Numerical study of laser micro- and nano-processing of nanocomposite porous materials

TL;DR

This paper presents numerical simulations of laser interactions with porous materials, enabling controlled micro- and nano-structuring, including insights into nanoparticle growth and formation of nanostructures in porous glass and TiO2 films.

Contribution

It introduces detailed multi-physical models for laser processing of porous materials, advancing understanding of nanoparticle growth and nanostructure formation during laser micro- and nano-processing.

Findings

Controlled laser micro-machining of SiO2 correlates with experimental dimensions.

Laser writing speed influences Ag nanoparticle size and temperature.

Pulsed laser processing can generate surface grooves and nanogratings.

Abstract

This thesis is focused on numerical simulations of the laser interaction with porous materials. A possibility of well-controlled processing is particularly important for the laser based micro-structuring of porous glass and nano-machining of semiconducting porous materials in the presence of metallic nanoparticles. To understand the periodic micro-void structures produced inside porous glass by femtosecond laser pulses, a detailed numerical thermodynamic analysis was performed. The calculation results show the possibility to control laser micro-machining in volume of SiO2. The obtained characteristic dimensions of the structures correlate with the experimental results. Comparing to the porous glass, the mesoporous TiO2 films loaded by Ag ions and nanoparticles support localized plasmon resonances. To identify the optimum parameters of the continuous-wave laser, a multi-physical model considering Ag nanoparticle growth, photo-oxidation, reduction was developed. The performed simulations show that the laser writing speed controls the Ag nanoparticles size. The thermally activated fast growth followed by the photo-oxidation was found to be the main reason for the writing speed-dependent size-change and temperature rises. Writing of mesoporous TiO2 films loaded with Ag nanoparticles by a pulsed laser is, furthermore, promising to provide additional possibilities in the generation of two kinds of nanostructures: laser-induced periodic surface grooves and Ag nanogratingsinside the TiO2 film. To better understand the effects of a pulsed laser, two multi-pulses models are developed to simulate the Ag nanoparticle growth. The obtained results provided new insights into laser micro-processing of porous material and better laser controlling over nanostructuring in porous semiconducting films loaded with metallic nanoparticles.