PHOTON-COUNTING TECHNIQUE FOR RAPID FLUORESCENCE-DECAY MEASUREMENT

We report on a novel laser-induced fluorescence triple-integration met hod (LIFTIME) that is capable of making rapid, continuous fluorescence lifetime measurements by a unique photon-counting technique. The LIFT IME has been convolved with picosecond time-resolved laser-induced flu orescence, which employs a high repetition-rate mode-locked laser, per mitting the eventual monitoring of instantaneous species concentration s in turbulent flames. We verify the technique by application of the L IFTIME: to two known fluorescence media, diphenyloxazole (PPO) and qui nine sulfate monohydrate (QSM). PPO has a fluorescence lifetime of 1.2 8 ns, whereas QSM has a fluorescence lifetime that can be varied from 1.0 to 3.0 ns. From these liquid samples we demonstrate that fluoresce nce lifetime can currently be monitored at a sampling rate of up to 50 0 Hz with less than 10% uncertainty (la). (C) 1998 Optical Society of America.