Measurement of the carrier-envelope phase of few-cycle laser pulses by use of asymmetric photoionization

Using numerical solutions of the time-dependent Schrödinger equation for a hydrogen and a helium atom in a linearly polarized, few-cycle laser field, we calculate the photoelectron left–right asymmetry measured by two opposing detectors placed along the laser polarization vector, with the laser focus in the center. We find a simple dependence of this asymmetry on carrier-envelope (CE) phase $\varphi$ for laser intensities slightly below the tunneling regime, which may allow us to measure (or to calibrate) and to stabilize the CE phase. In particular, we suggest that the condition of zero asymmetry for few-cycle pulses may be useful for both these goals.