Inverse-Designed Broadband Ultrathin Aperiodic Metacoatings Spanning from Deep Ultraviolet to Near Infrared

Abstract

The ability to actively control broadband light absorption and reflection ranging from deep-ultraviolet (DUV) to near-infrared (NIR), is crucial for various optical and optoelectronic applications. Herein, a novel type of ultrathin, lithography-free, and broadband aperiodic thin-film metamaterial coatings (metacoatings) is inverse-designed from DUV to NIR (190–1700 nm), which is composed of a series of deeply subwavelength tungsten oxide layers with graded refractive index profiles (by varying the deposited Ar gas pressures from 0.1 to 3.0 Pa) above an opaque aluminum layer. Experimental results show that these proposed aperiodic metacoatings can realize a transition from broadband strong absorption (as-deposited state) to high reflection (annealed state) from visible (VIS) to NIR (400–1700 nm), through thermal annealing techniques. The aperiodic metacoatings have an overall thickness of just ≈200 nm, with angle-insensitive up to 70° as well as are polarization-independent. Furthermore, vivid structural colors can be generated by rearranging the aperiodic tungsten oxide layers and finally employed in color display applications. These aperiodic metacoatings offer a very promising platform for many applications such as broadband photodetectors, thermophotovoltaics, information encryption devices, etc.