title: Standoff photoacoustic detection of explosives using quantum cascade laser and an ultrasensitive microphone.
abstract: Standoff detections of explosives using quantum cascade lasers (QCLs) and the photoacoustic (PA) technique were studied. In our experiment, a mid-infrared QCL with emission wavelength near 7.35 μm was used as a laser source. Direct standoff PA detection of trinitrotoluene (TNT) was achieved using an ultrasensitive microphone. The QCL output light was focused on explosive samples in powder form. PA signals were generated and detected directly by an ultrasensitive low-noise microphone with 1 in. diameter. A detection distance up to 8 in. was obtained using the microphone alone. With increasing detection distance, the measured PA signal not only decayed in amplitude but also presented phase delays, which clearly verified the source location. To further increase the detection distance, a parabolic sound reflector was used for effective sound collection. With the help of the sound reflector, standoff PA detection of TNT with distance of 8 ft was demonstrated.
authors.affiliation: Department of CSEE, University of Maryland, Baltimore County, Baltimore, Maryland 21250, USA. chxing1@umbc.edu
authors.forename: Xing
authors.initials: X
authors.lastname: Chen
authors.forename: Dingkai
authors.initials: D
authors.lastname: Guo
authors.forename: Fow-Sen
authors.initials: FS
authors.lastname: Choa
authors.forename: Chen-Chia
authors.initials: CC
authors.lastname: Wang
authors.forename: Sudhir
authors.initials: S
authors.lastname: Trivedi
authors.forename: A Peter
authors.initials: AP
authors.lastname: Snyder
authors.forename: Guoyun
authors.initials: G
authors.lastname: Ru
authors.forename: Jenyu
authors.initials: J
authors.lastname: Fan