Temporal evolution of refractive index induced by short laser pulses accounting for both photoacoustic and photothermal effects

Xia, Z., Ni, B., Hou, R., Zhang, Y., Hou, L. , Hou, J. J., Marsh, J. H. , Liu, X. and Xiong, J. (2022) Temporal evolution of refractive index induced by short laser pulses accounting for both photoacoustic and photothermal effects. Applied Sciences, 12(12), 6256. (doi: 10.3390/app12126256)

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Materials such as silicon, copper, gold, and aluminum exhibit strong absorption and scattering characterization under short-pulsed laser irradiation. Due to the photoelastic effect and thermoelastic relaxation, the focal area may induce a local modulation in the refractive index, which can be detected with the intensity reflection coefficient perturbation. Normally, the thermal effect causes a weak refractive index change and is negligible, compared with the pressure-induced effect in most photoacoustic analytical systems. In this study, we present a theoretical model with the whole process of absorbed energy conversion analysis for the refractive index perturbation induced by both thermal effect and photoacoustic pressure. In this model, data analysis was carried out on the transformation of the energy absorbed by the sample into heat and stress. To prove the feasibility of this model, numerical simulation was performed for the photothermal and photoacoustic effects under different incident intensities using the finite element method. Experiment results on silicon and carbon fiber verified that the refractive index change induced by the photothermal effect can be detected and be incorporated with pressure-induced refractive index change. The simulation results showed very good agreement with the results of the experiments. The main aim of this study was to further understand the absorption and conversion process of short-pulsed light energy and the resulting photothermal and photoacoustic effects.

Item Type:Articles
Additional Information:Funding: This research was funded by the National Major Scientific Instruments and Equipment Development Project, Grant No. 61827814; Beijing Natural Science Foundation, Grant No. Z190018; the Fundamental Research Funds for the Central Universities, Grant No. 30920010011; and the Ministry of Education collaborative project (B17023). This research was also supported by the UK Engineering and Physical Sciences Research Council (Grant EP/R042578/1).
Glasgow Author(s) Enlighten ID:Hou, Dr Lianping and Marsh, Professor John
Authors: Xia, Z., Ni, B., Hou, R., Zhang, Y., Hou, L., Hou, J. J., Marsh, J. H., Liu, X., and Xiong, J.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
Journal Name:Applied Sciences
ISSN (Online):2076-3417
Published Online:20 June 2022
Copyright Holders:Copyright © 2022 by the authors
First Published:First published in Applied Sciences 12(12): 6256
Publisher Policy:Reproduced under a Creative Commons licence

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
302617Optically controlled THz phased array antennasJohn MarshEngineering and Physical Sciences Research Council (EPSRC)EP/R042578/1ENG - Electronics & Nanoscale Engineering