Konwersatorium im. Leopolda Infelda

In the last decade the increasing availability of Terra- and Petawatt class lasers with ps to fs pulse duration has intensified the interest in the relativistic interaction between laser radiation and matter. Today laser intensities of up to 1022 W/cm2 can be achieved routinely, delivering field strengths at which electrons become ultra-relativistic within a single cycle of the optical field. Via the interaction of such intense fields with plasma it is possible to generate electric and magnetic fields inside plasma of the order of TV/m and kilo-Tesla, respectively. This leads to several promising applications such as compact particle and radiation sources.
Laser pulses with power on the Exawatt/Zettawatt scale would not only improve current applications, but would open the door to access new regimes, e.g. direct access to the QED vacuum via the optical fields. Most high-intensity lasers today rely on the Chirped Pulse Amplification (CPA) scheme that can only hardly be scaled to these power levels due to material damage thresholds. A novel approach that allows circumventing these issues is the use of plasma as an amplification medium. Plasma oscillations (electron Langmuir waves or Ion oscillations) may be used as optical gratings, scattering the energy from a long pump pulse into a short seed pulse. Plasma-based pulse amplification is currently discussed as a prospective key component of the next generation high-intensity laser pulses.
The first part of the presentation introduces into the field of relativistic laser-plasma interaction and highlights the current research activities such as generation of GeV electron beams via wake-field acceleration, MeV proton acceleration from overdense plasma target interaction and generation of atto-second X-ray radiation.
In the second part of the presentation the theory of plasma-based laser-pulse amplification will be discussed. It will be shown that two types of amplifiers, Raman or Brillouin, are possible. The former uses electron plasma oscillations, the latter ion plasma oscillations to transfer energy from the pump pulse into the seed pulse. For both types, the present situation and future perspectives will be discussed.