Retaining and characterising nano-structure within tapered air-silica structured optical fibers

Air-silica fiber 125m in diameter has been tapered down to ~15m. At this diameter, it is commonly assumed that the nanostructured fiber holes have collapsed. Using an Atomic Force Microscope, we show this assumption to be in error, and demonstrate for the first time that structures several hundred nanometers in diameter are present, and that hole array structures are maintained. The use of Atomic Force Microscopy is shown to be an efficient way of characterising these structures.