Self-Assembly of Plasmonic Nanoantenna-Waveguide Structures for Subdiffractional Chiral Sensing

Area of Science:

• Plasmonics and Nanophotonics
• Chiral Optics
• Nanoscale Sensing

Background:

• Spin-momentum locking links electromagnetic field spin to propagation direction.
• This effect can be used to probe the circular dichroism of chiral objects.
• Existing methods often lack sub-diffraction limited resolution.

Purpose of the Study:

• To demonstrate local, sub-diffraction limited chiral coupling using a gold nanoantenna and silver nanowire system.
• To develop a sensor for probing circular dichroism with high sensitivity.
• To explore on-chip sensing capabilities for chiral analytes.

Main Methods:

• Fabrication of a self-assembled gold nanoantenna and silver nanowire system with a silica shell.
• Characterization using correlated electron microscopy, energy-dispersive X-ray spectroscopy, dark-field, and fluorescence imaging.
• 3D numerical simulations to support experimental findings.

Main Results:

• Achieved local, sub-diffraction limited chiral coupling between light and surface plasmon polaritons.
• Demonstrated a sensitivity of 1 mdeg for light field ellipticity.
• Derived a circular dichroism sensitivity of 10^3 deg cm^2/dmol for local analytes.

Conclusions:

• The nanoantenna-nanowire system acts as an effective sensor for chiral response.
• The sensor operates far below the diffraction limit, offering ultracompact chiral detection.
• Prototypical design modeling predicts successful on-chip sensing of chiral analytes.