Strong-field photoionization and the absolute phase of few-cycle laser pulses

We present the first experimental evidence for an effect of the absolute phase. Atoms are ionized by a short laser pulse and the electrons leaving the ion core are registered with two detectors facing each other on opposite sides of the laser beam. Thus, each laser pulse can be characterized by the number of electrons emitted to the left and the right. Accordingly, the laser shots are recorded in a contingency map. Due to the absolute phase, a laser shot that produces a lot of electrons flying to the right has a high probability to produce only a few flying to the left. This anticorrelation becomes visible as a structure perpendicular to the diagonal.