Y. You, D. A. Reis, S. Ghimire, P.H. Bucksbaum, J. N. Clark, M. Fuchs, T. E. Glover, J. M. Glownia , J. B. Hastings, S. Shwartz, M. Trig

Stanford University - PULSE Institute; SLAC National Accelerator Laboratory

There is growing evidence that high-harmonic generation and other nonperturbative strong-field effects in solids involves coherent attosecond electron motion.  However, most strong field experiments only probe the macroscopic properties (emission, absorption, etc.).  The high flux of the free-electron laser could be used to image these processes on their natural length and time-scale.

Parametric x-ray processes in principle allow us to measure the microscopic response of materials to optical and XUV fields with high atomic resolution (Freund 1970; Eisenberger 1971).  Seminal experiments by Tamasaku et al., (Tamasaku 2011) and Glover et al., (Glover 2012) use this effect to measure the linear optical response via down conversion and sum frequency respectively.

Here we propose to use higher-order sum and difference frequency generation to image the spatio-temporal dynamics of the charges involved in solid-state high-harmonic generation (Ghimire 2011).   As wave-mixing is a coherent inelastic scattering process, by Fourier analysis of the dynamical structure factors associate with high-order sidebands, we can reconstruct the dynamics with Angstrom spatial and attosecond temporal resolution.