Terahertz dynamic multiband perfect absorber with a digital coding graphene-diamond metasurface

The monolayer graphene-based terahertz (THz) perfect absorber has made significant progress in switchable devices with diverse functionalities. However, existing methods for achieving switchability rely on either multilayered metasurface with complex configurations or complicated patterned metasurfaces. A switchable absorber that switches between n-band and m-band modes (n, m correspond to the number of resonance peaks) using tunable materials is also interesting but has not yet been mentioned. Here, a dynamically switchable multiband perfect absorber with a digital coding graphene metasurface is proposed and demonstrated. By integrating multiple metasurface units with different Fermi levels into a newly generated period, we realize a multiband perfect absorber with a rather simple and straightforward configuration composed of a patterned metasurface. Through introducing a digital coding metasurface into the perfect absorber, we use the digital signals via FPGA (field programmable gate array) to convert n-band into m-band absorption modes. Moreover, the results reveal that the THz perfect absorber, possessing great impedance matching with the free space, has excellent angle tolerance and robustness. Such a perfect absorber offers a flexible tool for selecting THz channels and may pave the way for sixth-generation communication.