Ultrathin optical functional film and preparation method thereof

The invention belongs to the technical field of optical thin films, and relates to an ultrathin optical functional thin film and a preparation method thereof, and the ultrathin optical functional thin film comprises a reflecting layer, a dielectric layer and a light absorption layer which are sequentially arranged from bottom to top; wherein the light absorption layer is a nano-pillar array prepared from a three-dimensional topological insulator material, the thickness of the nano-pillar array is greater than or equal to 10 nm and less than or equal to 25 nm, and the thickness of the ultrathin optical function thin film is in a hundred nanoscale, and the ultrathin optical function thin film is used for efficiently absorbing light in a wave band of 400-1000 nm. The ultrathin optical functional film is simple in structure and preparation process, low in preparation cost, capable of efficiently absorbing full-band visible light and partial near-infrared band light, and easy to integrate with optical components a