Fig. 1. (IMAGE)
Caption
Fig. 1. Influence of the drive pulse temporal envelope and its waveform on the formation
of the electron mirror and backscattered signal. The 40-nm-thick plasma slab (located
from 6휆L to 6.05휆L ) is irradiated by drive pulses possessing different waveforms and
temporal envelopes, (A) top-hat, (B) Gaussian, and (C) optimal dual-color Gaussian
(with P = 0.4) pulses, which causes various temporal evolutions of electron number
density. In all cases, the drive beam propagates from left to right and is incident normally
on the 40-nm-thick pre-ionized plasma foil at 6TL . (D) compares the temporal waveforms
of the single- (1휔) and 2-color (1휔 + 2휔) drive Gaussian pulses with end-to-end 12TL
temporal duration and polarization along the y-direction. The inset at the lower left
hand side enlarges the waveforms from 4TL to 5TL , highlighting the steepness of the
accelerating 2-color field. The counterpropagating source pulse with a duration of
6TL and a peak amplitude of a0 = 0.1 interacts with the electron sheet and reflects
partially. The squared field of the normalized Thomson backscattering (TBS) signals
are shown in (E), indicating the generation of a single 110-as pulse (in the full width at
half-maximum [FWHM]) in the case of a ( 1휔+2휔 ) drive beam. The duration of the TBS
signal, resulting from interaction with the produced relativistic electron sheet (RES) in
panel (A) is 380 as. This pulse is scaled by a factor of 10 (in blue). The reflected pulses
are temporally shifted for better comparison. The corresponding frequency spectra of
the TBS radiations are illustrated in panel (F). The attosecond pulse (AP) generated by
the interaction of the dual-color drive beam and foil target is composed of a spectrum
peaking at 26휔L .
Credit
Ultrafast Science
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