PHASE-CONJUGATE RESONANT HOLOGRAPHIC-INTERFEROMETRY APPLIED TO NH CONCENTRATION MEASUREMENTS IN A 2-DIMENSIONAL DIFFUSION FLAME

Resonant holographic interferometry is a diagnostic technique based on the dispersion of light having a frequency close to that of an electr onic transition of a molecule. We propose a novel single-laser, two-co lor setup for the recording of resonant holograms and apply it to two- dimensional (2D) species concentration measurements in a combustion en vironment. The generation of the second color is achieved by optical p hase conjugation from stimulated Brillouin scattering in a cell. The f requency shift of similar to 8.5 GHz introduced by the phase conjugati on matches approximately the linewidth of many molecular transitions a t typical flame temperatures and can be implemented to produce hologra ms of good contrast and diffraction efficiency. Phase-conjugate resona nt holographic interferometry is demonstrated in a 2D NH3-O-2 flame, y ielding interferograms containing information on the NH radical concen tration distribution in the flame. Experimental results are quantified by application of a numerical computation of the complex refractive i ndex. (C) 1997 Optical Society of America.