The effect of nonlinear chirp combination on the enhancement of harmonic cutoff and harmonic intensity has been investigated by using a two-color chirped pulse. It is found that with the combination of 2-order chirp form, the strongest intensity enhancement of harmonic spectrum can be found. While, with the combination of 2-order and 3-order chirp forms, the largest cutoff extension of the harmonic spectrum can be obtained. Finally, by properly using the harmonic spectra driven by the above two kinds of combined pulses, the single attosecond pulses (SAPs) of 43 as and 33 as can be generated.
Relativistic plasma aperture for laser intensity enhancement