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

Design of terahertz metamaterial absorbers with switchable absorption functions utilizing thermal and electrical dual-modulation strategies

This work demonstrates a dual-functional tunable terahertz metamaterial absorber based on thermally controllable vanadium dioxide (VO2) and electrically tunable graphene. The switchable absorption functions could be obtained in the same metamaterial, which consists of alternating stacked cross-cut graphene disks (CGDs) and VO2 square rings (VSRs) separated by an ultra-thin dielectric film placed on a continuous gold mirror. The metallic state of VSRs is the dominant factor for the broadband absorption function, resulting in a broadband absorption of 4.746 THz. Based on this, the Fermi energy level of CGDs increases to 0.7 eV, which could broaden the absorption bandwidth to 5.398 THz. When the VSRs are in the insulating state, CGDs dominate the absorption, and the suggested device switches to the dual-band absorption function. These two absorption peaks appear to be larger than 97% and their frequencies could be dynamically controlled by the Fermi energy level of CGDs. In addition to the excellent absorption characteristics of dynamic switching of two different functions, polarization insensitivity and large-angle tolerance are also advantages of this work, which could provide new insights and guidance for the study of dynamically tunable metamaterial absorbers.

Enhancing modulation performance by design of hybrid plasmonic optical modulator integrating multi-layer graphene and TiO2on silicon waveguides

A novel way to enhance modulation performance is through the design of a hybrid plasmonic optical modulator that integrates multi-layer graphene and TiO2on silicon waveguides. In this article, a design is presented of a proposed modulator based on the use of the two-dimensional finite difference eigenmode solver, the three-dimensional eigenmode expansion solver, and the CHARGE solver. Leveraging inherent graphene properties and utilizing the subwavelength confinement capabilities of hybrid plasmonic waveguides (HPWs), we achieved a modulator design that is both compact and highly efficient. The electrical bandwidthf3dBis at 460.42 GHz and it reduces energy consumption to 12.17 fJ/bit with a modulator that functions at a wavelength of 1.55μm. According to our simulation results, our innovation was the optimization of the third dielectric layer's thickness, setting the stage to achieve greater modulation depths. This synergy between graphene and HPWs not only augments subwavelength confinement, but also optimizes light-graphene interaction, culminating in a markedly enhanced modulation efficiency. As a result, our modulator presents a high extinction ratio and minimized insertion loss. Furthermore, it exhibits polarization insensitivity and a greater bandwidth. Our work sets a new benchmark in optical communication systems, emphasizing the potential for the next generation of chip-scale with high-efficiency optical modulators that significantly outpace conventional graphene-based designs.

Design and Implementation of Graphene-Based Tunable Microwave Filter for THz Applications

A reconfigurable Substrate-Integrated Waveguide (SIW) filter operating in the THz region was designed in this work. Two SIW resonators were coupled through a magnetic iris to form a second-order filter with a double-layer substrate. The first substrate was silicon of permittivity 11.9; on top of it, silicon dioxide of permittivity 3.9 was placed. The ground and upper plane were composed of gold plates. Graphene material was then used for the tunability of the filter. A thin graphene sheet was sandwiched between the silicon dioxide substrate and the upper gold plate. An external DC bias voltage was then applied to change the chemical potential of graphene, which, in turn, managed to change the operational center frequency of the filter within the range of 1.289 THz to 1.297 THz, which translated to a bandwidth range of 8 GHz. The second part of this work centered on changing the aspect ratio of the graphene patch to change the center frequency. It was observed that the frequency changed within the range of 1.2908 THz to 1.2929 THz, which gave a bandwidth of 2.1 GHz change.

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

The numerical modeling of Cu2ZnSnS4 solar cells with ZnO/CdS core-shell nanowires of optimal dimensions with and without graphene is described in detail in this study. The COMSOL Simulation was used to determine the optimal values of core diameter and shell thickness by comparing their optical performance and to evaluate the optical and electrical properties of the different models. The deposition of a nanolayer of graphene on the layer of MoS2 made it possible to obtain a maximum absorption of 97.8% against 96.5% without the deposition of graphene.The difference between generation rates and between recombination rates of electron–hole pairs of models with and without graphene is explored.The electrical parameters obtained, such as the filling factor (FF), the short-circuit current density (Jsc), the open-circuit voltage (Voc), and the efficiency (EFF) are, respectively, 81.7%, 6.2 mA/cm2, 0.63 V, and 16.6% in the presence of graphene against 79.2%, 6.1 mA/cm2, 0.6 V, and 15.07% in the absence of graphene. The suggested results will be useful for future research work in the field of CZTS-based solar cells with ZnO/CdS core-shell nanowires with broadband light absorption rates.