Method to generate directly a broadband isolated attosecond pulse with stable pulse duration and high signal-to-noise ratio

摘要

A method to generate a broadband isolated attosecond pulse with stable pulse duration and high signal-to-noise ratio is proposed. By adopting a few-cycle driving pulse combined with its second-harmonic field of which the polarization angle is pi/3 with respect to the driving pulse, the short path is well selected and a smooth supercontinuum with the bandwidth of about 50 eV is observed, which leads to 100-as single attosecond pulse generation with high signal-to-noise ratio. More surprisingly, the intensity variation of the second-harmonic field can hardly affect the location and the bandwidth of the generated supercontinuum but only slightly reduce its phase-locking degree. For the intensity of the second-harmonic field higher than 10(14) W/cm(2), a pure isolated attosecond pulse with duration of about 100 as can be generated by directly filtering out a supercontinuum from 85-125 eV, which facilitates the experimental implement of the isolated attosecond pulse generation.