Autocorrelation Measurement of Attosecond Pulses Based on Two-Photon Double Ionization

Autocorrelation measurement is theoretically demonstrated to characterize attosecond pulses by studying the two-photon double ionization (TPDI) process. An interferometric autocorrelation curve is presented in the change of TPDI probability with the time delay between two identical attosecond pulses, and its full width at half maximum (FWHM) $\tau_{e}$ has a relationship $\tau_{e}=1.77\tau+15$ with the FWHM $\tau$ of the attosecond pulse. The curve is also decoded to obtain the center frequency and FWHM of the attosecond pulse by fitting. In addition, the required peak intensity of the attosecond pulse is estimated to be on the order of $10^{16}\,\rm{Wcm^{-2}}$ in autocorrelation experiments. The findings pave the way for autocorrelation measurement of intense isolated attosecond pulses.