8,112 research outputs found
Features of ion acceleration by circularly polarized laser pulses
The characteristics of a MeV ion source driven by superintense, ultrashort
laser pulses with circular polarization are studied by means of
particle-in-cell simulations. Predicted features include high efficiency, large
ion density, low divergence and the possibility of femtosecond duration. A
comparison with the case of linearly polarized pulses is made.Comment: 4 pages, 4 figure
Few-cycle Surface Plasmon Polariton Generation by Rotating Wavefront Pulses
A concept for the efficient generation of surface plasmon polaritons (SPPs)
with a duration of very few cycles is presented. The scheme is based on grating
coupling and laser pulses with wavefront rotation (WFR), so that the resonance
condition for SPP excitation is satisfied only for a time window shorter than
the driving pulse. The feasibility and robustness of the technique is
investigated by means of simulations with realistic parameters. In optimal
conditions, we find that a ~fs pulse with ~nm wavelength can excite
a ~fs SPP ( laser cycles) with a peak field amplitude
times the peak value for the laser pulse
Two-surface wave decay: improved analytical theory and effects on electron acceleration
Two-surface wave decay (TSWD), i.e. the parametric excitation of electron
surface waves, was recently proposed as an absorption mechanism in the
interaction of ultrashort, intense laser pulses with solid targets. We present
an extension of the fluid theory of TSWD to a warm plasma which treats boundary
effects consistently. We also present test-particle simulations showing
localized enhancement of electron acceleration by TSWD fields; this effect
leads to a modulation of the current density entering into the target and may
seed current filamentation instabilities.Comment: 4 figures, submitted to Appl.Phys.B (special issue from HFSW X
conference, Biarritz, France, Oct 12-15 2003); slightly revised tex
Vlasov simulation of laser-driven shock acceleration and ion turbulence
We present a Vlasov, i.e. a kinetic Eulerian simulation study of nonlinear
collisionless ion-acoustic shocks and solitons excited by an intense laser
interacting with an overdense plasma. The use of the Vlasov code avoids
problems with low particle statistics and allows a validation of
particle-in-cell results. A simple original correction to the splitting method
for the numerical integration of the Vlasov equation has been implemented in
order to ensure the charge conservation in the relativistic regime. We show
that the ion distribution is affected by the development of a turbulence driven
by the relativistic "fast" electron bunches generated at the laser-plasma
interaction surface. This leads to the onset of ion reflection at the shock
front in an initially cold plasma where only soliton solutions without ion
reflection are expected to propagate. We give a simple analytic model to
describe the onset of the turbulence as a nonlinear coupling of the ion density
with the fast electron currents, taking the pulsed nature of the relativistic
electron bunches into account
Two-Surface Wave Decay
Using an analytical model we discuss the parametric excitation of pairs of
electron surface waves (ESW) in the interaction of an ultrashort, intense laser
pulse with an overdense plasma which has a step-like density profile. The ESWs
can be excited either by the electric or by the magnetic part of the Lorentz
force exerted by the laser and, correspondingly, have frequencies around
or , where is the laser frequency.Comment: 4 EPS figures, Revte
"Single-cycle" ionization effects in laser-matter interaction
We investigate numerically effects related to ``single-cycle'' ionization of
dense matter by an ultra-short laser pulse. The strongly non-adiabatic response
of electrons leads to generation of a megagauss steady magnetic field in
laser-solid interaction. By using two-beam interference, it is possible to
create periodic density structures able to trap light and to generate
relativistic ionization frontsComment: 12 pages, 6 figures, to be published in Laser and Particle Beam
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