Patternable fabrication of hyper-hierarchical metal surface structures for ultrabroadband antireflection and self-cleaning

摘要

The capabilities to reduce light reflection have essential importance for various critical applications. Realistic antireflection surfaces are required to satisfy the comprehensive demands in broadband effectiveness, flexible fabrication, and performance stability. Here, we propose and experimentally demonstrate a type of highly disordered hyper-hierarchical micro-nano structures formed on the surfaces of metals such as Cu, which have the significant capability in absorbing light over the ultrabroadband spectrum from ultraviolet to far-infrared. Average hemispherical reflectance of similar to 2.4%, similar to 5.5%, and similar to 6% is achieved in the wavelength ranges of 400-800 nm, 200-2000 nm, and 2.5-25 mu m respectively, reaching an average absorptance of similar to 94% within 0.2-25 mu m The specular reflectance in the long wavelength range of 25-300 mu m is also dramatically reduced with respect to the original Cu surface. Such an ultrabroadband antireflection structure is fabricated by a non-contact, maskless, one-step femtosecond laser direct writing approach, making it flexible to be prepared in desired patterns. The hyper-hierarchical structure and its ultrabroadband antireflection property keep robust and stable during harsh aging tests. In addition to the antireflection property, the hyper-hierarchical structure also exhibits excellent self-cleaning performance. All these advantages in ultrabroadband effectiveness, patterning flexibility, structural robustness, as well as self-cleaning, make it promising for practical applications.