Fig. 1: Experimental approach.

a Cross–correlation method used for the temporal characterization of the harmonics generated by the interaction of intense few-cycle CEP stable M–IR pulses with ZnO crystal. The harmonic and the M–IR fields are spatiotemporally overlapped in the Cs gas. The delay stage was used to control the time delay τ between the harmonics and the M–IR dressing field. BS and c–BSt, are an M-IR beam splitter and an M–IR central beam block, respectively. FM1,2 are focusing mirrors of 50 cm and 15 cm focal length, respectively. The generated photoelectrons are recorded by a μ–metal-shielded time–of–flight (TOF) spectrometer. b Spectrogram which shows the dependence of the photoelectron spectrum on the delay between the VUV and M-IR fields.