Single-beam coherent anti-Stokes Raman scattering (CARS) spectroscopy of gas-phase CO2 via phase and polarization shaping of a broadband continuum



Coherent anti-Stokes Raman scattering (CARS) spectroscopy of gas-phase CO2 is demonstrated using a single femtosecond (fs) laser beam. A shaped ultrashort laser pulse with a transform-limited temporal width of ∼7 fs and spectral bandwidth of ∼225 nm (∼3500 cm−1) is employed for simultaneous excitation of the CO2 Fermi dyads at ∼1285 and ∼1388 cm−1. CARS signal intensities for the two Raman transitions and their ratio as a function of pressure are presented. The signal-to-noise ratio of the single beam–generated CO2 CARS signal is sufficient to perform concentration measurements at a rate of 1 kHz. The implications of these experiments for measuring CO2 concentrations and rapid pressure fluctuations in hypersonic and detonation-based chemically reacting flows are also discussed. Copyright © 2010 John Wiley & Sons, Ltd.