First-approximation simulation of dopant diffusion in nanostructured silica optical fibres

The production of arrays of nanoscale particles is of interest for many current scientific endeavours. Established techniques such as lithography are suitable for the task, but come with high equipment costs. An alternative is to use the distribution of glass dopants in a drawn optical fibre to define the nanometre scale pattern. The structures are then revealed by etching the glass with a selective acid. One of the critical factors when working with doped glasses is the effect of dopant diffusion encountered in the manufacturing phase as excessive diffusion will destroy the pattern. To aid in calculating the effects of diffusion, a simulation program was written which models the glass structure under various diffusion conditions likely to be encountered in the fibre production. Outputs of the simulation package are found to correlate well with experimental results. As a demonstration of the nanostructures produced, the etched fibres were employed as surface-enhanced Raman scattering (SERS) substrates.