Abstract
Graphene-based devices have important applications attributed to their superior performance and flexible tunability in practice. In this paper, a new kind of absorber with monolayer graphene sandwiched between two layers of dielectric rings is proposed. Two peaks with almost complete absorption are realized. The mechanism is that the double-layer dielectric rings added to both sides of the graphene layer are equivalent to resonators, whose double-side coupled-cavity effect can make the incident electromagnetic wave highly localized in the upper and lower surfaces of graphene layer simultaneously, leading to significant enhancement in the absorption of graphene. Furthermore, the influence of geometrical parameters on absorption performance is investigated in detail. Also, the device can be actively manipulated after fabrication through varying the chemical potential of graphene. As a result, the frequency shifts of the two absorption peaks can reach as large as 2.82 THz/eV and 3.83 THz/eV, respectively. Such a device could be used as tunable absorbers and other functional devices, such as multichannel filters, chemical/biochemical modulators and sensors.
Highlights
Different from some research in which only single-side coupled-cavity structures have been investigated [27,28,29], the double-layer dielectric rings we proposed to add to both sides of monolayer graphene could be more efficient to enhance the electric-field intensities on the upper and lower surfaces of graphene, whose double-side coupled-cavity effect could increase the absorption of graphene
On an insulator substrate with refractive index nsub = 1.45, monolayer graphene is sandwiched between two layers of identical dielectric-ring arrays
We introduce a new kind of high-quality graphene-based absorber using a double-side coupled-cavity effect
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Periodic multi-layer dielectric materials have been reported to enhance the absorption of graphene based on optical resonance effect [22,23,24,25,26] These achievements open up a new way for designing graphene-based absorbers. In these approaches, no matter if adding periodic metal units or multi-layer dielectric materials to monolayer graphene, it needs a complicated fabrication process or it may give rise to a big size of device. In these studies, only single-side coupled-cavity effect has been applied. The use of dielectric rings shows advantages in terms of fabrication cost since they have a lower price
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