Tuning nanopatterns on fused silica substrates: a theoretical and experimental approach

Abstract

In this study we develop a novel approach to tune nanopatterns on fused silica substrates exploiting the polarization dependence of the strongly localized near field of highly ordered triangular nanoparticle arrays. For this purpose such arrays were prepared by nanosphere lithography on fused silica substrates and subsequently irradiated with single 35 fs long laser pulses. The irradiation leads to the excitation of localized surface plasmon polariton resonances, followed by ablation of the nanoparticles and partially of the substrate. By this means, nanostructures were generated on the substrate surface, reflecting the local fields in the vicinity of the triangular nanoparticles. Depending on the applied fluence, small holes as well as extended nanostructures with dimensions well below the diffraction limit have been created. Furthermore, by rotating the linear polarization of the laser light by 90° with respect to the orientation of triangular nanoparticles, different plasmon modes have been excited, which in turn, alter the local field distribution. As a result, either nanochannels or bone like shaped nanogrooves in a chequered structure were generated on the fused silica substrates. Finite-difference time-domain simulations demonstrate, that the results can, in fact, be explained by the enhanced near field distribution, which is dominated by the excitation of localized surface plasmon polariton resonances in the triangular nanoparticles. It is shown, that the fluence and the polarization of the laser light are the key parameters in nanogroove and nanochannel formation.