Carrier-envelope phase measurement from half-cycle high harmonics

We present an efficient method to observe the high harmonics generated in individual half-cycle of the driving laser pulse by mixing a weak ultraviolet pulse, and then the cutoff of each half-cycle harmonic is imaged. The simulation shows that the information of the driving laser pulse, including the laser intensity, pulse duration and carrier-envelope phase, can be in situ retrieved from the harmonic spectrogram. In addition, our results show that this method also distinguishes the half-cycle high harmonics for a pulse longer than 10 fs, suggesting a potential to extend the CEP measurement to the multi-cycle regime.