Omnidirectional, Broadband, and Polarization‐Independent Near‐Perfect Light Absorption from Surface Plasmonic Excitation of a Corrugated Au–SiO2–Au Structure Fabricated with a Self‐Assembled Silica Opal Template

Abstract

A corrugated metal–insulator–metal (cMIM) structural design for omnidirectional, broadband, and polarization‐independent near‐perfect light absorption (NPA) is proposed and demonstrated. The optimal structure consists of a (6 nm Au layer)–(70 nm SiO2 layer)–(90 nm Au layer) MIM structure on top of a self‐assembled silica opal template, which consists of monodisperse SiO2 nanospheres with an average diameter of 295 nm. The optical measurement demonstrates greater than 95% absorption for this optimal cMIM structure with incident light with wavelengths between 400 and 800 nm, and the incident angle varies from normal incidence to 60° off normal for both TE and TM polarizations. For the figure of merit (FOM) of the device performance, the spectral averaged absorption at normal incidence is calculated. The optimal cMIM structure demonstrates an FOM of 99.2%. Numerical simulations with rigorous coupling wave analysis (RCWA) and the finite difference time domain (FDTD) method to simulate the interaction between the incident light and the cMIM structure is carried out. The results qualitatively reproduce the structural dependence of the absorption of cMIM structures. They further indicate that multiple modes of surface plasmon polariton (SPP) excitation at various wavelengths are responsible for the NPA of the cMIM structure.

Keywords

• corrugated metal–insulator–metal structures
• finite difference time domain methods
• localized surface plasmon polaritons
• nanofocusing
• near-perfect light absorption
• rigorous coupling wave analysis