Multimode Fano Resonances Sensing Based on a Non-Through MIM Waveguide with a Square Split-Ring Resonance Cavity

Area of Science:

• Photonics
• Plasmonics
• Nanotechnology

Background:

• Fano resonances offer sharp spectral features crucial for sensing.
• Metal-insulator-metal (MIM) waveguides are fundamental components in plasmonic devices.
• Square split-ring resonators (SSRCs) can be used to engineer optical responses.

Purpose of the Study:

• To design and analyze a non-through MIM waveguide exhibiting fivefold Fano resonances.
• To investigate the tunability of Fano resonance characteristics via geometric parameters.
• To evaluate the potential of the proposed structure for optical refractive index sensing and biosensing.

Main Methods:

• Utilized the finite element method (FEM) for detailed electromagnetic simulations.
• Analyzed transmission characteristics and magnetic field distributions.
• Optimized geometric parameters of the SSRC and MIM waveguide.

Main Results:

• Achieved fivefold Fano resonances through the interaction of SSRC modes and the bus waveguide.
• Demonstrated independent tuning of Fano resonance wavelength and transmittance by adjusting SSRC geometry.
• Obtained optimal refractive index sensing sensitivity (S) of 1290.2 nm/RIU and figure of merit (FOM) of 3.6 × 10^4.
• Showcased the potential for biosensing by filling the annular cavity with biomass solution.

Conclusions:

• The proposed non-through MIM waveguide effectively generates multiple Fano resonances.
• Independent control over resonance properties is achievable through geometric optimization.
• The structure exhibits high performance for optical refractive index sensing and holds promise for biosensing applications in micro and nano fields.