Large-area fabrication of metasurface on microspheres based on colloidal assembly and femtosecond ablation

A nanofabrication method of metasurfaces based on colloidal assembly and femtosecond ablation is proposed and demonstrated. The metasurfaces on microspheres own the advantages of large area, low cost, long-range periodicity, high light-scattering efficiency and compatibility with liquid crystal display (LCD) manufacturing. Here, the diffraction-unlimited nano-ablation is realized on the gold layer hemispherically coated on the assembled silica microspheres. The radius of ablated spot and half-pitch of ablated slit achieved in the experiment are similar to 130 nm and similar to 30 nm, respectively. Through changing the incidence angle of the femtosecond laser beam, some complicated ablation nanopatterns consisting of spots and slits would be realized.