Formation of relativistic electron mirrors in laser-plasma interactions

The generation of relativistic electron mirrors (bunches with extremely short lengths) in laser-plasma interactions is considered. It is shown that such a mirror can be generated by using an ultra-intense nonadiabatic laser pulse (pulse with a sharp rising edge) incident normally upon a thin plasma layer. Due to the relativistic contraction, the resulting length of the electron mirror can be considerably smaller than the initial thickness of the plasma layer. The lifetime of the relativistic mirror depends on the dimensionless amplitude and shape of the laser pulse, the initial density of electrons, and the thickness of the plasma layer. As a result, relativistic electron, mirrors can survive during the first several half-periods of an external electromagnetic field, which can correspond to time intervals of hundreds of femtoseconds in the laboratory frame.