CO2 imaging with saturated planar laser-induced vibrational fluorescence

We present new vibrational (infrared) planar laser-induced fluorescence (PL IF) imaging techniques for CO2 that use a simple, inexpensive, high-pulse-e nergy transversely excited atmospheric CO2 laser to saturate a CO2 absorpti on transition at 10.6 mum. Strong excitation by use of a CO2 laser provides increased signal levels at flame temperatures and simplifies image interpr etation. Because rotational energy transfer and intramodal vibrational ener gy transfer are fast, vibrational distributions can be approximated by use of a simple three-temperature model. Imaging results from a 425 K unsteady transverse CO2 jet and a laminar coflowing CO/H-2 diffusion flame with temp eratures near 1500 K are presented. If needed, temperature-insensitive sign al levels can be generated with a two-laser technique. These results illust rate the potential for saturated infrared PLIF in a variety of flows. (C) 2 001 Optical Society of America.