Graphene perfect absorber of ultra-wide bandwidth based on wavelength-insensitive phase matching in prism coupling

Abstract

We proposed perfect absorbers of ultra-wide bandwidths based on prism coupling with wavelength-insensitive phase matching, which consists of three dielectric layers (Prism-Cavity-Air) with monolayer graphene embedded in the cavity layer. Due to inherent material dispersion of the dielectric layers, with the proper choice of the incidence angle and the cavity thickness, the proposed perfect absorbers can satisfy the phase matching condition over a wide wavelength range, inducing enormous enhancement of the absorption bandwidth. The requirement on the material dispersions of the prism and the cavity layer for the wavelength-insensitive phase matching over a wavelength range of the interest has been derived, and it has been demonstrated that the various kinds of materials can meet the requirement. Our theoretical investigation with the transfer matrix method (TMM) has revealed that a 99% absorption bandwidth of ~300 nm with perfect absorption at λ = 1.51 μm can be achieved when BK7 and PDMS are used as the prism and the cavity layer, respectively, which is ~7 times wider than the conceptual design based on the non-dispersive materials. The full width at half maximum of our designed perfect absorber is larger than 1.5 μm.

Towards Mirror-Less Graphene-Based Perfect Absorbers

“…Here, we will address graphene perfect absorbers (GPAs). Over the past decade, to construct GPAs, various configurations have been proposed, such as asymmetric cavities using multiple layers [16][17][18][19][20], gratings or photonic crystals [21][22][23][24][25][26][27][28][29][30][31][32][33], metamaterials [34][35][36][37][38][39][40], and prism couplers [41][42][43][44]. Previous reviews on GPAs have mainly focused on categorization in terms of absorption bandwidth (for example, narrowband, dual-band, broadband) or their operating wavelength ranges (for example, Visible to THz band) [7][8][9][10].…”

Random Graphene Metasurfaces: Diffraction Theory and Giant Broadband Absorptivity

“…[13], omega-shaped graphene patterns were designed for using as a wide-incident-angle absorber over more than 1 THz band. A wide absorption bandwidth is achievable in a multilayer system with embedded graphene sheet [14], with the perfect absorption for specific incident angle and layer thickness. The broadband absorption in the THz range can also be realized in the planar structures composed of five layers of graphene due to modulation of the graphene chemical potential [15], as well as in singular graphene gratings [16].…”

Magneto-tunable terahertz absorption in single-layer graphene: A general approach

“…Note that this amount of absorption is so impressive for a material with a 0.34 nm thickness. However, in general this amount of light absorption is considered to be very low and far from being used for desirable goals over a broad spectrum especially at the far-infrared and THz spectral ranges [17,20,21].…”

“…So far, several techniques have been introduced in order to enhance greatly the amount of light absorption of graphene in terms of theoretical and experimental approaches [22,23]. A long list of methods can be funded in at [20,21] for one that is interested to study which every method has its advantages and applications. Some methods are based on placing or embedding graphene in photonic crystals in order to achieve higher absorption [22,23,24,25].…”