2,218 research outputs found
"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
Laser matter interaction in the bulk of transparent dielectrics: Confined micro-explosion
We present here the experimental and theoretical studies of drastic transformations induced by a single powerful femtosecond laser pulse tightly focused inside a transparent dielectric, that lead to void formation in the bulk. We show that the laser pulse energy absorbed within a volume of less than 1ÎĽm3 creates the conditions with pressure and temperature range comparable to that formed by an exploding nuclear bomb. At the laser intensity above 6 Ă— 1012 W/cm2 the material within this volume is rapidly atomized, ionized, and converted into a tiny super-hot cloud of expanding plasma. The expanding plasma generates strong shock and rarefaction waves which result in the formation of a void. Our modelling indicates that unique states of matter can be created using a standard table-top laser in well-controlled laboratory conditions. This state of matter has temperatures 105 K, heating rate up to the 1018 K/s, and pressure more than 100 times the strength of any solid. The laser-affected sites in the bulk were detected ("read") by generation of white continuum using probe femtosecond pulses at much lower laser intensity of 1010 W/cm 2 - 1011 W/cm2. Post-examination of voids with an electron microscope revealed a typical size of the void ranges from 200 to 500 nm. These studies will find application for the design of 3D optical memory devices and for formation of photonic band-gap crystals
Exactly solvable models : a solution to different problems of laser matter interaction
With the increasing use of ultrashort laser pulses and nanoscale-materials,
one is regularly confronted to situations in which the properties of the media
supporting propagation are not varying slowly with time (or space). Hence, the
usual WKB-type approximations fail, and one has to resort to numerical
treatments of the problems, with a considerable loss in our insight into the
physics of laser-matter interaction. We will present a new approach which
allows a fully analytical solution of such problems, based on a transformation
of the propagation equations into a new space where phase accumulation is
linear with either time or space, which greatly simplifies their treatment.
Though this method is restricted to some special models of the time or space
varying dielectric constant, those are however general enough to encompass
practically all experimental situations. It allows to introduce the concept of
"non-stationarity induced" (or "inhomogeneity induced") dispersion. We will
analyse the problem of reflection and propagation in two types of media whose
dielectric constant vary rapidly at either the laser period or the laser
wavelength scale. Extension of such techniques to the case of arbitrarily high
non linearities will be considered too
Ablation and Plasma Effects during Nanosecond Laser Matter Interaction in Air and Water
Despite extensive research work, a clear understanding of laser matter interaction i
Stepwise Precession of the Resonant Swinging Spring
The swinging spring, or elastic pendulum, has a 2:1:1 resonance arising at
cubic order in its approximate Lagrangian. The corresponding modulation
equations are the well-known three-wave equations that also apply, for example,
in laser-matter interaction in a cavity. We use Hamiltonian reduction and
pattern evocation techniques to derive a formula that describes the
characteristic feature of this system's dynamics, namely, the stepwise
precession of its azimuthal angle.Comment: 28 pages, 10 figure
Alternative gauge for the description of the light-matter interaction in a relativistic framework
We present a generalized velocity gauge form of the relativistic laser-matter
interaction. In comparison with the (equivalent) regular minimal coupling
description, this new form of the light-matter interaction results in superior
convergence properties for the numerical solution of the time-dependent Dirac
equation. This applies both to the numerical treatment and, more importantly,
to the multipole expansion of the laser field. The advantages of the
alternative gauge is demonstrated in hydrogen by studies of the dynamics
following the impact of superintense laser pulses of extreme ultraviolet
wavelengths and sub-femtosecond duration
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