Carrier-envelope phase measurement using a non phase stable laser

We demonstrate that the phase between the carrier and the pulse envelope of a few-cycle laser pulse can be retrieved from non phase stable laser systems, provided that such laser pulses are about 5 fs long and the repetition rate is in the order of 1 kHz. Our approach is based on online determination of the phase using f-2f interferometry. By a comparison of the self referencing interferometric signal with the photoelectron current emitted into a 7 degree solid angle parallel to the laser polarization, we obtain the absolute value of the carrier envelope phase. This is provided that a Coulomb correction for electron energies below 10 eV can be correctly taken into account.