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

We show that nonlinear effects like self-phase modulation in a sample have to be considered for phase control of three-photon excitations. Furthermore, we demonstrate the control of three-photon excitation of L-Tryptophan in water using a pulse-shaping setup. Simulations of the propagation of the laser pulses in the cuvette exhibit good agreement with the experimental fluorescence scans at different laser intensities and show large discrepancies when neglecting nonlinear effects prior to the three-photon process. This can lead to improvements in selective excitation of amino acids by a near-infrared femtosecond laser source.