A new frequency-domain fluorometer is described which is capable of operating over a frequency range between 10 MHz and 1 GHz. The instrument employs a mode-locked Ar-ion laser as an 82-MHz repetitionrate excitation source and an inexpensive extracavity acoustooptic light modulator for secondary-frequency generation. The instrument is very rapid and can acquire, in ~10 s, the entire frequency spectrum necessary to determine excited-state lifetimes. Importantly, these frequency spectra are characterized by signal-tonoise ratios of at least 20 for moderate fluorescence signals (10–20 µA detector current). With this new instrument, multiple exponential decays can be easily resolved, and single exponential decays can be determined at a precision (standard deviation) of better than 20 ps.
© 1987 Optical Society of America
Frank V. Bright and Gary M. Hieftje, "Rapid-scanning frequency-domain fluorometer with picosecond time resolution," Appl. Opt. 26, 3526-3529 (1987)