  An overdense plasma layer irradiated by an intense light can exhibit dramatic
nonlinear-optical effects due to a relativistic mass-effect of free electrons:
highly-multiple hysteresises of reflection and transition, and emergence of
gigantic "rogue waves". Those are trapped quasi-soliton field spikes inside the
layer, sustained by an incident radiation with a tiny fraction of their peak
intensity once they have been excited by orders of magnitude larger pumping.
The phenomenon persists even in the layers with "soft" boundaries, as well as
in a semi-infinite plasma with low absorption.
