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

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.

This work theoretically proposes a broadband light modulator based on a graphene-hybrid metasurface. The tunability is achieved by adjusting graphene Fermi energy after its electroabsorption has been enhanced, and the broadband modulation is realized with the arrangement of four silver blocks in one cell to support multiple resonance modes. Besides, the mechanism of this broadband enhancement is analyzed from the electric and magnetic field distribution characteristics. The tunability can be realized at any wavelength in the whole range by tuning the bias voltage. Moreover, the modulation depth and ON/OFF status switchability have been presented to show its dynamical manipulations.

This indicates that adjusting the diameter can effectively tune the entire spectrum to a desired wavelength range.  demonstrates that, as the parameter m increases gradually, the spectrum initially undergoes a rapid blue-shift and then stabilizes. Simultaneously, there is a slight decrease in the maximum absorption. It is worth noting that during the fabrication process, a large block height can lead to instability, making a smaller value of m more preferable.

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