Femtosecond laser induced breakdown for combustion diagnostics

The focused beam of a 100 fs, 800 nm laser is used to induce a spark in some laminar premixed air-methane flames operating with variable fuel content (equivalence ratio). The analysis of the light escaping from the plasma revealed that the Balmer hydrogen lines, H-alpha and H-beta, and some molecular origin emissions were the most prominent spectral features, while the CN (B-2 Sigma(+)-X-2 Sigma(+)) band intensity was found to depend linearly with methane content, suggesting that femtosecond laser induced breakdown spectroscopy can be a useful tool for the in-situ determination and local mapping of fuel content in hydrocarbon-air combustible mixtures. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731781]