Absorption-sensitive diffuse reflection imaging of concealed powders using a terahertz quantum cascade laser.

School of Electronic and Electrical Engineering, University of Leeds, Leeds, LS2 9JT, UK.
Optics Express (Impact Factor: 3.55). 05/2008; 16(9):5997-6007. DOI:10.1364/OE.16.005997
Source: PubMed

ABSTRACT We report diffuse reflection imaging in air of concealed powdered samples using a terahertz quantum cascade laser. The sensitivity of the detection scheme to sub-surface absorption within samples is confirmed using fully-characterized powdered admixtures of polystyrene and polymethyl methacrylate (PMMA). Measurements of the backscattering intensity from these samples are then used in conjunction with Kubelka-Munk scattering theory, as well as several models based on the quasi-crystalline approximation, to extract the absorption coefficient of PMMA. Our research demonstrates the feasibility of high-resolution frequency-domain terahertz imaging for the detection and identification of concealed powders in a reflection geometry.

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