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.