Structurally tunable plasmonic absorption bands in a self-assembled nano-hole array

In this paper, we demonstrate a theoretical and experimental study on a nano-hole array that can realize perfect absorption in the visible and near-infrared regions. The absorption spectrum can be easily controlled by adjusting the structural parameters including the radius and period of the nano-hole, and the maximal absorption can reach 99.0% in theory. In order to clarify the physical mechanism of the absorber, we start from the extraordinary optical transmission supported by the nano-hole array in a thin metallic film coated on a glass substrate, and then analyse the perfect absorption in the metal–insulator–metal structure. The surface plasmon modes supported by the nano-hole array are completely clarified and both the FDTD simulation and waveguide theory are used to help us understand the physical mechanism, which can provide a new perspective in designing this kind of perfect absorber. In addition, the nano-hole array can be fabricated by simple and low-cost nanosphere lithography, which makes it a more appropriate candidate for spectroscopy, photovoltaics, photodetectors, sensing, and surface enhanced Raman scattering.