Shaped pulses transported through an optical fiber in the nonlinear regime for selective excitation of two-photon transitions

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.