Enhanced plasmonic coloring of silver and formation of large laser-induced periodic surface structures using multi-burst picosecond pulses

TL;DR

This study demonstrates that using closely spaced laser bursts on silver enhances plasmonic coloring by increasing color saturation and lightness range, while also creating large periodic surface structures, with underlying mechanisms supported by simulations.

Contribution

The paper introduces a burst mode laser technique that significantly improves plasmonic coloring and surface structuring of silver compared to traditional methods.

Findings

Burst mode increases Chroma by ~50% and broadens lightness by ~60%.

Large laser-induced periodic surface structures (LLIPSS) are formed, being 10 times the laser wavelength.

Simulations reveal increased electron-phonon coupling and HSFL structures contribute to improved color properties.

Abstract

We report on the creation of angle-independent colors on silver using closely time-spaced laser bursts. The use of burst mode, compared to traditional non-burst is shown to increase the Chroma (color saturation) by ~50% and to broaden the lightness range by up to ~60%. Scanning electron microscope analysis of the surfaces created using burst mode, reveal the creation of 3 distinct sets of laser induced periodic surface structures (LIPSS): low spatial frequency LIPSS (LSFL), high spatial frequency LIPSS (HSFL) and large laser-induced periodic surface structures (LLIPSS) that are 10 times the laser wavelength and parallel to the laser polarization. Nanoparticles are responsible for each plasmonic color and their distributions are observed to be similar for both burst and non-burst modes, indicating that the underlying structures (i.e. LIPSSs) are responsible for the increased Chroma and Lightness. Two-temperature model simulations of silver irradiated by laser bursts show significant increase in the electron-phonon coupling coefficient which is crucial for the creation of well-defined ripple structures. Finite difference time domain (FDTD) simulations of the colored surfaces show the increase in Chroma to be attributable to the HSFL arising in burst mode.