Single-shot carrier-envelope phase measurement of few-cycle laser pulses

Full characterization of single ultrashort laser pulses, as needed for attosecond metrology and spectroscopy, requires precise measurement of the offset between the electric field and pulse envelope, or carrier-envelope phase (CEP). Until now, all CEP measurements have been made by averaging over a large number of phase-stabilized laser pulses. Here, we demonstrate the first single-shot CEP measurement of intense few-cycle laser pulses. We focus a laser pulse on a gas target and detect photoelectrons emitted in opposing directions ('left-right') parallel to the polarization of the laser. By comparing the left-right asymmetries of photoelectrons at different energies, we mapped the CEP of consecutive non-phase-stabilized pulses on a parametric plot. This new evaluation method enables us to determine the CEP without phase ambiguity at unprecedented measurement precision. Future investigation of phase-dependent phenomena with CEP tagging at a much lower phase jitter than accessible at present with phase-stabilized lasers is now possible.