Dynamics via Attosecond Four-Wave Mixing

Attosecond four-wave mixing spectroscopy is a relatively new technique for studying ultrafast dynamics of highly excited states with exquisite temporal precision and spectral resolution. The attosecond four-wave mixing technique, as described in this paper, uses non-collinear beam geometries of one attosecond pulse together with two optical pulses to obtain background-free, spatially isolated emission signals in the extreme ultraviolet range that directly resolve coherent dynamics in the time domain. This method is advantageous by avoiding the strong spectral modulations that often complicate the interpretation of collinear attosecond transient absorption studies while also enabling greater control over the spatial and temporal characteristics of each light-matter interaction used to probe the ultrafast processes. This paper describes a broad range of attosecond four-wave mixing experiments performed in gas phase atoms and molecules, and a recent extension into solids.