Ultrabroad antireflection urchin-like array through synergy of inverse fabrications by femtosecond laser-tuned chemical process

Eliminating the optical reflection of functional metal surfaces is crucial in many optical devices. However, minimizing the reflectivity of a metal surface over a wide band is an intractable task due to the high optical impedance between metal and air. Herein, an urchin-like composite micro/nanostructure with a highly effective antireflection property over an ultrabroad spectrum was prepared on a copper surface. To obtain this dual-scale and orderly urchin-like structure, a synergetic subtraction and additive micro/nanofabrication strategy is proposed. With the preprocessing of femtosecond laser, selective growth of nanostructures with specific morphologies can be achieved by chemical oxidation. This urchin-like morphology, combined with the light absorption capabilities of micron cones and nanowires, exhibits superior antireflection performance, and ultralow reflectance is attained at an ultrabroad spectrum comprising ultraviolet, visible, infrared, and far-infrared bands. This study provides a simple approach for the preparation of micro/nanostructures with high homogeneity and eminent reproductivity. Furthermore, the Cu(OH)₂/CuO heterogeneous urchin-like structures could serve as core functional components in fields of photovoltaic devices, stealthy materials, and chemical catalysis.