Plasmonic nanosensor based on Fano resonance in waveguide-coupled resonators

Area of Science:

• Plasmonics
• Nanophotonics
• Optical Sensing

Background:

• Plasmonic nanosensors offer high sensitivity for detecting refractive index changes.
• Fano resonance, arising from coherent interference, provides sharp spectral features crucial for sensing.
• Metal-dielectric-metal waveguides enable strong light confinement for enhanced plasmonic effects.

Purpose of the Study:

• To propose and investigate a novel plasmonic nanosensor based on Fano resonance.
• To demonstrate the sensor's capability for highly efficient refractive index sensing.
• To analyze the dependence of Fano resonance on physical parameters for sensor optimization.

Main Methods:

• Designing a metal-dielectric-metal waveguide side-coupled with nanoresonators.
• Utilizing the coherent interference between discrete and quasi-continuum modes to generate Fano resonance.
• Analyzing the reflection spectrum to identify the Fano dip and its sensitivity to refractive index variations.

Main Results:

• The proposed nanosensor exhibits a sharp asymmetric Fano resonance dip in its reflection spectrum.
• The Fano resonance is sensitive to the cavity-cavity phase and the dielectric's refractive index.
• The sensor achieves a high sensitivity of approximately 900 nm/RIU and a figure of merit of around 500.

Conclusions:

• The plasmonic nanosensor based on Fano resonance is highly efficient for refractive index sensing.
• The achieved sensitivity and figure of merit surpass those of plasmonic sensors utilizing perfect absorbers.
• This design offers a promising platform for advanced optical sensing applications.