Retrieval of the dephasing time in solids from spatial high-harmonic spectroscopy

The ultrashort dephasing time in solid-state high-order harmonic generation (HHG) is an essential parameter for understanding its microscopic and macroscopic generation processes. However, precise measurement of this parameter is very challenging with current experimental techniques. Here, we propose a model-based method to reconstruct the dephasing time in solids using spatial high-harmonic spectroscopy. We employ spatial harmonic profiles simulated from the solution of the microscopic semiconductor Bloch equations, and the Hankel transform to account for the far-field propagation of the emitted harmonics in vacuum as simulated-measurement (input) data. We develop an analytical procedure to predict the far-field spatial harmonic profile from microscopically separated quantum trajectories, in which the dephasing time is encoded. Based on this procedure, we show that, under the conditions considered here, the dephasing time can be retrieved to within 0.1 optical cycles. We also assess the robustness of the retrieval method against variations in the laser wavelength and intensity within the parameter range considered for the present monolayer ZnO model. The present quantitative validation is restricted to the monolayer ZnO thin-source geometry and relies on material-specific information obtained from microscopic modeling. This work not only provides a novel approach for measuring the dephasing time but also offers a new perspective for the in-depth exploration of the underlying microscopic and macroscopic physical generation mechanisms in solids under strong laser fields.