Attosecond pulse characterization by XUV nonlinear optics

Abstract

We demonstrate the generation of intense isolated pulses from a Single harmonic (photon energy 27.9 eV) by using sub-10-fs blue laser pulses. Nonadiabatic evolution of the blue laser pulse produces a large dipole moment at the relatively low (ninth) harmonic order and the ionization of neutral gas interacting with the laser electric field shortens the harmonic pulse duration, resulting in the high-peak intensity at focus. A nonlinear optical process in the extreme ultraviolet (XUV), i.e., two-photon above-threshold ionization, was successfully observed. XUV pulses with a temporal duration of 950 as were characterized by the autocorrelation technique and were found to be close to Fourier transform limit, supported by a numerical Simulation of the single-atom response to a laser electronic field. © 2007 Springer-Verlag New York.