Graphene terahertz absorber and graded plasma metamaterials

Optical metamaterials are an effective way to utilize their superior photon capture capabilities. Therefore, perfect absorbers can be achieved through nanoscale resonant plasmas and metamaterial structures.

Metamaterial perfect absorbers (MPAs) are typically composed of periodic subwavelength metals (such as plasma superabsorbers) or dielectric resonance units. Compared with static passive physical systems, tunable metamaterials can dynamically manipulate electromagnetic waves and improve multidimensional control of optical response. There are two typical strategies for achieving tunable properties in metamaterials: mechanical reconstruction and altering the lattice structure of metamaterials.

Compared to these classical methods, the combination of functional materials and metamaterial structures provides a way to change the optical properties of materials through external stimuli and has a faster response rate. Graphene, as a typical tunable functional material, has excellent mechanical, electrical, and optical properties. Combining graphene into metamaterial structures can significantly enhance the interaction between light and matter.

In this regard, Professor Wu Weiping's team has demonstrated a novel tunable ultra wideband terahertz absorber by utilizing the unique characteristics of graphene and hierarchical structure plasma metamaterials. The research paper of the team was published in the journal Advanced Equipment and Instruments.

The metamaterial structure includes alternating T-shaped gold bars/squares, dielectric layers, and graphene layers on the gold layer. The average absorption of MPA achieved 90% in the ultra wide frequency range from 20.8 THz to 39.7 THz. The origin of broadband characteristics was analyzed through electric field diagrams, and the modulation of graphene on the absorption window was studied. In addition, the influence of different parameters on the results was studied, and the potential applications of this structure in the field of optoelectronics were discussed.

Finally, some broadband absorbers in the terahertz far infrared band recently reported were compared and analyzed with the results of this work. The proposed metamaterial broadband absorber has higher average absorption and a wider frequency range. The proposed structure only has a patterned layer of gold, which has significant advantages in manufacturing compared to other literature.

In summary, a novel ultra wideband tunable terahertz absorber for graphene and hierarchical structure plasma metamaterials was proposed and studied, and numerical studies were conducted on the almost perfect ultra wideband absorption of 20.8THz-39.7THz. The proposed absorber is achieved by alternately arranging two gold structures of different sizes in each crystal cell. The bandwidth absorbed by the broadband absorber exceeds 90% and is approximately 18.9 THz.

By adjusting the Fermi level of graphene, the position of ultra wideband can be adjusted. In addition, the influence of geometric parameters on the absorption spectrum of the absorber was quantitatively analyzed. These results indicate that the metamaterial absorber proposed in this work can bring further improvements in the fields of tunable filtering, detectors, controlled thermal radiation, and other photonic devices.

Source: Laser Net