Tunable multi-band terahertz sensor based on graphene plasmonic metasurfaces

Area of Science:

• Plasmonics
• Metasurfaces
• Terahertz (THz) Sensing

Background:

• Conventional plasmonic sensors often exhibit limited sensitivity or sensing bands.
• Terahertz technology offers unique properties for label-free biosensing and material characterization.
• Graphene integration in metasurfaces provides tunable electronic and optical properties.

Purpose of the Study:

• To introduce a novel metal-dielectric-dielectric-metal (MDDM) metasurface architecture for enhanced refractive index sensing in the THz region.
• To demonstrate triple-band sensing capabilities with high sensitivity using a graphene-based fractal pattern.
• To investigate the underlying plasmonic resonance mechanisms and their impact on sensor performance.

Main Methods:

• Fabrication of a multilayer MDDM structure comprising graphene, dielectric layers, silicon substrate, and aluminum.
• Utilizing strong plasmonic resonances and enhanced absorption within the metasurface.
• Analyzing the spectral response across three distinct resonance modes (dipolar, quadrupolar, hybridized) for refractive index sensing.

Main Results:

• Achieved high sensitivities of 10 μm/RIU, 3 μm/RIU, and 2.75 μm/RIU across three distinct sensing modes.
• Demonstrated triple-band sensing capability, surpassing single- and dual-band sensors.
• Observed enhanced field localization and intense electromagnetic "hot spots" due to dual-dielectric configuration and hybridized resonances.

Conclusions:

• The proposed MDDM sensor exhibits superior sensitivity and flexibility for refractive index sensing in the THz range.
• The tunable nature and stable performance under environmental variations highlight its practical potential.
• Significant promise for applications in label-free biomedical diagnostics, gas sensing, and glucose monitoring.