Nanometer-scale laser direct-write using near-field optics

This article summarizes research on laser-based processing and structuring of materials at the nanoscale using optical near-field schemes. Both apertureless and tapered fiber near-field scanning optical microscope probes can deliver highly confined irradiation at sufficiently high intensities to cause morphological and structural changes in materials at the nanometer level. The energy emitted by the probes and the absorption within the target material are predicted by carrying out calculations of the near-field electromagnetic distribution. The effects of shrinking laser beam dimensions compete with the energy diffusion into the target material. Expedmental results have shown well-controlled subtractive material modification with minimum feature size in the neighborhood of 10 nm. Precise patterning can be achieved via laser-assisted chemical etching. Control of the nucleation of nanostructures via rapid melting and crystallization is demonstrated. The article concludes with an outlook to applications.