Probing attosecond pulse trains using "phase-control" techniques - art. no. 051801

We propose a method for the measurement of attosecond beating structures th at result from the superposition of harmonics of laser radiation. It utiliz es the phase control of the excitation probability of atoms through differe nt interfering channels. The channels consist of multiphoton excitation by the fundamental frequency and single-photon excitation by the superposition of the harmonic fields, or alternatively, by each harmonic or frequency in terval within the bandwidth of each harmonic. The method is sensitive to th e relative phase of the harmonics, including phases introduced by chirp. an d thus allows evaluation of the temporal structure of the superimposed harm onic fields. An experimental setup for the implementation of the method bas ed on freestanding transmission grating is suggested as well.