Nanoscale reshaping of resonant dielectric microstructures by light-driven explosions

Abstract

Femtosecond-laser-assisted material restructuring employs extreme optical intensities to localize the ablation regions. To overcome the minimum feature size limit set by the wave nature of photons, there is a need for new approaches to tailored material processing at the nanoscale. Here, we report the formation of deeply-subwavelength features in silicon, enabled by localized laser-induced phase explosions in pre-fabricated silicon resonators. Using short trains of mid-infrared laser pulses, we demonstrate the controllable formation of high aspect ratio (>10:1) nanotrenches as narrow as ∼λ/80. The trench geometry is shown to be controlled by multiple parameters of the laser pulse train, such as the intensity and polarization of each laser pulse and their total number. Particle-in-cell simulations reveal localized heating of silicon beyond its boiling point and suggest its subsequent phase explosion on the nanoscale commensurate with the experimental data. The observed femtosecond-laser assisted nanostructuring of engineered microstructures (FLANEM) expands the nanofabrication toolbox and opens exciting opportunities for high-throughput optical methods of nanoscale structuring of solid materials.

Ultra-high-aspect-ratio structures through silicon using infrared laser pulses focused with axicon-lens doublets

“…More recently, Tokel et al interestingly demonstrated sub-surface 2D-confined nanochannel generation in c-Si by scanning micro-Bessel nanosecond laser beams at the vicinity of preformed structures [25]. While the nature of this pre-structure non-local seeding technique is associated with freedom limitations for 3D manufacturing applications, this represents an important advancement as it tends to translate in the bulk an important concept for nanoscale writing resolutions and exploited on surfaces [26].…”