A Broadband Tunable Terahertz Metamaterial Absorber Based on Single-Layer Complementary Gammadion-Shaped Graphene

Area of Science:

• Optics and Photonics
• Materials Science
• Condensed Matter Physics

Background:

• Metamaterial absorbers (MMAs) are crucial for controlling electromagnetic waves.
• Tunable absorption in the terahertz (THz) spectrum is highly desirable for advanced applications.
• Graphene's unique electronic properties offer a pathway for dynamic control of optical responses.

Purpose of the Study:

• To design and demonstrate a simple, broadband, and electrically tunable metamaterial absorber in the THz region.
• To investigate the tunability mechanism based on graphene's Fermi energy modulation.
• To explore potential applications in filtering, modulation, and sensing.

Main Methods:

• Fabrication of a single-layer complementary gammadion-shaped (CGS) graphene sheet on a polydimethylsiloxane (PDMS) substrate and a metal film.
• Electrical tuning of graphene's Fermi energy (E) using a DC bias voltage.
• Numerical simulations to analyze absorption spectra, electric field distributions, and polarization/angle dependence.

Main Results:

• Achieved broadband absorption (>90%) with a maximal relative bandwidth of 72.1% at E = 0.8 eV.
• Demonstrated electrical tunability of absorbance from 42% to 99.1% by varying E from 0 eV to 0.8 eV.
• Confirmed broadband absorption originates from surface plasmon polaritons (SPPs) on the CGS graphene, with polarization-insensitive and wide-angle characteristics.

Conclusions:

• The proposed simple MMA design offers effective broadband absorption and flexible electrical tunability in the THz range.
• The dynamic control of absorption via graphene's Fermi energy level opens possibilities for advanced THz devices.
• The MMA shows significant potential for applications in tunable filtering, modulators, and sensing.