Use of a synchronously pumped picosecond laser for excitation of a spectrofluorimetric single-photon counting system

A nanosecond spectrofluorimeter for the counting of single photons emitted by a sample excited by laser pulses of 1.6–3.7 psec duration was used to determine the instrumental function of a PRA 3000 nanosecond spectrofluorimeter (half-width 0.62 ± 0.04 nsec at λ =590–615 nm) and to investigate the operation of a picosecond laser with an acoustooptic deflector. It was found that the radiation emitted by a synchronously pumped dye laser with a pulse repetition frequency controlled by an acoustooptic deflector included not only the pulses of the expected frequency but also stray pulses at the pump frequency. Careful synchronization of the acoustooptic deflector pulses with the pump pulses made it possible to reduce the relative amplitude of the stray pulses from 30% to 0.3%.