The interaction of strong near-infrared (NIR) laser pulses with wide-bandgap dielectrics produces high harmonics in the extreme ultraviolet (XUV) wavelength range. These observations have opened up the possibility of attosecond metrology in solids, which would benefit from a precise measurement of the emission times of individual harmonics with respect to the NIR laser field. Here we show that, when high-harmonics are detected from the input surface of a magnesium oxide crystal, a bichromatic probing of the XUV emission shows a clear synchronization largely consistent with a semiclassical model of electron-hole recollisions in bulk solids. On the other hand, the bichromatic spectrogram of harmonics originating from the exit surface of the 200 μm-Thick crystal is strongly modified, indicating the influence of laser field distortions during propagation. Our tracking of sub-cycle electron and hole re-collisions at XUV energies is relevant to the development of solid-state sources of attosecond pulses.
Publication Source (Journal or Book title)
Journal of Physics B: Atomic, Molecular and Optical Physics
Vampa, G., Lu, J., You, Y., Baykusheva, D., Wu, M., Liu, H., Schafer, K., Gaarde, M., Reis, D., & Ghimire, S. (2020). Attosecond synchronization of extreme ultraviolet high harmonics from crystals. Journal of Physics B: Atomic, Molecular and Optical Physics, 53 (14) https://doi.org/10.1088/1361-6455/ab8e56