A proposal of a perfect graphene absorber with enhanced design and fabrication tolerance

Abstract

We propose a novel device structure for the perfect absorption of a one-sided lightwavve illumination, which consists of a high-contrast grating (HCG) and an evanescently coupled slab with an absorbing medium (graphene). The operation principle and design process of the proposed structure are analyzed using the coupled mode theory (CMT), which is confirmed by the rigorous coupled wave analysis (RCWA). According to the CMT analysis, in the design of the proposed perfect absorber, the HCG, functioning as a broadband reflector, and the lossy slab structure can be optimized separately. In addition, we have more design parameters than conditions to satisfy; that is, we have more than enough degrees of freedom in the device design. This significantly relieves the complexity of the perfect absorber design. Moreover, in the proposed perfect absorber, most of the incident wave is confined in the slab region with strong field enhancement, so that the absorption performance is very tolerant to the variation of the design parameters near the optimal values for the perfect absorption. It has been demonstrated numerically that absorption spectrum tuning over a wider wavelength range of ~300 nm is possible, keeping significantly high maximum absorption (>95%). It is also shown that the proposed perfect absorber outperforms the previously proposed scheme in all aspects.

A Wide Incident Angle, Ultrathin, Polarization-Insensitive Metamaterial Absorber for Optical Wavelength Applications

“…Anti-parallel current density from the metal layer to the metal resonator creates a loop. Artificial magnetic dipolar moment rises by the current density which is interrelated highly with the H-field [44], [117]. Therefore, the structure creates an excitation for the H-field and insinuates a very strong magnetic resonant dipole and creates a very good absorbance for the whole optical region.…”

“…However, these may not be the only reasons for a nearperfect MMA. Perfect impedance match of the metal with the free space of the solar spectrum [37], [38], the plasmonic resonance characteristics of the dielectric layer [39], [40], a symmetrical structure resonator with good confinement of the EM wave [41], [42], and a good E-field, H-field and distributed surface charge are also reasons for high absorption [43], [44]. MMA may also consist of two-layer [45], fourlayer [46], [47], multilayer stacks [48]- [50] along with most common three-layer structure.…”

Implementation of Atomically Thick Graphene and Its Derivatives in Electromagnetic Absorbers

“…Generally, graphene are used as a continuous layer or patterned structure in metasurface absorbers. On one hand, continuous graphene layer can be combined with patterned metal [94][95][96][97] or dielectric layers [21,24,83,[98][99][100] to couple the incident wave into resonant mode. On the other hand, graphene can also be patterned into periodic unit cells to support a single [101] or multiple resonant modes [26,[102][103][104] for EM wave absorption.…”

A Multi-Band Near Perfect Polarization and Angular Insensitive Metamaterial Absorber With a Simple Octagonal Resonator for Visible Wavelength

“…Metal layers prevent the propagation of the EM waves, and a coupling capacitance is constructed between the backlayer and the resonator in an MA with the help of a dielectric substance [17], [18]. Plasmonic resonance characteristics of a dielectric substrate [19], [20], perfect impedance match [21], [22], symmetric structure of the resonator [23], [24], and a good E-field, H-field and surface charge distribution [25], [26] causes high absorption of an PMA. Most common MA absorber structures are three-layered structures [27], [28], but there are also two-layered [29], four-layered [30], [31], multi-layered stacks [32]- [35].…”