We investigate the evolution of ultrashort pulses with an antisymmetric spectral phase during propagation through an optical fiber in presence of nonlinear effects. The shaped pulses are then applied for selective excitation of nonresonant two-photon transitions. Both numerical simulations and measurements confirm that a certain class of antisymmetric phase, a π-step, remains approximately antisymmetric-and is therefore suitable for the selective excitation-even though the pulse spectrum is significantly modified by self-phase modulation. Second-harmonic generation is used as a model two-photon transition. Furthermore, the capability of generating two perpendicularly polarized subpulses with independently shaped phase is demonstrated.

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Reverse propagation is a numeric technique that makes it possible to obtain arbitrarily shaped pulses after propagation through a fiber in the nonlinear regime. We apply it to achieve selective two-photon excitation of dyes that have overlapping absorption spectra with pulses transported through the fiber. By comparing both contrast and signal level it is shown that phase and amplitude shaped pulses generated using reverse propagation are superior to pulses with antisymmetric phase despite loss caused by amplitude shaping.