Uniform near-field nanopatterning due to the field distribution control by oblique femtosecond laser irradiation to silicon and gold nanoparticles

We present near-field optical properties around silicon and gold nanoparticles aligned on a silicon substrate excited by oblique incidence femtosecond laser for nanohole processing. Near-field nanofabrication will open up smart applications for new optical devices with high-throughput processing. The near field around silicon and gold particles is explained by Mie scattering theory, while the near field around gold nanoparticles is explained by plasmon polaritons inside nanoparticles. With gold nanoparticles, theoretical study revealed that the incident laser energy is concentrated into the contact point between the particle and the substrate due to the image charge inside the substrate at any incident angles. With particles with a dielectric constant as high as silicon, the polarized charge shows a similar effect to the plasmon charge. Therefore the distribution of the concentrated energy provided with silicon nanoparticles is similar to that of gold nanoparticle.