ESTIMATION OF SPATIAL AVERAGING OF TEMPERATURES FROM COHERENT ANTI-STOKES-RAMAN SPECTROSCOPY

Spatial averaging is a potential problem in the application of coheren t anti-Stokes Raman spectroscopy (CARS) to combustion diagnostics when varying temperatures and composition are present at spatial scales sm aller than the typical 1-2-mm spatial resolution of CARS. The observed CARS spectrum is then a mixture of the hot and cold components. We sh ow that simulated, spatially averaged spectra, generated by the incohe rent addition of intensities, can be significantly different from thos e obtained by the coherent addition of the electric held amplitudes of the component spectra. The analyses of these simulated, spatially ave raged CARS spectra demonstrate that the use of theoretical CARS spectr a, generated by the addition of intensities of the hot and cold compon ents of a binary gas mixture, can lead to errors in the estimated flam e temperatures. (C) 1996 Optical Society of America