Mapping Electric Fields in Space and Time with Solid-State High Harmonic Generation
POSTER
Abstract
Even-order harmonics, which are normally forbidden in centrosymmetric media, can be produced in the presence of a symmetry-breaking electric field. This principle has long been known in the perturbative regime, where electric fields can enable second harmonic generation.We demonstrate the extension of this technique to the non-perturbative regime, showing that high-order harmonics allow us to measure electric fields in solid matter. We illuminate Si and ZnO samples with ultrafast mid-infrared pulses, with intensity on the order of $1~\rm{TW}/\rm{cm}^2$. Symmetry-breaking fields are provided by voltage pulses applied to electrodes at the semiconductor surfaces, or, in a second experiment, by a THz transient. The even harmonic emission measures the electric field in time, with sub-picosecond temporal resolution. In addition, we can image even harmonics to reveal the spatial distribution of fields. The technique is a flexible all-optical probe of fields, which can combine high spatial and temporal resolution.