title: Use of photoacoustic excitation and laser vibrometry to remotely detect trace explosives.
abstract: In this paper, we examine a laser-based approach to remotely initiate, measure, and differentiate acoustic and vibrational emissions from trace quantities of explosive materials against their environment. Using a pulsed ultraviolet laser (266 nm), we induce a significant (>100  Pa) photoacoustic response from small quantities of military-grade explosives. The photoacoustic signal, with frequencies predominantly between 100 and 500 kHz, is detected remotely via a wideband laser Doppler vibrometer. This two-laser system can be used to rapidly detect and discriminate explosives from ordinary background materials, which have significantly weaker photoacoustic response. A 100  ng/cm2limit of detection is estimated. Photoablation is proposed as the dominant mechanism for the large photoacoustic signals generated by explosives.
authors.forename: C M
authors.initials: CM
authors.lastname: Wynn
authors.forename: R W
authors.initials: RW
authors.lastname: Haupt
authors.forename: J H
authors.initials: JH
authors.lastname: Doherty
authors.forename: R R
authors.initials: RR
authors.lastname: Kunz
authors.forename: W
authors.initials: W
authors.lastname: Bai
authors.forename: G
authors.initials: G
authors.lastname: Diebold