Dynamic tunable and switchable broadband near-infrared absorption modulator based on graphene-hybrid metasurface

Abstract

The integration of graphene with metasurfaces enables devices with remarkable dynamic tunability, propelling electromagnetic (EM) manipulations to new heights by transitioning from static to dynamic control. In this study, we theoretically investigate a broadband absorption modulator with dynamic tunability based on a graphene hybrid metasurface. The metasurface consists of a monolayer graphene sheet sandwiched between a square silver block and a silica layer. The excitation of the magnetic toroidal dipole (MTD) leads to a significant enhancement of graphene’s electromagnetic absorption. By arranging four blocks as a supercell to support multi-resonance, we achieve a broadband modulator spanning from 1000 to 1210 nm, with graphene absorption exceeding 57 %. Notably, there is no plasmonic hybridization among adjacent components within the super unit. By tuning the Fermi energy of graphene, narrow-band tunability can be achieved at any wavelength within the operation spectrum. Furthermore, the designed device exhibits a perfect modulation depth (∼100 %). We demonstrate the switchability of the proposed device by showcasing its ON/OFF status at representative wavelengths of 1205 nm, 1119 nm, and 1052 nm. Thus, the proposed graphene-based hybrid metasurface fulfills the requirements for broadband tunability and switchability, offering a high ON/OFF ratio, full modulation depth, and a small switch voltage gap. This design holds significant potential for future developments.