It is shown that the beat frequencies inherent to a mode-locked dye laser can be used in phase fluorometry. The fluorescence lifetime of cresyl violet, quenched by KI, is determined with the use of the first two harmonics of a synchronously pumped dye laser. The results from the two frequency components are in excellent agreement. The fluorescence lifetime is determined by time-resolved spectroscopy, with the use of the same sample and photomultiplier. The data show that narrower confidence intervals are obtained in the phase-resolved measurement, and this result is attributed to the high phase stability of a cw mode-locked laser.
