Data from: Solid-state high harmonic generation in common large bandgap substrate materials

Solid-state high harmonic generation (sHHG) spectroscopy is an emerging
ultrafast technique for studying key material properties such as
electronic structure at and away from equilibrium. sHHG anisotropy
measurements, where sHHG spectra are recorded depending on the driving
electric field relative to the crystal lattice, have become a powerful
tool for studying crystal symmetries. Previous works on two-dimensional
materials and other quantum materials have often used substrate-supported
samples, assuming that all sHHG signals originate from the sample due to
the relatively large bandgap of the substrate. While this assumption is
generally reasonable, we show that some sHHG emissions from commonly used
substrates can occur at moderate intensities of the sHHG driving field. In
addition, we show that it is essential to consider not only the sHHG yield
from a substrate but also its angular dependence relative to the material
of interest. Specifically, in this work, the power-dependent and
polarization angle-resolved sHHG emissions of fused silica, calcium
fluoride, diamond, and sapphire of two different crystalline qualities and
orientations are compared using a mid-infrared (MIR) driving field. This
empirical characterization aims to guide the substrate selection for sHHG
studies of novel materials to minimize the misattribution and interference
of substrate-related sHHG emissions, which opens the possibility to study
a wider array of materials.