Quantitative differentiation of dyes with overlapping one-photon spectra by femtosecond pulse shaping.
We demonstrate that DiI and Rhodamine B, which are not easily distinguishable to one-photon measurements, can be differentiated and in fact quantified in mixture via tailored two-photon excitation pulses found by a genetic algorithm (GA). A nearly three-fold difference in the ratio of two-photon fluorescence of the two dyes is achieved, without a drop in signal of the favored fluorophore. Implementing an acousto-optic interferometer, we were able to prove that the mechanism of discrimination is second-harmonic tuning by the phase-shaped pulses to the relative maxima and minima of these cross-sections.
Tkaczyk
Eric R
ER
Center for Ultrafast Optical Science, University of Michigan, 2200 Bonisteel Blvd., Ann Arbor, MI 48109-2099, USA.
Tkaczyk
Alan H
AH
Mauring
Koit
K
Ye
Jing Yong
JY
Baker
James R
JR
Norris
Theodore B
TB