An experimental and theoretical study

Abstract

In this contribution we present recent experi- mental and theoretical results on local near-field assisted laser ablation. Along these lines, we have generated sub- diffraction sized nanostructures on fused silica substrates, exploiting the local near fields of highly ordered triangu- lar gold nanoparticle arrays generated by nanosphere lithog- raphy. After preparation, the nanoparticle arrays were ir- radiated with a single 35 fs long laser pulse with a cen- tral wavelength of λ = 790 nm. The pulse energy was set to E = 3.9 µJ, resulting in a fluence well below the abla- tion threshold of the fused silica substrates. In addition, 3D electromagnetic simulations using a finite integration tech- nique in time domain have been performed. The simulations demonstrate that indeed the local field in the vicinity of the tips of the triangular nanoparticles overcome the ablation threshold and easily explain the generated nanostructures. Most importantly, the simulations show, that higher order modes contribute to the ablation process. These modes cause ablation along the side edges of the nanoparticles. Finally, we demonstrate, that the optical properties of the triangular nanoparticles, which can be tuned by their morphology, are