Plasmonic bound states in the continuum to tailor light-matter coupling

Area of Science:

• Nanophotonics
• Metasurfaces
• Plasmonics

Background:

• Plasmon resonances are crucial for light-matter interactions but suffer from low quality factors, limiting spectral selectivity.
• Existing plasmonic nanostructures often lack the necessary quality factors for demanding applications.

Purpose of the Study:

• To design and fabricate plasmonic nanofin metasurfaces with high-quality factor modes.
• To demonstrate the tunability of these modes through symmetry breaking for enhanced light-matter interactions.
• To explore the application of these metasurfaces in pixelated molecular sensing.

Main Methods:

• 3D laser nanoprinting of plasmonic nanofin metasurfaces.
• Investigating symmetry-protected bound states in the continuum (BICs).
• Engineering out-of-plane symmetry breaking via nanofin triangle angle adjustment.

Main Results:

• Achieved high-quality factor (up to 180) modes under normal incidence by breaking out-of-plane symmetry.
• Demonstrated precise control over radiative and intrinsic losses by tuning the triangle angle.
• Successfully accessed under-, critical, and over-coupled regimes for enhanced molecular sensing.
• Observed a strong dependence of sensing performance on the coupling regime.

Conclusions:

• Plasmonic nanofin metasurfaces offer a versatile platform for tailored light-matter interactions.
• Symmetry breaking is a key strategy to achieve high-quality factor plasmonic modes.
• The developed metasurfaces show significant potential for sensitive and selective molecular sensing.