Two-color (two-photon) excitation fluorescence with two confocal beams and a Raman shifter

摘要

Two-color (two-photon) excitation fluorescence (2CF) with two confocal excitation beams is demonstrated with a Raman shifter as excitation light source. Coumarin 6H dye sample (peak absorption approximate to 394 nm, peak fluorescence 490 nm) is excited using the first two Stokes outputs (683, 954 nm, two-color excitation = 398 nm) of a Raman shifter pumped by a 6.5 ns-pulsed 532 nm-Nd:YAG laser (repetition rate = 10 Hz). The two Stokes pulses overlap for about 6 ns and two-color fluorescence is generated even with focusing objectives of low numerical apertures (NA < 0.4). We observed the linear dependence of the two-color fluorescence signal with the product of the average intensities of the two Stokes excitation beams. The two-color fluorescence distribution is strongly localized around the common focus of the confocal excitation beams. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 15]