Interferometry of an attosecond pulse train generated from Xe gas target

► We have demonstrated the interferometry of extreme ultraviolet attosecond pulse train (APT). ► A spatial split autocorrelator is the crucial device for implementing the experiment. ► The Fourier spectrum of each harmonic field in the APT agrees well with the measured spectrum. ► The definite symmetry of the APT interference fringes is also revealed.