- Letter
Microscopic mechanisms of high-order wave mixing in solids
Phys. Rev. A 108, L051103 – Published 20 November, 2023
DOI: https://doi.org/10.1103/PhysRevA.108.L051103
Abstract
The gas-phase technique of noncollinear two-color excitation is adapted to study extreme-ultraviolet high-order harmonic generation (HHG) in magnesium oxide. We observe high-order wave-mixing pathways with brightness comparable to that of the single-color HHG. Simulations reveal that the efficiencies are dominated by the microscopic physics as opposed to macroscopic effects. Building on previous work, we develop a general analytic theory of high-order wave mixing that explains our observations and demonstrates how a perturbative nonlinear optical framework emerges form the interaction between the weak field and the laser-dressed state of the crystal in the strong-field approximation. The theory outlines a photon-mixing picture of high-order wave mixing and connects the strong asymmetry between sum- and difference-frequency pathways to the cutoff in the HHG spectrum. Our work establishes the potential of high-order wave mixing as a probe of the microscopic attosecond physics in solids and points to new opportunities in solid-state strong-field photonics.
