We demonstrate real-time stand-off detection and imaging of trace explosives using collinear, backscattered Coherent Anti-Stokes Raman Spectroscopy (CARS). Using a hybrid time-resolved broad-band CARS we identify nanograms of explosives on the millisecond time scale. The broad-band excitation in the near-mid-infrared region excites the vibrational modes in the fingerprint region, and the time-delayed probe beam ensures the reduction of any non-resonant contributions to the CARS signal. The strong coherent enhancement allows for recording Raman spectra in real-time. We demonstrate stand-off detection by acquiring, analyzing, and identifying vibrational fingerprints in real-time with very high sensitivity and selectivity. By extending the focused region from a 100-micron sized spot to a 5mm long line we can obtain the spectral information from an extended region of the remote target with high spatial resolution. We demonstrate fast hyperspectral imaging by one-dimensional scanning of the Line-CARS. The three-dimensional data structure contains the vibrational spectra of the target at each sampled location, which allows for chemical mapping of the remote target.

Date Published: 4 May 2012
PDF: 9 pages
Proc. SPIE 8358, Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XIII, 83580R (4 May 2012); doi: 10.1117/12.919568

Published in SPIE Proceedings Vol. 8358:
Chemical, Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing XIII
Augustus Way Fountain III, Editor(s)