Giant half-cycle attosecond pulses

Half-cycle picosecond pulses have been produced from thin photoconductors when applying an electric field across the surface and switching on conduction using a short laser pulse. The transverse current in the wafer plane then emits half-cycle pulses in a normal direction, and pulses of 500 fs duration and 1 x 10(6) Vm(-1) peak electric field have been observed. Here, we show that single half-cycle pulses with a duration of 50 as and up to 1 x 10(13) Vm(-1) can be produced when irradiating a double foil target with intense few-cycle laser pulses. Focused onto an ultrathin foil, all electrons are blown out, forming a uniform sheet of relativistic electrons. A second layer, placed some distance behind, reflects the drive beam but lets electrons pass straight through. Under oblique incidence, beam reflection provides the transverse current, which emits intense half-cycle pulses. Such a pulse may completely ionize even heavier atoms. With these developments, new types of attosecond pump-probe experiments will become possible.