Dual-band complementary metamaterial perfect absorber for multispectral molecular sensing

Area of Science:

• Plasmonics and Nanophotonics
• Metamaterial Perfect Absorbers (MPAs)
• Surface-Enhanced Infrared Absorption (SEIRA) Spectroscopy

Background:

• Metamaterial perfect absorbers (MPAs) are crucial for advanced sensing applications.
• Enhanced absorption requires localized hotspots accessible to analytes.
• Surface-enhanced infrared absorption (SEIRA) spectroscopy benefits from strong mode confinement.

Purpose of the Study:

• To propose a quasi-three-dimensional MPA for sensitive refractive index and molecular vibrational sensing.
• To design an MPA with exposed and confined hotspots for enhanced absorption.
• To enable dual-band perfect absorption for simultaneous detection.

Main Methods:

• Fabrication of a quasi-three-dimensional MPA using cross-shaped coupled complementary plasmonic arrays.
• Analysis of plasmonic resonances: electric dipole-like and magnetic dipole-like modes.
• Investigation of the MPA's response to ultrathin polymethyl methacrylate (PMMA) films.
• Simultaneous detection of molecular vibrations (C=O and C-H) by adjusting cross branch lengths.

Main Results:

• Achieved dual-band perfect absorption through coupled plasmonic resonances.
• Demonstrated high sensitivity to refractive index changes (11.8 nm/nm shift for PMMA).
• Enabled simultaneous detection of C=O and C-H vibrations.
• Observed mode splitting and anti-crossing, indicating strong plasmon-molecule interaction.

Conclusions:

• The proposed dual-band MPA offers exceptional sensitivity for refractive index sensing.
• The MPA facilitates multispectral molecular vibrational sensing with high accuracy.
• This work opens new possibilities for developing highly sensitive plasmonic sensors.