Coherent control for species selectivity in a flat-flame using femtosecond/picosecond coherent Raman scattering

Abstract

Coherent control for the selective spectral suppression of combustion species using femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) is presented. Phase modulation of one of the excitation pulses was accomplished using a 4-f pulse shaper with a spatial light modulator at the Fourier plane. A feedback-controlled genetic algorithm was used to search for the appropriate modulated waveform in a non-reacting gas jet of known composition; the selected phase function was subsequently applied in a H${}_2$/air flat-flame diluted with CO${}_2$. Q-branch transitions of O${}_2$ and CO${}_2$ were targeted. To our knowledge, this is the first demonstration of coherent control using fs/ps CARS for spectral species selectivity in a combustion environment.