Symmetry-wise nanopatterning and plasmonic excitation of ring-like gold nanoholes by structured femtosecond laser pulses with different polarizations

Abstract

Low- and ultralow-energy tightly focused 200 fs, 515 nm donut-shaped laser pulses at 0.25 and 0.65 NA focusing were used for single-shot ablative pulse-energy scalable nanopatterning of 50 nm thick gold film and the following plasmonic excitation of dye monolayer photoluminescence (PL) in the fabricated nanostructures, respectively. The same pulses at much lower, non-ablative nanojoule energies, and the same focusing and linear, azimuthal, or radial polarizations provided efficient spectrally and symmetry-matched excitation of both localized and delocalized surface electromagnetic modes in the separate, ring-like through holes and their arrays in the film envisioned by our modeling, thus resulting in a polarization-sensitive yield of rhodamine 6G dye PL. The demonstrated consistency between the symmetries of the donut-shaped low-energy photo-exciting laser beam, its polarization state, and the donut-shaped gold nanostructures, produced by the same beam at high, ablative pulse energies, paves the way to smart, self-consistent nanofabrication and plasmonic sensing, when the structured light interacts with the consistently structured matter.