Second harmonic generation from aluminum plasmonic nanocavities: from scanning to imaging

Area of Science:

• Nanophotonics and Plasmonics
• Materials Science
• Nonlinear Optics

Background:

• Aluminum (Al) metamaterials and plasmonic structures are cost-effective and stable alternatives to rare metals like gold and silver.
• Aluminum's unique dielectric properties enable efficient surface plasmon excitation in the ultraviolet spectrum with low losses.
• Previous research predominantly focused on gold and silver due to challenges in fabricating smooth aluminum thin films.

Purpose of the Study:

• To detect and characterize second harmonic generation (SHG) from triangular hole arrays in thin aluminum films.
• To evaluate the performance, stability, and reproducibility of aluminum nanostructures for nonlinear optical applications.
• To investigate the influence of structural symmetry on directional emission and demonstrate advanced imaging capabilities.

Main Methods:

• Fabrication of triangular hole arrays in thin aluminum films.
• Detection and characterization of second harmonic generation (SHG) in reflection mode at normal incidence.
• Utilizing a nonlinear single-spinning disk microscope for large-field, instantaneous SHG imaging.

Main Results:

• Intense nonlinear responses and year-long stability were observed from the aluminum nanostructures.
• Aluminum structures demonstrated superior performance compared to gold counterparts.
• High reproducibility allowed investigation of symmetry-dependent directional emission; advanced SHG imaging was achieved.

Conclusions:

• Aluminum nanostructures are highly promising for nonlinear optics, offering significant advantages over traditional plasmonic materials.
• The robustness and stability of aluminum enable detailed studies of structure-property relationships and advanced imaging applications.
• High spatio-temporal resolution SHG imaging of aluminum nanostructures has potential applications in studying dynamic processes like electrochemical reactions.