Polarization-Selective Bidirectional Absorption Based on a Bilayer Plasmonic Metasurface

Abstract

We propose an alignment-free and polarization-selective bidirectional absorber composed of a one-dimensional bilayer Au grating array buried in a silicon nitride spacer. The absorptivity of the designed structure is more than 95% (77%) under normal forward (backward) TM-polarized light incidence, and is more than 80% (70%) within a forward (backward) incident angle up to 30°. The great bidirectional absorption performance is illustrated by the resonance coupling of the surface plasmon polaritons (SPPs) resonance, the propagating surface plasmon (PSP) resonance and the localized surface plasmon (LSP) resonance under TM-polarized wave illumination. Moreover, the excitation of the Fano-like resonance mode of the proposed metasurface can produce two significantly different peaks in the absorption spectrum under the oblique TM-polarized incidence, which is beneficial for the plasmon-sensing application. Therefore, the proposed bidirectional metasurface absorber can be a candidate in the application of optical camouflage, thermal radiation, solar cells and optical sensing.

Ultrathin Narrowband and Bidirectional Perfect Metasurface Absorber

“…Additionally, the highest microwave attenuation occurs around the resonance frequency of 10 GHz, as indicated by the maximal value of the imaginary part of the relative refractive index (Im(n)). The high absorption level of the bidirectional MSA is primarily due to the fundamental electrical and magnetic resonance loss, which is significantly different from the coherent absorption mechanism employed by previous optical absorbers [44][45][46][47][48][49]. The real part of the equivalent relative wave impedance (Re(z)) is approximately unity, while the imaginary part (Im(z)) is near zero at the absorption frequency, indicating that the wave impedance of the designed bidirectional MSA can be closely matched to free space around the resonance frequency.…”

“…However, most of the current designs only allow absorption of EM waves in one direction while reflecting waves in the other due to the use of a complete metal film as the ground plane. The potential application prospects of MSAs can be further expanded by implementing bidirectional perfect absorption [44][45][46][47][48][49][50][51][52]. Direction-insensitive absorption is a less explored and more challenging area in MSAs.…”