Ponderomotive laser acceleration and focusing in vacuum for generation of attosecond electron bunches.

A novel approach for the generation of ultrabright attosecond electron bunches is proposed, based on acceleration in vacuum, by a short laser pulse. The laser-pulse profile is tailored such that the electrons are both focused and accelerated by the ponderomotive force of the light. Using time-averaged equations of motion, analytical criteria for optimal regime of acceleration are found. It is shown that for realistic laser parameters, a beam with up to 10(6) particles and normalized transverse and longitudinal emittances <10(-8) m can be produced.