Direct patterning of three-dimensional periodic nanostructures by surface-plasmon-assisted nanolithography.

The technical applications of three-dimensional (3D) nanostructures demand a fabrication technique that is convenient and yet offers design flexibility. We describe here a nanofabrication technique called surface-plasmon-assisted three-dimensional nanolithography (3D-SPAN). By utilizing optical near-field interference patterns generated by surface plasmons (SPs), we have fabricated different 2D/3D periodic polymeric nanostructures in a typical photolithography setup. We have also shown here that the nanostructures fabricated by 3D-SPAN can be controlled easily in terms of size, layout, and defects by designing the SPAN mask. Because of its design flexibility and fabrication convenience, 3D-SPAN could be used to develop "photonics on a chip", where signal processing is carried out by photons instead of electrons and be extended to other applications of direct-writing 3D functional nanostructures.