Fig. 1: Field-resolved detection of charge-carrier motion controlled by sub-half-cycle photoinjection.

a, A schematic of the pump-probe measurements in which the waveform of the test pulse (red) was measured after transmission through a thin sample (orange) for different delays of the pump pulse (blue), which created charge carriers by multiphoton absorption. b, The nonlinear nature of the photoinjection confines its duration to a time interval shorter than the half wave-cycle of the test pulse, even for the weaker (two-photon) nonlinearity occurring in Si (shown in the panel). The green curve shows the nonlinear work performed by the pump field. The grey area highlights the time between the moments at which the work reaches 10% and 90% of its final value. In SiO₂, this confinement is even stronger owing to the higher number of photons needed for promoting a valence electron to the conduction band¹⁶.

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