Generation and applications of high-order harmonics and attosecond pulses in solids

<p indent="0mm">High-order harmonic generation (HHG) has been realized by the strong-field non-perturbative interaction between intense ultra-short laser pulses and matter, which becomes the most effective way to generate attosecond pulses, and has been extended from gases to solids. For the first time, Ghimire et al. observed HHG in the non-perturbative region in ZnO in 2011. Solid-state HHG develops as a new approach for the next generation of compact extreme ultraviolet attosecond light sources and the exploration of ultrafast dynamic processes inside the condensed matter. Compared with gases, solid materials exhibit a characteristic of high density and complex spatial structure, hence the solid-state HHG involves a more complex generation mechanism. Firstly, this review summarizes the unique properties of solid-state HHG and demonstrates its differences from gas-state HHG. Then, it reviews the application scenarios of solid-state HHG and focuses on attosecond pulse generation based on solid-state HHG. Finally, we discuss the existing challenges and future exploration directions of solid-state HHG.