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 diffractionunlimited 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 ~130 nm and ~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.
Bioinspired nanostructures have attracted increasing attentions and found widespread applications in various fields including material, chemical, mechanical and optical engineering because of their unparalleled physical advantages<sup>1</sup>. Honeycomb, a kind of porous structure, owns unique structure features, which enable its properties of low density, high mechanical strength, and high-energy-storage capacity<sup>2</sup>. The high quality of metal honeycomb structure with high uniformity, smooth metal surface, high-aspect-ratio sidewall and sharp corners of the triple junction is useful for plasmonic functional devices. Inspired by the building process of natural honeybee combs, we proposed an unconventional nanofabrication technique to produce high-quality gold nano-honeycombs with high-aspect-ratio (>10:1) and thin (<20 nm) sidewalls. As one of the important applications, the refractive index (RI) sensing behavior of the gold nano-honeycomb arrays was modeled and investigated numerically based on the surface plasmon polariton effect. The simulation results show that, in near-infrared region, the RI sensitivity is about 850 nm/RIU, which is approaching the theoretical limit<sup>3</sup>.