Contrast optimization of two-photon processes after a microstructured hollow-core fiber demonstrated for dye molecules

Abstract

We demonstrate selective excitation of dyes with overlapping absorption spectra in solution with pulses transmitted through a hollow-core fiber. Thereto we show how dispersive effects occurring in the fiber can be compensated and what the limiting pulse energies are. Furthermore, an overview over various phase parametrizations is given and we examine which are best used when optimizing a two-photon fluorescence contrast of two dyes in a sample. This could be relevant for future endoscopic applications as well as state of the art two-photon microscopy.

Influence of nonlinear effects on the three-photon excitation of L-Tryptophan in water using phase-shaped pulses

“…Especially when strong fluorescence is required for spectroscopy, three-photon excitation is inherently coupled to spectral changes of the exciting laser spectrum in the sample. As shown in earlier publications [23,24], one can achieve selective excitation of fluorophores by pulse shaping. This method could be applied as well to nonresonant threephoton processes.…”

Combined temporal and spatial laser pulse shaping for two-photon excited fluorescence contrast improvement

“…The antisymmetric third order phase has the advantage to yield a sharp maximum of the two-photon field [12]. By shifting the position of the antisymmetric function on the temporal shaper the turning point of the function and hence the sharp maximum is shifted to different wavelengths [24]. This enables to scan the spectrum of the Ti:Sa laser with the antisymmetric phase function for the individual dyes.…”