Extending femtosecond laser fabrication of micro- and nanoscale structures from a planar to non-planar metal surface

Micro- and nanoscale structures on a material surface formed by femotosecond laser processing have greatly changed its optical characteristics. In this work, the coloring of Al surface has been realized with scanning focused femtosecond laser beam on the Al surface. We further apply femtosecond laser filamentation to form micro- and nano-structures on a spherical Al surface, resulting in a black appearance of the spherical Al. This work opens ways to fabricate strong light-trapping micro- and nano-structure on a non-planar surface without the complexity of a 4-axis sample control.