The above photo shows simultaneous particle image velocimetry (PIV) and planar laser-induced fluorescence of the OH radical (OH PLIF) measurements in progress. Two Nd:YAG lasers (green light), with pulses approximately 10 microseconds apart, are combined before being formed into a sheet and passed through the flame.
Part of a Nd:YAG beam is extracted and used to pump a dye laser (right). The tunable light from the dye laser is sent through a frequency-doubler to create the UV light (fluoresced as blue) required for OH PLIF. The UV beam is then recombined with the Nd:Yag beams and sent through the flame.
An intensified camera (center right) is used to image the UV fluorescence from OH, while a 2K x 2K CCD (center left) collects light scattered from seeded particles in the flame for the PIV measurement.