  We review recent PIC simulation results which show that double-sided
irradiaton of a thin overdense plasma slab by ultra-intense laser pulses from
both sides can lead to sustained comoving acceleration of surface electrons to
energies much higher than the conventional ponderomotive limit. The
acceleration stops only when the electrons drift transversely out of the laser
beam. We show results of parameter studies based on this concept and discuss
future laser experiments that can be used to test these computer results.
