Session CO2 - Laser Accelerators; Ultraintense Laser Applications.
ORAL session, Monday afternoon, November 15
Room 203, SCC
We report on a numerical observation of the train of zeptosecond pulses produced by reflection of an relativistically intense femtosecond laser pulse from the oscillating boundary of an overdense plasma because of the Doppler effect. These pulses promise to become a unique experimental and technological tool since their length is of the order of the Bohr radius and the intensity is extremely high \propto 10^19~W/cm^2. We present the physical mechanism, analytical theory, and direct particle-in-cell simulations. We show that the harmonic spectrum is universal: the intensity of nth harmonic scales as 1/n^p for n < 4\gamma^2, where \gamma is the largest \gamma--factor of the electron fluid boundary, p=3 and p=5/2 for the broadband and quasimonochromatic laser pulses respectively.