When interacting with a molecule or an atom, an intense ultra short laser
field periodically drives electron wave packets away and back to the parent
ion. At each return, the electron bunch may recombine to the initial
electronic state producing an XUV light burst of attosecond duration. The
characteristics of the XUV radiation is therefore directly mapped out from
the temporal and spectral structure of the electrons wave packets while
recolliding. Controlling the laser field to allow only one recollision
event is the key to produce a single attosecond pulse.
Here, for the first time, we have unambiguously achieved the temporal
confinement of XUV harmonic radiation down to an isolated attosecond burst
using the technique of polarization gating with (CEP) phase-stabilized
few-optical-cycle driving pulses [1]. The signature of a single attosecond
pulse emission has been observed in two gases, argon and neon, for three
different broad spectral ranges, 25-40 eV in argon and 35-70 eV or 50-100
eV in neon. While earlier work was limited to attosecond pulse bandwidth of
few eV hence to pulse longer than 100 as, polarization gating provides
access to the full bandwidth of the recolliding EWP and potentially enables
the generation of isolated pulses of few attoseconds. Isolated attosecond
pulses are thus becoming accessible in new spectral and temporal ranges and
will benefit to new attosecond science such as time resolved tomographic
imaging of electron wave packet motion or electron-electron interaction
dynamics at the atomic unit time scale.
[1] I. Sola, E. Mével, L. Elouga, E. Constant, V. Strelkov, L. Poletto, P
. Villoresi, E. Benedetti, J.-P. Caumes, S. Stagira, C. Vozzi, G. Sansone
and M. Nisoli, "Controlling attosecond electron dynamics by
phase-stabilized polarization gating", Nature Physics, 2, 319 (2006)
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