High-harmonic generation from doped Si pumped with intense THz pulses

High-harmonic generation (HHG) is a phenomenon resulting from the strongly nonlinear, non-perturbative interaction between intense electromagnetic pulses and matter. It has been intensively investigated ever since its first observation with optically excited noble-gas atoms in the late 1980s [1] . The HHG effect is not only widely applied in table-top, coherent X-ray sources but is also the key for the generation of intense attosecond pulses [2] . Gases and atom clusters are the most intensively employed materials for HHG. Recently, HHG has also been observed in bulk crystals [3] , which has triggered a surge of research interest in HHG from solids [4] .