The carrier-envelope-phase (CEP) plays an important role in extreme nonlinear effects, when the duration of the pulse is comparable to the optical field oscillation. Researchers in the Sate Key Laboratory of High Field Laser Physics of Shanghai Institute of Optics and Fines Mechanics (SIOM/China) and Politecnico di Milano (POLIMI/Italy) cooperatively propose a novel scheme for the measurement of the CEP of the single attosecond pulse, which has been published in Phys. Rev. Lett. 111, 123901 (2013).

Even though the traditional attosecond streak camera has allowed the demonstration of single-cycle attosecond waveform, it does not provide information about its CEP. The FROG-CRAB method and other techniques proposed for the characterization of attosecond pulses, allow one to retrieve the XUV spectral phase within an arbitrary constant, which leaves the CEP undefined in the time domain.

It is demonstrated that information on the CEP of isolated attosecond pulses can be obtained by measuring the photoelectron spectra emitted by the combination of a XUV attosecond field and a CEP-stable IR pulse with an intensity higher than the one typically used for the temporal characterization of attosecond waveforms. The investigation for the dependence of the photoelectron distribution on the CEP of the XUV pulse shows that above-treshold ionization (ATI) electrons can be used as a reference to highlight variations in the CEP of the attosecond pulse. The key idea based on the interference between the re-scattered electrons generated by the infrared field and the attosecond electron wave packet created by single photon ionization pave the way in the complete characterization of the temporal electric field of the attosecond pulse.