Broadband Polarization‐Insensitive Coherent Rasorber in Terahertz Metamaterial with Enhanced Anapole Response and Coupled Toroidal Dipole Modes

Abstract

magnetic energy absorption in the microwave, THz, visible light, and infrared bands. [3][4][5][6][7] Furthermore, the MMAs with dynamically tunable absorption peaks and the operating band have been proposed in recent years depending on the tunable absorbing materials, e.g., graphene, [8] crystals, [9] vanadium dioxide, [10] etc. However, the high absorption in the entire operation band also traps the electromagnetic wave, thus immensely preventing the equipment from communicating with other systems. Thereby, the MMA with an additional transmission window also called metamaterial rasorber (MMR) is designed to solve the problem. The MMRs possessing the wide absorption and narrow transmission window combine the stealth technology and communication, then classified into four categories according to the relative position of the absorption and transmission bands: the absorption-transmission (AT), [11,12] the transmission-absorption (TA), [13,14] the absorption-transmission-absorption (ATA), [15,16] and the dual-absorptiontransmission (DAT) MMRs. [17] However, the conventional design strategies for MMR proposed before mainly focus on the microwave band, but rare in the THz band, thus greatly restricting further application in the future. The application of THz radiation ranging from 1 to 10 THz is paving a new era depending on its superior characteristics, oriented toward the post-5G communication possessing the higher and faster data rate, [18][19][20] high-resolution imaging, [21,22] biochemical sensors, [23,24] activecontrol devices, [25] and other optical activities, [26] which are based on the highly coherent and nonionizing properties of THz radiation, wide unassigned frequency region, and distinctive wavelengths. Comparing to conventional design strategies depending on the electric/magnetic resonances for MMR, the electromagnetic characteristics of multipoles in the THz band supply a promising pathway of tailoring the THz MMR combing the higher-data-rate communication and better electromagnetic shielding.Since the concept of toroidal dipole moment was first proposed by Zel'dovich in 1957, [27] effectively enriching the theoretical framework of the multipole expansion, [28] the toroidal electrodynamics had been blossomed and obtained a substantial Enhanced anapole and coupled toroidal dipole moments sustaining the synthesized terahertz (THz) metamaterial innovatively promise for absorptiontransmission-absorption (ATA) metamaterial rasorber (MMR). The anapole mode, due to the strong interaction of electric and magnetic dipole moments, and Fabry-Pérot resonance are supported by the dumbbell-shaped apertures topologically distributed in a double-layer silver plate, thus forming the transmission window with high frequency-selectivity. Meanwhile, the coupled toroidal dipole moments depending on the toroidal structure can cause destructive and constructive interference in far and near fields, respectively, thus causing much electromagnetic energy loss in a wide band. Combining anapole with toroidal dipole moments, the A...

Low-Loss Dual-Band Transparency Metamaterial with Toroidal Dipole

“…This is the first time that the toroidal dipole was experimentally verified. Since then, much research on the dynamic toroidal dipole usually with low-loss and high field concentration has been carried out, such as electromagnetic-induced transparency [ 9 ], absorption [ 10 ], circular dichroism [ 11 ], sensing [ 12 , 13 ], optical force [ 14 ], and so on [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ].…”

Review of Broadband Metamaterial Absorbers: From Principles, Design Strategies, and Tunable Properties to Functional Applications

“…Interference theory is widely used to illustrate profound principles of perfect absorption in MAs, [202][203][204] and the utility of this theory can also be found in the literature of numerous constructed BMAs. [198,[205][206][207][208] The BMA with ultra-broadband absorption consisting of a multilayer structure of periodic electric ring resonator arrays has been proposed, [198] as shown in Figure 4b. The interference theory constructed for this device has been modeled in Figure 4c, and it is analyzed that this structure can generate multiple interference effects between the resonator layer and the dielectric layer, which leads to a BMA harvesting a bandwidth of 3.85 THz with an average absorption of more than 90%.…”

“…The interference theory constructed for this device has been modeled in Figure 4c, and it is analyzed that this structure can generate multiple interference effects between the resonator layer and the dielectric layer, which leads to a BMA harvesting a bandwidth of 3.85 THz with an average absorption of more than 90%. [127] Demonstration of a polarization-insensitive BMA in the THz band using interference theory, [205] relying on structurally generated interference to achieve high absorption at 1.46-2.29 THz. A BMA constructed from a monolayer of MoS 2 provides the ability to achieve ≥90% absorption in the wavelength range of 389-517 nm, and the internal principle of broadband absorption was determined by using interference theory.…”

“…It is found that most of the relative absorption bandwidth of BMAs with absorbance more significant than 80% is only about 50%, while the relative absorption bandwidth with absorbance larger than 90% is usually lower. [104,205,207,453,478,[608][609][610][611][612][613] Insufficient absorption bandwidth (or relative absorption bandwidth) will limit their application prospects. Therefore, designing and realizing large absorption bandwidth, especially broadband absorption across the spectrum of specific application scenarios, is important in actual applications.…”

Ti3C2Tx MXene‐Based Superhydrophobic Broadband Terahertz Absorber with Large Pore‐Size Foam Architecture

“…Our work ignites the research interest in MXenebased porous EM absorbers in terahertz and microwave bands. [31][32][33] For most of the applications, the capability to stay dry and self-cleaning is necessary for a porous absorber. Liquid, ice, and dust on the surface will almost inevitably change the impedance-matching condition thus increasing the EM reflection.…”