The generation of attosecond pulses by superposition of high harmonics relies on their synchronization in the emission. Our experiments in the low-order, plateau, and cutoff regions of the spectrum reveal different regimes in the electron dynamics determining the synchronization quality. The shortest pulses are obtained by combining a spectral filtering of harmonics from the end of the plateau and the cutoff, and a far-field spatial filtering that selects a single electron quantum path contribution to the emission. This method applies to isolated pulses as well as pulse trains.
Phys. Rev. Lett.

Mairesse, Y., de Bohan, A., Frasinski, L. J., Merdji, H., Ciubotariu-Dinu, L., Monchicourt, P., … Salières, P. (2004). Optimization of attosecond pulse generation. Phys.Rev.Lett., 93(Article number: 163901), 1–4. doi:10.1103/physrevlett.93.163901