Refractive index sensor based on multiple Fano resonances in a plasmonic MIM structure

Area of Science:

• Photonics
• Nanophotonics
• Plasmonics

Background:

• Refractive index sensors are crucial for various applications, including chemical detection and biosensing.
• Existing sensors often face limitations in sensitivity, integration, and size.
• Chip-scale photonic devices offer miniaturization and potential for high-density integration.

Purpose of the Study:

• To propose and analyze a novel chip-scale refractive index sensor.
• To achieve ultra-high sensitivity and a high figure of merit using multiple Fano resonances.
• To explore the potential for integration into advanced photonic circuits.

Main Methods:

• Utilizing a metal-insulator-metal (MIM) structure with coupled semi-ring cavities and a vertical cavity.
• Employing the finite-difference time-domain (FDTD) method for electromagnetic simulation.
• Applying multimode interference coupled-mode theory (MCCT) for spectral analysis.

Main Results:

• Successfully generated up to six ultra-sharp and asymmetrical Fano resonance peaks.
• Achieved an ultra-high refractive index sensitivity of 1405 nm/RIU.
• Obtained a figure of merit (FOM) of 3.62×10^5.

Conclusions:

• The proposed MIM structure effectively supports multiple Fano resonances for sensing.
• The demonstrated high sensitivity and FOM make it suitable for advanced refractive index sensing.
• This chip-scale sensor holds promise for integration into highly advanced photonic circuits.