Abstract
Electromagnetic (EM) wave absorption plays a vital role in photonics. While metasurfaces are proposed to absorb EM waves efficiently, most of them exhibit limited bandwidth and fixed functionalities. Here, we propose a broadband and tunable terahertz (THz) absorber based on a graphene-based metasurface, which is constructed by a single layer of closely patterned graphene concentric double rings and a metallic mirror separated by an ultrathin SiO2 layer. Plasmonic hybridization between two graphene rings significantly enlarges the absorption bandwidth, which can be further tuned by gating the graphene. Moreover, the specific design also makes our device insensitive to the incident angle and polarization state of impinging EM waves. Our results may inspire certain wave-modulation-related applications, such as THz imaging, smart absorber, tunable sensor, etc.
Highlights
Perfect electromagnetic (EM) absorbers have drawn considerable interests in photonic research due to many potential applications, such as solar photovoltaics cells, heat radiations, photo-detections [1,2]
A class of reflection-type metasurfaces, typically consisting of metal-insulator-metal sandwiched structures, were widely adopted to achieve perfect EM-wave absorption, utilizing the magnetic resonance between the top and bottom metallic layers [10,11]. These ideas inspire a series of works on EM wave absorptions ranging from microwave, THz to optical frequency [12,13,14,15]
2.1 Geometry and principle of the proposed graphene absorber Figure 1 depicts the schematic of the proposed graphene-based metamaterial-based prefect absorber (MPA), which is constructed by a single layer of the graphene concentric double ring (GCDR) array and an optically thick gold mirror, separated by a 28μm-thick lossless SiO2 spacer with εd =3.9
Summary
Perfect electromagnetic (EM) absorbers have drawn considerable interests in photonic research due to many potential applications, such as solar photovoltaics cells, heat radiations, photo-detections [1,2]. A class of reflection-type metasurfaces, typically consisting of metal-insulator-metal sandwiched structures, were widely adopted to achieve perfect EM-wave absorption, utilizing the magnetic resonance between the top and bottom metallic layers [10,11]. These ideas inspire a series of works on EM wave absorptions ranging from microwave, THz to optical frequency [12,13,14,15]. Our results may point out a new possibility to achieve broadband tunable metadevices in THz and other frequency domains
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