Document Type
Article
Publication Date
1-1-2005
Abstract
Backscattered signal of coherent anti-Stokes Raman spectroscopy can be an extremely useful tool for remote identification of airborne particles, provided the signal is sufficiently large. We formulate a semiclassical theory of nonlinear scattering to estimate the number of detectable photons from a bacterial spore at a distance. For the first time, the theory incorporates enhanced quantum coherence via femtosecond pulses and a nonlinear process into the classical scattering problem. Our result shows a large backscattered signal in the far field, using typical parameters of an anthrax spore with maximally prepared vibrational coherence. Using train pulses of 1 kHz of repetition rate each with energy of 10 mJ, we estimate that about 10(7) photons can be detected by a 1 m diameter detector placed 1 km away from the spore in the backward scattering direction. The result shows the feasibility of developing a real time remote detection of hazardous microparticles in the atmosphere, particularly biopathogenic spores.
Keywords
Nonlinear frequency-conversion, Dipicolinic acid, Light-pulses, Laser-pulses, Fast cars, Generation, Scattering, Spectroscopy, Propagation, Dynamics
Divisions
PHYSICS
Publication Title
Physical Review A
Volume
72
Issue
2
Additional Information
Department of Physics, Faculty of Science Building, University of Malaya, 50603 Kuala Lumpur, MALAYSIA