Fano resonances based on multimode and degenerate mode interference in plasmonic resonator system

Area of Science:

• Plasmonics
• Nanophotonics
• Optical Resonators

Background:

• Fano resonances arise from interference between resonant and continuum states.
• Plasmonic resonator systems offer unique optical properties for light manipulation.
• Understanding Fano resonance mechanisms is crucial for advanced optical device design.

Purpose of the Study:

• To investigate three distinct Fano resonance mechanisms in a coupled circular plasmonic resonator system.
• To develop theoretical models for explaining these Fano resonances.
• To evaluate the potential of these resonances for sensing and optical applications.

Main Methods:

• Theoretical investigation using multimode interference coupled mode theory (MICMT).
• Numerical simulations of the plasmonic resonator system.
• Development of degenerate interference coupled mode theory (DICMT) for symmetry-broken systems.

Main Results:

• Identified three types of Fano resonances based on different physical mechanisms: intra-cavity mode interference, inter-cavity mode interference, and degenerate interference.
• MICMT and DICMT successfully explain the observed Fano resonances.
• Achieved high sensitivity (840 nm/RIU) and figure of merit (FOM* = 100).

Conclusions:

• The study provides a comprehensive understanding of Fano resonances in coupled plasmonic resonators.
• The proposed theoretical frameworks (MICMT and DICMT) are effective for analyzing these phenomena.
• The demonstrated high performance indicates significant potential for applications in refractive index sensors, optical splitters, and slow-light devices.