Improved Refractive Index-Sensing Performance of Multimode Fano-Resonance-Based Metal-Insulator-Metal Nanostructures

Area of Science:

• Plasmonics
• Nanophotonics
• Optical Sensing

Background:

• Refractive index sensors are crucial for detecting various materials.
• Metal-insulator-metal (MIM) waveguide structures offer unique plasmonic properties.
• Fano resonance in plasmonic structures enables high-sensitivity sensing.

Purpose of the Study:

• To propose and investigate a novel multiple mode Fano resonance-based refractive index sensor.
• To enhance sensor sensitivity and light-matter interaction through structural modifications.
• To demonstrate the sensor's capability for detecting a wide range of substances.

Main Methods:

• Utilizing the finite element method for systematic study of sensor structures.
• Designing a metal-insulator-metal (MIM) waveguide with specific resonators and defects.
• Analyzing the effect of structural parameters (air stubs, air path, metal defects) on sensor performance.

Main Results:

• Surface plasmon mode splitting is sensitive to sensor geometry.
• Dual air stubs and an embedded air path enhance cavity plasmon resonance.
• Metal defects in the bus waveguide facilitate gap plasmon resonance.
• Achieved high sensitivities of 2600 nm/RIU (mode 1) and 1200 nm/RIU (mode 2).
• Demonstrated significant sensitivity enhancement compared to conventional structures.

Conclusions:

• The proposed Fano resonance sensor exhibits remarkable sensing characteristics.
• The structural design effectively enhances light-matter interaction and sensitivity.
• The sensor is suitable for detecting refractive indices of gases, liquids, and biomaterials.