Self-Reference Refractive Index Sensor Based on Independently Controlled Double Resonances in Side-Coupled U-Shaped...

Area of Science:

• Photonics and Nanotechnology
• Optical Sensing
• Plasmonics

Background:

• Metal-dielectric-metal (MDM) waveguides are crucial for plasmonic devices.
• U-shaped cavities offer unique optical properties for sensor design.
• Achieving high sensitivity and self-referencing in nanosensors is a key challenge.

Purpose of the Study:

• To theoretically and numerically investigate a novel plasmonic refractive index nanosensor.
• To explore the phenomenon of a transparency window in coupled U-shaped cavities.
• To demonstrate self-reference sensing capabilities based on differential resonance shifts.

Main Methods:

• Theoretical analysis and numerical simulations of a plasmonic nanosensor.
• Design of two U-shaped cavities side-coupled to an MDM waveguide.
• Mapping magnetic field distribution to understand optical phenomena.

Main Results:

• Observation of a transparency window between two transmission dips.
• Realization of independent double resonances with diverse responses to structural variations.
• One resonance showed significant shift with refractive index change, while the other remained stable.
• Achieved high sensitivity (917 nm/RIU) and figure of merit (180 RIU⁻¹).

Conclusions:

• The proposed nanosensor design enables high-sensitivity optical sensing.
• Differential resonance behavior facilitates self-reference sensing for improved accuracy.
• This work aids in developing on-chip optical sensors for complex environments.