Low-energy peak structure in strong-field ionization by mid-infrared laser-pulses: two-dimensional focusing by the atomic potential

We analyze the formation of the low-energy structure (LES) in above-threshold ionization spectra first observed by Quan et al.\ \cite{quan09} and Blaga et al.\ \cite{blaga09} using both quasi-classical and quantum approaches. We show this structure to be largely classical in origin resulting from a two-dimensional focusing in the energy-angular momentum plane of the strong-field dynamics in the presence of the atomic potential. The peak at low energy is strongly correlated with high angular momenta of the photoelectrons. Quantum simulations confirm this scenario. Resulting parameter dependences agree with experimental findings \cite{quan09,blaga09} and, in part, with other simulations \cite{liu10,yan10,kast11}.Comment: 12 pages, 6 figure

Self-compression of sub-TW mid-IR pulses in transparent dielectrics and filaments generated in ambient air

We report on self-compression of sub-100 fs, >20 mJ md-IR pulses in transparent dielectrics and filaments ignited in ambient air. Combination of both permits generation of TW-level homogeneously compressed two-optical-cycle mid-IR pulses