Observable manifestation of an electron-positron plasma created by the field of an optical laser

Electron-positron vacuum pair creation in the quasi-periodic electric field of a standing wave is investigated for field strengths and frequencies corresponding to modern optical lasers using a quantum kinetic equation with a non-markovian source term. For a field E ∼ 5 · 1011 V/cm, the instantaneous quasiparticle electron-positron plasma is created which maximum density of order 1020cm−3. The mean value of the pair density per period exceeds by many orders of magnitude the residual density nr which is taken over an integer number of field periods. The value is proportional to the squared field intensity and does not depend on the frequency at ν m. Under conditions of presently available optical lasers with intensities exceeding I ∼ < 1020W/cm2, the mean number of created pairs in the volume of a wavelength cubed is about 107 which corresponds to 5 - 10 two-photon annihilation events per one laser pulse. The generated γ-quanta are suggested to be an observable signal of e+ e− pair vacuum creation in experiments with counter-propagating optical laser beams.