Abstract-Terahertz Differential Computed Tomography: a Relevant Nondestructive Inspection Application

Alexandre Duhant, Meriam Triki, Olivier Strauss

https://link.springer.com/article/10.1007/s10762-018-0564-5

In recent years, tremendous advances have been made in the choice of materials used in the industry. With weight reduction as the goal, composite and polymer materials are more and more popular but they are almost transparent to X-ray. Because of this, interest has grown in other wavelengths like terahertz (THz). Due to a difference in how X-ray and THz propagate, X-ray CT algorithms cannot be directly used. For example, THz induces refraction making the reconstruction problem nonlinear. In this paper, we present a new algorithm which complies with beam profile intensities, refraction, and reflection. It is based on linearizing the reconstruction process around a computer-aided design (CAD) model of the object to be reconstructed. The method we propose computes the deviation between the object and this model.

Abstract-InP double heterojunction bipolar transistors for terahertz computed tomography

AIP Advances

Dominique Coquillat, Alexandre Duhant, Meriam Triki, Virginie Nodjiadjim, Agnieszka Konczykowska, Muriel Riet, Nina Dyakonova, Olivier Strauss, Wojciech Knap

(a) Schematic of the InP DHBT THz detector and read-out circuit connections. (b) Input characteristics IBE − VBE of the 3-finger device. Inset: SEM photograph of a 3-finger DHBT with 3 × 10 μm × 0.7 μm emitter area. (c) Photo-voltage ΔU (left hand scale) and area normalized voltage responsivity RmeasV$R_V^{meas}$ (right hand scale) as a function of frequency for VBE = 0.43 V.

https://aip.scitation.org/doi/abs/10.1063/1.5039331

We present experimental studies of terahertz radiation detection by InP double heterojunction based transistors. We analyze the relation between their static characteristics and the experimentally determined voltage and current responsivities, showing importance of internal device parasitic capacitances and the external circuit loading effects. Finally, we demonstrate the use of these transistors for terahertz radiation computed tomography leading to 3D visualization of concealed objects. Our results pave the way towards wide use of heterojunction based transistors for terahertz imaging.