Last thirty years of strong-field physics has focused on understanding the fundamental response of isolated atoms and molecules to intense infrared laser fields. This understanding has been the foundation of much of extreme non-linear optics including attosecond pulse generation and imaging molecular orbitals. Following that success, we have begun to study fundamental strong-field response in dense optical media such as bulk crystals. Already, our first sets of experimental results reveal novel solid-state effects. In this talk, I will present our new results on high-harmonic generation from solids, particularly focusing on the similarities and differences to the gas-phase [e.g. Nature Physics 13, 345, 2017 and Nature 534, 520, 2016]. Unique features of solid-state harmonics include high-energy cutoff that scales linearly with the field, observation of multiple plateaus, and rich ellipticity dependence. Our results indicate that high-harmonics could also probe electronic structure of solids, in particular the possibility of all-optical methods to image valance charge density may be within reach. Other implications include generation of attosecond pulses with polarization control in a compact experimental setup.
