High-Quality Graphene-Based Tunable Absorber Based on Double-Side Coupled-Cavity Effect

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.

Simulation of a New CZTS Solar Cell Model with ZnO/CdS Core-Shell Nanowires for High Efficiency

“…jσ g ωε 0 t g , and according to Kubo's relation, the graphene surface conductivity, σ g , is calculated as the sum of intra band σ intra and inter band σ inter conductivity of graphene, and given by [55]:…”

“…It was also shown that when the graphene monolayer is sandwiched between two dielectric layers, just like absorption, an increase in the electric field intensity on the upper and lower faces of the graphene layer is observed. Add to this that with the tuning of the geometric parameters, this device can serve as a modulator and chemical/biochemical sensor [55].…”

“…Although such a model is difficult to achieve due to the growth deposition of nanowires through the graphene layer, models based on the same principle have been studied and implemented, and have shown the improved optical and electrical performance of the solar cell [55,59]. Experimentally, ZnO nanowires are grown by electrochemical process and a CdS shell is synthesized on ZnO nanowires using the hydrothermal method [15,52,55,59]. This same hydrothermal growth approach can be used to push the nanowires through the graphene layer [15].…”

Enhancing modulation performance by design of hybrid plasmonic optical modulator integrating multi-layer graphene and TiO2 on silicon waveguides

“…The tunable electro-absorption and electro-refraction properties of graphene make it highly suitable for photonic applications, such as integrating graphene into optical modulators on Si photonic platforms [12]. Numerous research studies have endeavored to design optical devices with enhanced performance characteristics by incorporating graphene, exemplified by optical switches and plasmonic absorbers [13,14]. This phenomenon results in gate-controlled optical absorption in graphene within a hybrid structure, demonstrating an essential part of on-chip integrated photonic devices [15].…”