Enhanced dual-band absorption of graphene mediated by an aluminum metastructure

Abstract

Graphene absorption from the visible to infrared spectrum has great potential and broad applications in miniature of modern optoelectronic biosensors and photodetectors. However, graphene has zero bandgap energy, which limits its absorption to 2.3% in the visible and infrared spectrums. Here, we propose a metastructure to optimize graphene absorption in the visible to near-infrared frequency regions. The metastructure, comprising an array of aluminum square blocks (Al-SBs) on a graphene layer, a silica spacer, and an Al reflector, is investigated for absorption enhancement. This work deciphers the effect of the periodicity of decorated Al-SBs on the evolution of dual-band absorption in single-layer graphene under normal incidence. The electromagnetic signatures of two excited modes indicate that surface plasmons and magnetic dipole plasmons are mediators of absorption. The investigation into the impact of geometrical parameters illustrates that the coexisting phenomena of a relative broad peak and a relative sharp peak have been achieved simultaneously with high efficiency. The dynamic manipulation of surface plasmons and magnetic dipole plasmons presents great potential for a diverse range of applications, such as sensing and imaging. By controlling the periodicity of Al-SBs, it is possible to achieve active control of surface plasmon resonance, and a detection range of 300 nm is observed. Dynamic control of the magnetic dipole plasmon is successfully achieved by modifying the electrical environment of the graphene layer, which is realized by altering the underlying spacer material. Collectively, the findings of this study demonstrate the significant potential of the suggested metastructure for its prospective applications in optoelectronic devices, including biosensors, photovoltaics, and photodetectors that rely on the dynamic control of surface and magnetic plasmon resonances.