Femtosecond laser near-field ablation mediated with Mie resonance scattering by high dielectric constant particles with small size parameter

Abstract

We present theoretical and experimental results on near-field ablation mediated with Mie resonance scattering by high dielectric constant particles with small size parameter for establishing a new downsizing technique for nanopatterning. In this article, we first describe a comparative study of the near-field properties on substrates using metallic and dielectric nanoparticle. The 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. We then demonstrate the nanoablation using a Mie resonance high dielectric constant small particle. Theoretical calculations clarified that the maximal enhancement factor and spot diameter close to the smallest size are obtainable on both low-refractive-index (SiO2) and high-refractive-index (Si) substrates using a 200-nm Mie resonance dielectric particle (n∼2.7) at magnetic quadrupole mode with 400-nm excitation wavelength. Experimental results with 200-nm amorphous TiO2 particles (n=2.66+0.024i) by 400-nm femtosecond laser irradiation verified that clear circular nanoholes with about 100 nm in diameter are fabricated on both substrates even with laser fluence lower than a half ablation threshold of the bare substrates. Highly dense two-dimensional nanohole array can be fabricated by applying arrayed particles obtained from self-assembly process. Optical field interaction such as inter-particle multiple scattering should be considered and then an optimal refractive index of particle is different from the single particle case.The obtained results indicate that application of high dielectric constant particles with optimal refractive index is a promising technique for downsizing the fabricated nanoholes.We present theoretical and experimental results on near-field ablation mediated with Mie resonance scattering by high dielectric constant particles with small size parameter for establishing a new downsizing technique for nanopatterning. In this article, we first describe a comparative study of the near-field properties on substrates using metallic and dielectric nanoparticle. The 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. We then demonstrate the nanoablation using a Mie resonance high dielectric constant small particle. Theoretical calculations clarified that the maximal enhancement factor and spot diameter close to the smallest size are obtainable on both low-refractive-index (SiO2) and high-refractive-index (Si) substrates using a 200-nm Mie resonance dielectric particle (n∼2.7) at magnetic quadrupole mode with 400-nm excitation wavelength. Experimental...