Figure shows the experimental and FDTD simulated reflection spectra of MIM metasurfaces with different metallic elements for the SiO 2 dielectric spacer of 300 nm. All the spectral data with different SiO 2 thicknesses are summarised in Figures and for the experimental and simulated results, respectively. HEA alloys are characterized by forming a low reflection condition over a wide range of wavelengths and relatively narrow resonance line widths. In contrast, Au, Ag, and Cu metasurfaces have narrow resonance line widths but low reflection only over a limited range of wavelengths. For example, SiO 2 films of 100 nm and 200 nm thicknesses show lower reflection over a broader range than 300 nm thickness, but the range is narrower than that of HEA. In contrast, Pt and Pd have a more comprehensive range of low reflections, but their resonance spectra are broad.