Polarization insensitive plasmonic stacked multilayer metasurface with deep nanohole cavity as multi-band absorber

Abstract

A metal-dielectric stacked multilayer plasmonic metasurface containing square array of deep cylindrical nanohole cavity in layer-pairs is demonstrated to achieve polarization insensitive multiresonant near perfect absorption in the visible-near infrared (Vis-NIR) regime (500–1600 nm). Finite difference time domain (FDTD) computation is carried out to study the optical absorption properties. Four resonant absorption peaks with absorption strength in the range of 80–100% are observed. Studies show low wavelength (<900 nm) resonant absorptions due to surface plasmon polariton (SPP) excitation and cavity modes, and high wavelength (>900 nm) absorptions due to magnetic resonance confining magnetic near-fields at the dielectric region between two metal layers. A systematic increase in number of layer-pairs shows increase in peak absorption strength and blue-shifts in resonant wavelengths. Resonant condition and hence, optimized structure can be obtained by manipulating suitably the layer-pair thickness, cavity filling materials and unit cell period. It is observed that the proposed metasurface is completely insensitive to linearly, and left and right circularly polarized lights (LCP, RCP), and has large launch angle tolerance of ~25 degrees. Simplistic design, multi-band absorptions, polarization insensitivity and launch angle tolerance make the metasurface highly suitable for integrated optoelectronic devices for Vis-NIR detection.