Mie scattering and resonant plasmon polaritons for nano-ablation patterning

This paper describes the comparative study of near-field nano-processing of glass and silicon by use of metallic nano-particle and dielectric nano-particle excited by an 820 nm near-infrared femtosecond laser pulse. Near electromagnetic field around metallic nano-particle and dielectric particle shows quite unique properties on the substrate to be near-field processed. It is found that the existing thought that the use of the metallic particle is better than the dielectric particle in a much smaller particle size region than excitation wavelength is NOT always correct. As for near-field enhancement on low refractive index glass substrates by the dielectric particle with appropriate refractive index, an enhancement factor at the TE1 (magnetic dipole mode) resonance mode is found to be higher than that induced by gold particle even at the TM1 (electric dipole mode) resonance mode of gold particle. Conversely, on a high refractive index substrate like silicon, the near-field enhancement factor becomes larger by use of the gold particle at the same particle size. This significant change of the enhanced field intensity stems from the different nature of power flow based on the image charge induced in the substrate. These results indicate that the best combination of the particle and substrate for efficient localized near-field nano-processing is important for selecting either the metallic or dielectric particle. The obtained result gives a useful means for the particle selection and understanding of near-field interaction physics with substrate for efficient nano-processing of the substrate surface. Finally, these theoretical results have been verified by experiment.