An Electrically Tunable Dual-Wavelength Refractive Index Sensor Based on a Metagrating Structure Integrating...

Area of Science:

• Optoelectronics
• Nanophotonics
• Biosensing

Background:

• Metal-insulator-metal (MIM) structures are crucial for plasmonic devices.
• Indium tin oxide (ITO) exhibits epsilon-near-zero (ENZ) properties tunable with voltage.
• Developing sensitive and reconfigurable biosensors is vital for medical diagnostics.

Purpose of the Study:

• To propose and numerically investigate a reconfigurable sensing platform based on an asymmetrical MIM structure.
• To demonstrate near-perfect absorption via ENZ and antisymmetric modes.
• To evaluate the device's performance as a highly sensitive biosensor for glucose solutions.

Main Methods:

• Numerical investigation of an asymmetrical metal-insulator-metal stacked structure with an ITO ultrathin film.
• Excitation of epsilon-near-zero (ENZ) and antisymmetric modes.
• Analysis of absorptivity modulation by varying ITO's ENZ wavelength with applied voltage.

Main Results:

• Achieved near-perfect absorption (>99.7%) at 1144 nm (ENZ mode) and 1404 nm (antisymmetric mode).
• Modulated ENZ mode absorptivity from 90.2% to 98.0% using voltage control.
• Demonstrated high sensitivity (213.3 nm/RI) and figure-of-merit (FOM=24.7) for glucose detection.

Conclusions:

• The proposed structure enables tunable absorption through voltage-controlled ENZ properties.
• The device exhibits excellent performance metrics for biosensing applications.
• This reconfigurable platform holds potential for developing advanced, real-time health monitoring biosensors.