Bidirectional Absorber from Broadband to Narrowband Using Epsilon-Near-Zero material and Plasmonic Structures

In this study, a bidirectional absorber with broadband and narrowband absorption capabilities is designed and analyzed. the structure consists of two sides: the top side is composed of au disks and indium tin oxide (ito) as an epsilon-near-zero (enz) material for broadband absorption in the near-infrared region, whereas the bottom side features a simple metal-dielectric-metal configuration for narrowband absorption. broadband absorption, covering more than 90% of the spectrum within the wavelength range of 1470–2290 nm, results from the coupling of the enz modes with the plasmon modes. narrowband absorption with near-unity efficiency at a wavelength of 1550 nm was achieved because of the localized plasmonic resonances in the al disk arrays. the numerical simulation results demonstrate that this structure can achieve nearly perfect absorption in both light propagation directions (+z and −z) through the optimization of geometric parameters. in addition, this design has potential applications in color filters, energy storage systems, and advanced optical devices.