Extension of Harmonic Order by Applying the Interference of Pulses

A method is suggested to extend the order of harmonic generation from gas target by applying the interference effect of two pulses of which one is delayed with odd multiples of half-period relative to the other.It means the laser-atom interaction time can be shortened and the saturation intensity of laser-atom interaction is improved so that the atom can emit more higher-order harmonic.With the suggestion,one can extend the harmonic to the plateau cut-off predicted by harmonic generation theory.The numerical simulation gives some insights on this method.