A tri-functional, independently tunable terahertz absorber based on a vanadium dioxide–graphene hybrid structure

Abstract

This paper proposes a simulated design for a versatile terahertz absorber that can be actively tuned. The absorber utilizes the unique tuning capabilities of graphene and vanadium dioxide, enabling it to alternate between ultra-broadband absorption, broadband absorption, and almost complete reflection. In the metallic phase of vanadium dioxide, coupled with a graphene Fermi level at 0 eV, the absorber achieves ultra-broadband absorption. This spans an extensive frequency range from 3.85 THz to 9.73 THz, exhibiting an absorption rate surpassing 90%. As we shift to the insulating phase of vanadium dioxide and adjust the graphene Fermi level to 1 eV, the absorber operates in a broadband absorption mode. This mode spans 2.98 THz to 4.63 THz, demonstrating an absorption rate exceeding 90%. In the insulating state of vanadium dioxide with a graphene Fermi level at 0 eV, the absorber metamorphoses into a nearly total reflector. Its maximum absorption rate is a mere 0.52%. The unique adjustability of vanadium dioxide and graphene independently enables the fine-tuning of absorption rates for both ultra-broadband and broadband absorption without encountering interference. Additionally, thanks to the central symmetry inherent in the proposed structure, the absorber exhibits insensitivity to alterations in polarization angles and remains stable under a broad range of incident angles. With these benefits, the absorber shows promising potential for applications in electromagnetic stealth, wireless communication, and so on.