Characterization of nanostructured plasmonic surfaces with second harmonic generation.

Area of Science:

• Nonlinear Optics
• Nanophotonics
• Surface Science

Background:

• Second harmonic generation (SHG) is sensitive to surface and interface properties.
• Nanostructured metal surfaces exhibit high surface-to-volume ratios and near-field enhancements ('hot spots').
• Hot spots arise from nanoscale geometric features or surface plasmon resonances, significantly impacting nano-optics.

Purpose of the Study:

• To investigate the influence of near-field hot spots on the second harmonic generation (SHG) response of nanostructured metal surfaces.
• To analyze these influences on both microscopic and macroscopic levels.

Main Methods:

• Microscopic characterization using scanning SHG microscopy.
• Rigorous numerical simulations of near-field and local electric currents.
• Macroscopic characterization via SHG-circular dichroism and magnetization-induced SHG.

Main Results:

• Demonstrated the significant role of hot spots in enhancing SHG signals from nanostructured metals.
• Provided insights into the microscopic origins and macroscopic manifestations of hot spot effects.
• Correlated nanoscale features and plasmonic behavior with SHG output.

Conclusions:

• Near-field hot spots are crucial for understanding and optimizing SHG signals in nanostructured metal systems.
• The combined microscopic and macroscopic approaches offer a comprehensive view of SHG phenomena.
• This work advances the application of SHG for probing nanoscale optical properties.