Plateau high harmonics are shown to be chirped. The experimental values of the chirp, in good agreement with purely classical kinematics or strong field approximation quantum theory are positive and inversely proportional to intensity. The various steps for the optimization of the attosecond pulse train are discussed.

Laser Phys.

Mairesse, Y., de Bohan, A., Frasinski, L. J., Merdji, H., Ciubotariu-Dinu, L., Monchicourt, P., … Salières, P. (2005). High-harmonics chirp and optimization of attosecond pulse trains. Laser Phys., 15, 863–870.