We present new vibrational (infrared) planar laser-induced fluorescence (PLIF) imaging techniques for CO<sub>2</sub> that use a simple, inexpensive, high-pulse-energy transversely excited atmospheric CO<sub>2</sub> laser to saturate a CO<sub>2</sub> absorption transition at 10.6 μm. Strong excitation by use of a CO<sub>2</sub> laser provides increased signal levels at flame temperatures and simplifies image interpretation. Because rotational energy transfer and intramodal vibrational energy transfer are fast, vibrational distributions can be approximated by use of a simple three-temperature model. Imaging results from a 425 K unsteady transverse CO<sub>2</sub> jet and a laminar coflowing CO/H<sub>2</sub> diffusion flame with temperatures near 1500 K are presented. If needed, temperature-insensitive signal levels can be generated with a two-laser technique. These results illustrate the potential for saturated infrared PLIF in a variety of flows.
© 2001 Optical Society of America
Brian J. Kirby and Ronald K. Hanson, "CO2 Imaging with Saturated Planar Laser-Induced Vibrational Fluorescence," Appl. Opt. 40, 6136-6144 (2001)