Abstract: 

High-order harmonic generation is an extraordinary tool that allows for the production of high-frequency coherent radiation in the form of very short pulses that can be used to unveil the properties of matter at the nanoscale. High-order harmonic generation occurs during the interaction of an intense laser with the atoms in matter. First, the laser distorts the atomic potential, releasing the electron through tunnel ionization. Then, the electron is accelerated by the laser field and redirected to rescatter with its parent ion, leading to the emission of radiation in the form of harmonics of the incident laser’s frequency. In the spatial scale where this process occurs, the electrons behave as waves and, therefore, they experience some phenomena that are typically observed in light, like the Talbot effect. The (optical) Talbot effect leads to the formation of a series of self-images of a periodic field distribution —like that in a diffraction grating— at regular distances.

In this work, we simulate an experiment of matter Talbot imaging with the ionized electronic wavefunction in a crystal during the high-order harmonic generation. The periodic wavefunction in the crystal is released by the laser field and, upon its evolution, it experiences the formation of Talbot self-images over time. The temporal modulations in the harmonic signal, caused by the matter Talbot effect, leave a trace in the harmonic spectrum that depends on the band occupation of the crystal. Therefore, we propose a new spectroscopic tool, ultrafast Talbot spectroscopy, based on the already known Talbot -Lau interferometry.