Broadband absorption using all-graphene grating-coupled nanoparticles on a reflector

Abstract

In this paper, the hybridized localized surface plasmon resonances (LSPRs) of a periodic assembly of graphene-wrapped nanoparticles are used to design a nanoparticle assisted optical absorber. Bandwidth enhancement of this structure via providing multiple types of plasmonic resonances in the associated unit cell using two densely packed crossly stacked graphene strips is proposed. The designed graphene strips support fundamental propagating surface plasmons on the ribbons, and gap plasmons in the cavity constructed by the adjacent sections. Graphene strips exhibit a hyperbolic dispersion region in the operating spectrum and assist in the bandwidth enhancement. Moreover, since the nanoparticles are deposited on the top strips, real-time biasing of them can be easily conducted by exciting the surface plasmons of the strip without the necessity to electrically connect the adjacent nanoparticles. The overall dynamic bandwidth of the structure, using a two-state biasing scheme, covers the frequencies of 18.16–40.47 THz with 90% efficiency. Due to the symmetry of the structure, the device performs similarly for both transverse electric (TE) and transverse magnetic (TM) waves and it has a high broadband absorption rate regarding different incident angles up to 40°. Due to the presence of 2D graphene material and also using hollow spherical particles, our proposed absorber is also lightweight and it is suitable for novel compact optoelectronic devices due to its sub-wavelength dimensions.

Efficient and high-quality absorption enhancement using epsilon-near-zero cylindrical nano-shells constructed by graphene

“…The minimum gap distance is set to 5 nm, which is sufficient for neglecting the nonlocal effects, dominant for the gap distances below 2 nm 80 . As the figure confirms, the mutual coupling of the plasmonic resonances for smaller interelement spacings results in the red shift of the resonance spectrum and its broadening 81 . The maximum achievable absorption rate of 50% for an array of free-standing polarizable particles is observed for different optimum periodicities when the quality of the graphene material is altered.…”

Photovoltaic and Photothermal Solar Cell Design Principles: Efficiency/Bandwidth Enhancement and Material Selection

“…To widen the bandwidth of the resonant absorbers, the design of multilayered structures and the combined use of elements with different dimensions to excite multiple resonances are proposed [37][38][39][40]. In the device shown in Figure 5a, the hyperbolic nature of the dispersion band supported by the densely packed graphene strips, along with propagating and localized surface plasmon resonances, respectively, provided by the gap plasmons and plasmonic spherical particles, are effectively used to enhance the absorption bandwidth of the multilayer structures [41,42]. Considering this idea, Figure 5b shows a thin film amorphous silicon (a-Si) photovoltaic solar cell in which silver nanoparticle arrays are embedded in the surface and active layer, respectively, being responsible for absorption enhancement in the lower and higher wavelengths [22].…”

A review of perfect absorbers based on the two dimensional materials in the visible and near-infrared regimes

“…Thus, some broadband h-BN-based absorbers have been reported in recent years [91][92][93]. Inspired by the idea of slowlight waveguide, a lot of researchers have considered using hyperbolic metamaterial to enhance the absorption of 2D materials and propose broadband absorber, although most of the reports are focused on mid infrared and terahertz band [94][95][96][97][98][99]. Not long ago, in the visible band, Pourmand et al [85] designed and investigated a broadband absorber based on the hyperbolic metamaterial, which consists of periodically arranged gold and methyl ammonium lead iodide (MAPbI 3 ) nanolayers, as shown in figure 8.…”