Intense X-ray isolated attosecond pulse generation by using low-intensity chirped pulse combined with a UV seeding pulse

Abstract

We theoretically investigate intense isolated attosecond pulse (IAP) generation from high-order harmonic generation (HHG) driven by a low-intensity chirped pulse combined with a UV seeding pulse. The results show that, driven by a two-color chirped pulse, the harmonic cutoff can be remarkably extended and a spectral continuum in X-ray region can be obtained. Moreover, as the pulse duration increases or the delay time of the two pulses changes, a larger harmonic cutoff can be found. Further, with the introduction of a UV seeding pulse, the efficiency of HHG can be enhanced by three orders of magnitudes due to the UV resonance ionization. Moreover, as the UV pulse intensity increases, the enhanced ratio of HHG yield can be further improved. The enhancement of HHG yield is related to the pulse duration and delay time of the UV pulse. For instance, when adding a shorter duration UV pulse, the enhancement of HHG is dependent on the delay time of the UV pulse. However, when adding a longer duration UV pulse, the HHG enhancement is not very sensitive to the delay time of the UV pulse. Finally, the obtained spectral continuum supports the generation of intense IAP with the duration of 36 as.