In the work, a statistical approach coupled with the use of tailor-made spheres allows the precision and reproducibility of the laser nanomachining to be related to the size dispersion of the nanospheres.

To produce the nanostructured membranes, the team first prepares monodisperse silica nanospheres and then assembles monolayers of the material on target substrates. Next using a nanosecond laser pulse, the group fabricates beautifully ordered mesoporous membranes thanks to the interaction of the light with the nanospheres. During this nanodrilling process, the ablated products eject the spheres by momentum transfer and simultaneously clean the substrate of any residual contaminant.

In the work, the researchers focused on the optical near-field aspects associated with preparing high-precision membranes. By statistical analysis, the scientists demonstrated that the concept of optical Mie resonances can lead to strong local field changes for sphere sizes in the range 550–725 nm. In this range, the data indicate that an extremely narrow size distribution of nanospheres (σ <<25 nm) is required to produce well defined and defect-free membranes in the full range of operative laser fluences.

Full details can be found in the journal Nanotechnology.