Backscattered coherent anti-Stokes Raman scattering for at range detection of dipicolinic acid and four-wave mixing multiple scattering

Author： Huang Yu Soroka Andrew Cohen Kenneth Dogariu Arthur

Publisher： Taylor & Francis Ltd

ISSN： 1362-3044

Source： Journal of Modern Optics, Vol.54, Iss.16-17, 2007-11, pp. : 2473-2480

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

We investigate femtosecond coherent anti-Stokes Raman scattering (CARS) signals collected at range from dipicolinic acid (DPA), one of the marker molecules within anthrax spores. The backscattered CARS signal from the DPA solution recorded versus probe pulse delay exhibits molecular coherence beating. We show a signal-to-noise ratio better than two orders of magnitude for a sample placed 12 m away, and infer the possibility of detection at range over distances of hundreds of metres. We also study the backscattered CARS signals from DPA powder. The beat signal exhibits two vibrational modes with a level spacing of 70±10 cm- 1, which matches very well with the literature value of 69 cm- 1. We quantitatively study the effects of multiple scattering in four-wave mixing from powder samples and estimate an 8 µm mean distance between the scattering events.