Generation of the isolated attosecond pulse by using the two-color chirped pulse

We theoretically investigate the combined chirp effects on the generation of the high-order harmonic and the isolated attosecond pulse when a model He atom is exposed to an intense 5 fs/800 nm fundamental chirped pulse combined with a weak 10 fs/1600 nm controlling chirped pulse. The results show that when the chirped parameters are chosen to be β₁ = 0.3 and β₂ = 0.6, the harmonic cutoff energy is remarkably enhanced. Further, through optimizing the laser parameters from the carrier-envelope phases(CEPs) and the pulse intensity, the harmonic cutoff is extended to the 812 eV. Finally, by superposing a properly selected harmonics in the supercontinuum region, a series of isolated attosecond pulses with durations of 33 as can be obtained. (author)