Abstract

The remote detection of gas phase molecules remains a challenge. Laser filamentation can be used to enhance the cross section for Raman scattering of gas phase molecules on the order of 10⁶–fold through impulsive excitation of vibrational modes of motion. The filament self shortens from 50 fs to <10 fs through the nonlinear processes of Kerr lensing, multiphoton ionization and self steepening. This pulse is short enough to coherently excite all Raman active modes of a medium including trace molecules in the gas phase. A probe pulse passing through the medium acquires measurable Raman sidebands from the macroscopic time-dependent polarization. The principals of the method will be presented along with applications to signature molecules.

© 2012 Optical Society of America