Solid-State High Harmonic Generation in Common Large Bandgap Substrate Materials.

Area of Science:

• Ultrafast spectroscopy
• Quantum materials science
• Solid-state physics

Background:

• Solid-state high harmonic generation (sHHG) spectroscopy is a powerful technique for probing electronic structure and crystal symmetries in materials.
• Substrate-supported samples are commonly used, with the assumption that substrates do not contribute significantly to the sHHG signal.
• This assumption may not hold, as substrates can emit sHHG signals, potentially interfering with the analysis of the target material.

Purpose of the Study:

• To investigate and characterize the sHHG emissions from commonly used optical substrates.
• To evaluate the influence of substrate properties (e.g., crystalline quality, orientation) on sHHG.
• To provide guidance for selecting appropriate substrates to minimize interference in sHHG studies of novel quantum materials.

Main Methods:

• Power-dependent and polarization angle-resolved sHHG measurements were performed.
• Fused silica, calcium fluoride, diamond, and sapphire substrates were studied.
• A mid-infrared (MIR) driving field was used for sHHG excitation.

Main Results:

• Substrate sHHG emissions were observed at moderate driving field intensities.
• The sHHG yield and angular dependence of substrates vary significantly.
• Different crystalline qualities and orientations of the same substrate material exhibit distinct sHHG characteristics.

Conclusions:

• Substrate contributions to sHHG must be carefully considered, especially at higher driving field intensities.
• Optimal substrate selection is crucial for accurate interpretation of sHHG data from novel materials.
• This work facilitates the study of a broader range of materials by minimizing substrate-related artifacts.