Metering the absolute phase of a few-cycle pulse via its high-order above-threshold ionization spectrum
The influence of the carrier-envelope phase (``absolute phase'') of a few-cycle pulse on the left-right asymmetry of the photoelectron spectrum of high-order above-threshold ionization is analyzed. Energy spectra are calculated for opposite detectors along the polarization axis of a linearly polarized four-cycle laser pulse. The results obtained allow us to determine the value of the absolute phase in a given experiment by comparison with the theoretical spectra. A classical analysis of the calculated spectra is presented, and the corresponding electron trajectories are analyzed. Emission of high-energy electrons is found to occur in one or two ultrashort subfemtosecond bursts.