Metasurface fabrication was performed as described elsewhere in more detail ? In short, 5 nm Cr and 200 nm Au were thermal deposited on a silicon substrate first. After depositing 5 nm Cr, set of samples with SiO 2 layers from 100 nm to 500 nm (with a 100 nm step) were deposited by electron-beam (EB) evaporation. After, an electron beam lithography (EBL) resist was spin-coated, and EBL exposure was performed to define the top-layer metallic nanostructures. After development, Cr 5 nm and various metals were deposited, and lift-off followed. Five metal alloys target were purchased (Tanaka Precious Metal Co., Ltd.) to form HEA by sputtering.