Potential for detection of explosive and biological hazards with electronic terahertz systems

Abstract

The terahertz (THz) regime (0.1-10 THz) is rich with emerging possibilities in sensing, imaging and communications, with unique applications to screening for weapons, explosives and biohazards, imaging of concealed objects, water content and skin. Here we present initial surveys to evaluate the possibility of sensing plastic explosives and bacterial spores using field-deployable electronic THz techniques based on short-pulse generation and coherent detection using nonlinear transmission lines and diode sampling bridges. We also review the barriers and approaches to achieving greater sensing-at-a-distance (stand-off) capabilities for THz sensing systems. We have made several reflection measurements of metallic and non-metallic targets in our laboratory, and have observed high contrast relative to reflection from skin. In particular, we have taken small quantities of energetic materials such as plastic explosives and a variety of Bacillus spores, and measured them in transmission and in reflection using a broadband pulsed electronic THz reflectometer. The pattern of reflection versus frequency gives rise to signatures that are remarkably specific to the composition of the target, even though the target's morphology and position is varied. Although more work needs to be done to reduce the effects of standing waves through time-gating or attenuators, the possibility of mapping out this contrast for imaging and detection is very attractive.

À la frontière onde-lumière

“…L'avantage de la THz-TDS est sa capacité à détec-ter ces produits même s'ils ont été délibérément dissimulés du fait de la bonne transmission du rayonnement THz à travers les dispositifs qui les contiennent [4]. Par ailleurs, des études sur la détection d'agents biologiques ont été publiées par Choi et al Les auteurs ont effectué des mesures de transmission sur l'enveloppe membranaire de B. cereus simulant l'action de B. anthracis [18]. Les signatures spectrales hautement spécifiques ont été enregistrées et prouvent que cette technique a un avenir certain pour la détection de ce type d'agression.…”

A Modified 8f Geometry with Reduced Optical Aberrations for Improved Time Domain Terahertz Spectroscopy

“…Among these techniques, time domain terahertz spectroscopy (TDTS) [1,2] has evolved into a ubiquitous tool within both the commercial and academic research landscape. Industrially, TDTS has been utilized in the fields of pharmaceuticals [3], medical imaging [4,5,6,7,8], protein detection [9], and biohazard applications [10,11]. TDTS has also made significant contributions to active fields of basic research such as materials characterization [12,13], superconductivity [14,15], quantum magnetism [16,17,18], and topological insulators [19,20,21].…”

Reduction of effective terahertz focal spot size by means of nested concentric parabolic reflectors

“…Time-domain terahertz spectroscopy (TDTS) 1 has seen tremendous growth is recent years and has found use in many different areas including security applications and biohazard detection, 2,3 detection of protein conformational changes, 4 structural and medical imaging, [5][6][7][8][9] monitoring of pharmaceutical ingredients, 10 and the characterization of materials. [11][12][13] In particular time-domain terahertz spectroscopy has been proven very useful in studying different material systems at low temperatures including superconductors, 14,15 quantum magnets, [16][17][18][19] exciton states in TiO 2 nanotubes, 20 and topological insulators.…”