  Relativistic mirrors can be realized with strongly nonlinear Langmuir waves
excited by intense laser pulses in underdense plasma. On reflection from the
relativistic mirror the incident light affects the mirror motion. The
corresponding recoil effects are investigated analytically and with
particle-in-cell simulations. It is found that if the fluence of the incident
electromagnetic wave exceeds a certain threshold, the relativistic mirror
undergoes a significant back reaction and splits into multiple electron layers.
The reflection coefficient of the relativistic mirror as well as the factors of
electric field amplification and frequency upshift of the electromagnetic wave
are obtained.
