Carrier envelope phase retrieval of a multi-cycle pulse by heterodyne mixing of a pulse containing a few cycles

Abstract

We present a theoretical routine for carrier envelope phase (CEP) retrieval of a multi-cycle femtosecond pulse by heterodyne mixing with a CEP-known few-cycle pulse using the time-dependent wavepacket quantum dynamics method. Our study is based on the CEP measuring technique and the dependence of high-order harmonic generation (HHG) spectra on CEP. After heterodyne mixing, half-cycle cutoffs (HCOs) in HHG spectra become distinct when the CEPs of multi-cycle and few-cycle pulses are well matched. The well-matched CEP of the heterodyne mixing field has a significant effect on the HHG spectra. Moreover, both quantum analysis and classical calculations are performed to demonstrate our theoretical results. The extension of CEP measurement from few-cycle pulses to multi-cycle pulses strengthens the controllability of laser parameters for femtosecond pulses.