Phase-sensitive plasma nonlinearity controlled by ultrashort pulses

The generation of spectral components sensitive to the carrier-envelope phase of a laser pulse in a thin zinc selenide film has been experimentally demonstrated and confirmed by a numerical simulation. A pump–probe scheme has been implemented so that a pump pulse with a duration of about 1.5 field cycles, a central wavelength of 1.7 $\mu$m, and a stabilized carrier-envelope phase induces photoionization in a thin zinc selenide film. The probe pulse is scattered by the plasma, generating new phase-sensitive spectral components at the edges of its spectrum. The theoretical analysis has confirmed plasma nonlinearity as a mechanism for generating these components. The observed effect can be used to characterize the carrier-envelope phase of ultrashort pulses during the generation of high-order harmonics and sequences of attosecond pulses.