Angular dependence of non-perturbative VUV harmonics in silicon

The observation of high harmonic generation(HHG) in ZnO in 2011 has opened new doors in the fields of ultrafast spectroscopy and sub-optical-cycle electron dynamincs in solid state materials [1] . The main mechanisms behind the radiation are interband and intraband dynamics, but their contributions remain unclear. The generated radiation can be used to probe the crystal and electronic band structure of the materials on ultrafast time scales. Previous experiments have explored mostly the visible-ultraviolet (wavelength range 200-1000 nm) and extreme ultraviolet (wavelength < 80 nm) spectral region using THz and MIR driving lasers, but the vacuum ultraviolet (VUV) spectral region has remained almost unexplored.