Tunable triple Fano resonances based on multimode interference in coupled plasmonic resonator system

Area of Science:

• Plasmonics
• Nanophotonics
• Optical metamaterials

Background:

• Fano resonances in plasmonic structures offer sharp spectral features.
• Coupled plasmonic resonator systems exhibit complex resonance phenomena.
• Existing theories may not fully capture multi-mechanism Fano resonances.

Purpose of the Study:

• To design and analyze an asymmetric plasmonic structure supporting triple Fano resonances.
• To develop a theoretical framework for understanding multi-mechanism Fano resonances.
• To demonstrate the independent tunability of these resonances for device applications.

Main Methods:

• Fabrication of an asymmetric plasmonic structure with metal-insulator-metal (MIM) waveguides and rectangular cavities.
• Theoretical modeling using multimode interference coupled mode theory (MICMT) based on coupled mode theory (CMT).
• Numerical simulations to analyze Fano resonance characteristics and tunability.

Main Results:

• The proposed structure supports triple Fano resonances arising from distinct physical mechanisms.
• MICMT accurately describes the multi-mechanism Fano resonance phenomenon.
• Each Fano resonance can be independently tuned by adjusting cavity parameters.
• Achieved narrow 'M'-type double Lorentzian-like transmission windows with tunable position and FWHM.

Conclusions:

• The asymmetric plasmonic structure effectively generates and controls triple Fano resonances.
• The MICMT provides a robust theoretical foundation for coupled plasmonic systems.
• The tunable transmission windows have significant potential for advanced optical devices.