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A new technique for directly measuring the electric field of linearly polarized few-cycle laser pulses is proposed. Based on the solution of the time-dependent Schrödinger equation (TDSE) for an H atom in the combined field of infrared (IR) femtosecond (fs) and ultraviolet (UV) attosecond (as) laser pulses we show that, as a function of the time delay between two pulses, the difference (or equivalently, asymmetry) of photoelectron signals in opposite directions (along the polarization vector of laser pulses) reproduces very well the profile of the electric field (or vector potential) in the IR pulse. Such ionization asymmetry can be used for directly measuring the carrier-envelope phase difference (i.e., the relative phase of the carrier frequency with respect to the pulse envelope) of the IR fs laser pulse.

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AbslracL Ihe dynamic localization of electrons induced simultaneously by DC and AC electric helds in the classical limit is investigated. Scattering processes are taken into account. I t is shown that the localization induced by one field cdn be suppressed by another one when nR = w (w is the Stark frequenc, and R is the AC held frequenq).Ihe localization is also effectively deslmyed by sfaltering processes.It is well known that, in the uniform electric field E, the electron motion in a periodic potential undergoes Bloch oscillations with the Stark frequency w = eEa (where a is the period of the potential and h = 1). In the quantum limit, when w > A (A is the allowed band width), the Bloch oscillations manifest themselves in the form of discrete eigenstates in the electron energy spectrum (Stark ladder). The wavefunction of the Stark-ladder states is found to be localized (see for example [1,2] and references therein). This phenomenon is called dynamic localization.