Broadband Light Absorber of Gold-Coated Moth-eye Film

Motheye films have pillars of circular truncated cones with dimensions of one-hundred nanometers as bristles. A motheye film coated with gold of 30 nm thickness shows significant broadband light absorption (BLA) over the visible wavelengths. This property stems from the pillars coated with gold, which efficiently confine and localize the light around the pillars. The measured spectra of reflectance, transmittance, and absorptance are supported by those calculated by the finite-domain time difference method. We modeled the pillars as cylinders or circular truncated cones, and calculated their spectra. Among these models, the circular truncated cones coated with gold have the highest BLA property. The gold-coated motheye film provides us with a large-area BLA material that is useful for optical devices.