Antireflective surfaces for astro-photonic applications

Antireflection patterns for optical elements used in astro-photonic applications require optimisation for different wavelengths, a defined angular selectivity and have to be made on large curved surfaces. Sputtered film of tens-of-nm of gold was annealed at 500°C for 1 hour to form a pattern of nano-islands used as a mask for plasma etching. Separation between islands depended on the annealing time and an initial film thickness and provides a method to control a characteristic length between etched nano-pillars. Fabricated surfaces were characterised by transmission and reflection spectroscopy.