Mie resonance induced broadband near-perfect absorption in nonstructured graphene loaded with periodical dielectric wires

Abstract

In general, there is a fundamental trade-off between the operational bandwidth and the attainable absorption. So, obtaining broadband wave absorption of a low reference standard such as 90% is not very difficult. However, when trying to obtain higher absorption such as 99%, the bandwidth will drop dramatically. Here, we demonstrate that broadband near-perfect absorption of over 99% absorption with a 60% relative bandwidth can be obtained utilizing single-layered and nonstructured graphene loaded with periodical dielectric wires. The absorption mechanism originates from the coupling of Mie resonances in dielectric wires excited by the incident wave to the graphene plasmon resonances, which introduces two absorption contributions: direct near-field absorption in the graphene and radiative emission into the graphene.

Graphene-Based Perfect Absorption Structures in the Visible to Terahertz Band and Their Optoelectronics Applications

“…The broadband absorption structures discussed above are based on patterned graphene which will result in some edge effects, thus rendering it difficult to realize perfect absorption in reality. In order to avoid the edge effects, broadband perfect absorption structures based on unpatterned graphene are put forward [24,118,119]. In 2017, F. Gao et al demonstrated a broadband perfect absorption structure by using single-layered unpatterned graphene [118].…”

“…The structure supports three graphene plasmon resonances, which cause three absorption peaks (denoted as A, B and C) in the absorption spectrum. In 2018, J. Yang et al proposed a broadband perfect absorption structure with a flat-top absorption spectrum by coupling monolayer unpatterned graphene with periodical dielectric wires [24]. The schematic image of the proposed structure is shown in Figure 4c, which consists of monolayer graphene sandwiched between periodical dielectric wires and a dielectric substrate on top of a metallic film.…”

“…( c ) Schematic illustration of the absorption structure by coupling unpatterned graphene with dielectric wires. ( d ) Calculated absorption spectrum of the designed structure shown in ( c ) for TM polarization under normal incidence [24]. Reproduced from references [24,118], with permission from Optical Society of America, 2018; with permission from Optical Society of America, 2017.…”

“…In the mid-infrared (IR) to terahertz (THz) band, graphene supports plasmon resonances, which can greatly enhance the near-field of graphene. Thus, many perfect absorption structures based on graphene plasmons have been proposed, such as narrowband perfect absorption structure in the mid-IR [18], dual-band perfect absorption structures in the THz [19,20], multi-band perfect absorption structures in the mid-IR [21,22], broadband perfect absorption structures in the THz [23,24], and coherent perfect absorption structures in the mid-IR and THz [25,26]. Meanwhile, without exciting the graphene plasmons, some graphene-based perfect absorption structures were also demonstrated by using the impedance matching concept [27] or special designs [28,29,30] in the THz band, and by using the big incident angle in the mid-IR band [31].…”

A Broadband Tunable Terahertz Metamaterial Absorber Based on Single-Layer Complementary Gammadion-Shaped Graphene

“…However, most of these MMAs are usually narrowband, which greatly limits their applications in some circumstances. Numerous efforts have been made to realize multi-and broadband absorption by various methods, including multilayer graphene structures [32], multiple graphene resonators in a unit cell [33], structured graphene with gradually changing geometric sizes [34], and other hybrid-patterned metal-graphene composite structures [33][34][35][36][37]. Although the broad absorption bandwidth of the MMAs can be enhanced, most of them still suffer from some drawbacks, including difficulty with absorption tuning via biasing, significant polarization and incident angle dependence, and complicated fabrication technology.…”