Nanoscale Imaging of Ultrafast Light Coupling to Self-Organized Nanostructures

Abstract

In the course of laser-induced surface self-organization, an optical feedback mechanism is generally evoked as the main process driving the final rippled topography. To unravel the role of light and transient nanostructures in a multipulse irradiation regime, we use a high-resolved imaging technique, the photoemission electron microscopy. The pulse-topulse evolution of the inhomogeneous laser field distribution on a titanium surface nanostructured by a femtosecond laser is investigated at the nanoscale. Photoelectron imaging allows to separate the contributions of radiative and nonradiative scattered fields and to unveil the correlation between the nanocavity density and the quasi-periodic light absorption. The multipulse experimental observations are supported by electromagnetic calculations showing that the absorption of light on an evolving surface relief drives the selection of the final periodicity. The surface distribution of light absorption is influenced by surface topography that transiently adapts following the collective optical response of nanocavities, namely, the reinforcement of the dipole−dipole coupling as the nanocavity density increases. Mapping the evolution of the photoelectron emission sheds new light on the intricate mechanisms controlling the laser-induced surface self-organization features.

Laser-induced periodic surface structures: Arbitrary angles of incidence and polarization states

“…Comparing the spatial-domain images, the positions of the ridges and valleys of the LSFLs generated by a subsequent pulse is always aligned with those of the previous pulses, indicating a phase-locking mechanism that stabilize and amplifies the periodic structures. This is in consistent with experimental results utilizing high-resolution pulse-to-pulse imaging techniques [37,[69][70][71]. The type-g features gradually grow after the illumination of three pulses.…”

“…In addition to the ability to model arbitrary polarization states and incidence angles, further advantages of the FDTD approach over the efficacy theory include the ability to model topography-driven interpulse feedback effects [11,39] and to study surface topography in the spatial domain. The interpulse feedback mechanism has been shown as the main process driving the final rippled topography [37,[69][70][71]. The interpulse feedback effect here is taken into account by the socalled holographic ablation model (HAM) first introduced by Skolski et al [11]: After the simulation of the first pulse, the topography of the sample is updated according to the calculated energy absorption, implying a change of material permittivity to 1 (material removal) when the local energy density exceeds the ablation criterion.…”

Self‐Aligned Laser‐Induced Periodic Surface Structures for Large‐Area Controllable Nanopatterning

“…When ultrafast laser irradiates into a strongly absorbing material surface with pregenerated LIPSS sequentially, we discover an attractive SPPs enhancement called h‐MOE between every tip of adjacent preproduced ripples, which can redistribute the periodic energy deposition for new LIPSS generation ( Figure a). [ 7,28 ]…”

Ultrafast dynamics of subwavelength periodic ripples induced by single femtosecond pulse: from noble to common metals

“…The experimental and theoretical results support the view that the SPP excitations play a very important role in the formation of periodic ripples on the surfaces of metals. The developed SPP model, including the effects of hotelectron localization and inter-band transitions, is expected to be a general model for understanding the formation of subwavelength ripples on metal surfaces induced by femtosecond laser pulses [95].…”