation over a wide frequency range from 1.7 THz to beyond 3 THz at a modulation depth of more than 0.6. As a specific example, we numerically simulated coded aperture imaging of an object with binary transmissive properties and successfully reconstructed the image.

Sunday, August 20, 2017

Abstract-Terahertz Scattering and Spectroscopic Characteristics of Polymethacrylimide Microstructures

Liyun Xing , Hong-Liang Cui * , Jing Bai * , Zhenxiong Zhou * , Qingyu Zhou * , Dongshan Wei , Chunlei Du , Jun Yin , Songnian Zhang

We carried out systematic measurements of Polymethacrylimide (PMI)’s Terahertz (THz) spectroscopic and scattering parameters with various thicknesses and models. The Terahertz time domain spectroscopy (THz-TDS) would be useful as a nondestructive testing (NDT) tool for PMI. While the index of refraction is very close to that of air, with flat frequency dependency, the attenuation constant exhibits a remarkable strong frequency variation, suggesting a scattering dominated attenuation process. Based on the Mie scattering model, we gave the satisfactory explanation: the THz wave propagating through the PMI suffer scattering from the micro sized particles, and the sizes of the particles (shown to obey a normal distribution) determine the frequency characteristics of the interaction.

Abstract-Fabrication of Bi2212 Single Crystal Bolometer for Detection of Terahertz Waves

T. Semerci, Y. Demirhan, N. Miyakawa, H. B. Wang, L. Ozyuzer,

Terahertz (THz) radiation is in powerful region of electromagnetic spectrum because of prosperous application areas yet deficiency still exists about sources and detectors in despite of improvements of the research field in this range. This gap can be filled by focusing on development of THz detectors. Therefore, bolometers were preferred through many detectors due to detection sensitivity above 1 THz. In this study, Bi2Sr2CaCu2O8+δ (Bi2212) single crystals were used to fabricate THz bolometric detector. Bi2212 single crystals were transferred on sapphire substrate by cleavage process and e-beam lithography and ion beam etching were used to fabricate the microchip clean room facilities. Custom-designed cryogenic cryostat was used for a-b axis electrical and THz response measurements with liquid nitrogen cooled system. After electrical measurements, Bi2212 microchips detected the signals using Stefan-Boltzmann Lamp and response time were calculated. This study have shown with our experimental results that Bi2212 single crystals are potential candidates for THz bolometric detectors.