Perfect Optical Absorbers Based on Plasmon Resonances in Subwavelength-Patterned Gold Thin Films

Photon absorption is a fundamental part of the operation of photodetectors, solar cells, photothermal devices, and optical filters. Perfect absorbers are materials that can efficiently absorb nearly all incident radiation either in a narrow or broad wavelength range. Perfect light absorption in metals has been achieved using thick porous foams, impedance matching lossy films, and metallic nanopillars or needles with a gradual refractive index change. Here we present a subwavelength patterned gold thin film that is capable of absorbing 97% of incident light in the visible range 320–650 nm. Optical absorption is high (>90%) even at high incidence angles.