Characteristics of relativistic electron mirrors generated by an ultrashort nonadiabatic
laser pulse from a nanofilm
Victor V. Kulagin,
1,
*
Vladimir A. Cherepenin,
2
Yuri V. Gulyaev,
2
Vladimir N. Kornienko,
2
Ki Hong Pae,
1
Victor V. Valuev,
3
Jongmin Lee,
1
and Hyyong Suk
1,4,†
1
Advanced Photonics Research Institute, GIST, Gwangju 500-712, Republic of Korea
2
Institute of Radioengineering and Electronics, RAS, Mohovaya 11, Moscow 125009, Russia
3
State R&D Laser Center “Raduga,” Raduzhnyi, Vladimir Region 600910, Russia
4
School of Photon Science and Technology, GIST, Gwangju 500-712, Republic of Korea
Received 3 November 2008; revised manuscript received 1 April 2009; published 13 July 2009
For controllable generation of an isolated attosecond relativistic electron bunch relativistic electron mirror
REM with nearly solid-state density, we proposed V.V. Kulagin et al., Phys. Rev. Lett. 99, 124801 2007
to use a solid nanofilm illuminated normally by an ultraintense femtosecond laser pulse having a sharp rising
edge nonadiabatic laser pulse. In this paper, the REM characteristics are investigated in a regular way for a
wide range of parameters. With the help of two-dimensional 2D particle-in-cell PIC simulations, it is shown
that, in spite of Coulomb forces, all of the electrons in the laser spot can be synchronously accelerated to
ultrarelativistic velocities by the first half-cycle of the field, which has large enough amplitude. For the process
of the REM generation, we also verify a self-consistent one-dimensional theory, which we developed earlier
cited above and which takes into account Coulomb forces, radiation of the electrons, and laser amplitude
depletion. This theory shows a good agreement with the results of the 2D PIC simulations. Finally, the scaling
of the REM dynamical parameters with the field amplitude and the nanofilm thickness is analyzed.
DOI: 10.1103/PhysRevE.80.016404 PACS numbers: 41.75.Jv, 41.75.Ht, 52.38.Kd
I. INTRODUCTION
Laser generation of attosecond relativistic electron beams
is currently a topic of very intense research. Attosecond elec-
tron beams can provide time-resolved studies in physics, bi-
ology, chemistry, etc., with the attosecond time-scale reso-
lution, which constitutes the main advantage of these beams.
Such beams can be used in a large variety of applications,
among them are attosecond physics and chemistry 1–3, ad-
vanced accelerators and free-electron lasers 4,5, different
technological applications, and many other fields. Besides,
with the help of ultrashort relativistic electron bunches,
bright ultrashort x-ray pulses can be generated using a Th-
omson backscattering of the probe laser beam 6. Such
pulses are particularly useful for x-ray spectroscopy 7,8
and other applications 9. If a length and a spread of the
electron momenta for an ultrashort electron beam can be
small enough, then even coherent x-ray pulses can be gener-
ated, which can also be used in many fields 10–12. In all
applications, one needs to control precisely the parameters of
the attosecond electron beams, including their length, charge,
mean energy, energy spread, and so on.
In high-density overcritical plasmas, two mechanisms
for generation of ultrashort electron beams—the v B heat-
ing and the vacuum heating—were investigated by two-
dimensional 2D particle-in-cell PIC simulations 13,14
and were confirmed by experiments 15,16 recently. Here,
Lorentz force ejects electrons one or two times per laser
period out of plasma reflection mode or accelerates elec-
trons in the low-density preplasma in the direction of the
laser pulse with their subsequent penetration through the
bulk plasma transmission mode. Electron ejection and ac-
celeration are irregular in this mechanism, thus explaining
the wide energy spread of generated electrons and difficulties
with controlling the beam parameters. The length of the elec-
tron beam here is about the laser pulse length, besides, the
electron beam has a typical microbunching tapering of den-
sity having laser or half-laser wavelength period train of
electron microbunches. The practical possibility for isola-
tion of a single microbunch is not evident here.
In low-density underdense plasmas, ultrashort electron
beams can be generated by laser wake field acceleration
mechanism 4,17,18. A single electron bunch can be pro-
duced here, but the length of the bunch is usually not shorter
than 3–5 m tens of femtoseconds. In a vacuum, a single
ultrashort electron beam can be generated through laser com-
pression of a longer electron beam see, e.g., test particle
19 and one-dimensional 1D PIC 20,21 simulations.
However, the charge of the bunch here is considerably
smaller than 1 pC. The same compression can be applied
for thin 1 m and less plasma layers of low gas density
1D calculations 22–24, but the practical realization of
such layers is under question now.
We proposed earlier 25 to use a nanofilm film with a
thickness of 10 nm or less as a solid-state density target for
generation of an attosecond relativistic electron bunch. It
was shown that, when this target is irradiated normally by a
superhigh intensity laser pulse with a sharp rising edge
nonadiabatic laser pulse, all electrons of the plasma layer
can achieve relativistic longitudinal velocities synchronously
when the dimensionless field amplitude becomes large
enough, a
0
a
0
= |e|E
0
/ mc, =
p
2
/
2
l / , where
*
Present address: Sternberg Astronomical Institute of Moscow
State University, Universitetsky prosp. 13, Moscow, Russia.
victorvkulagin@yandex.ru
†
Corresponding author. hysuk@gist.ac.kr
PHYSICAL REVIEW E 80, 016404 2009
1539-3755/2009/801/01640412 ©2009 The American Physical Society 016404-1