Séminaire

Mardi 31 Mai 2022 à 11h00.

Advances in Photoacoustic and Photothermal Science and Techniques: a route for NDT from Macro to Nanoscale

'' ATTENTION salle inhabituelle: Salle de réunion KASTLER 13-001
One of the most challenging problems in nanomaterials research is their accurate characterization, which is fundamental for the efficient use of these technologically promising materials. Absolute absorption, quantum efficiency, thermal diffusivity, and the elastic constants are important parameters for photonic applications. Although the conventional absorption or emission techniques can provide the absorption coefficient, the determination of the absolute absorption is not a trivial measurement due to the presence of scattered light. On the contrary Photoacoustic (PAS) and Photothermal Spectroscopy are very sensitive techniques, immune to scattered or reflected light, and easy to be used to measure the absolute absorption in many different wavelength ranges.
In this summary we review recent advances in the methodology of PAS and its novel applications. In particular we highlight some works done to detect circular dichroism of intrinsic chiral materials [1] as well as extrinsic pseudo-chiral metasurfaces [2], showing how PAS can be applied to measure the selective absorption of circularly polarized light depending on the orientation of the metasurface. PAS has been also applied to measure the resonant absorption peaks related to the guided modes of GaAs-based NW on Si in the VIS/IR range [3, 4]. In disordered media PAS is confirmed to be the most appropriate technique to determine separately the absorption and the scattering coefficients allowing to determine the size of both metallic (AgNP) [5], or semiconductor nanospheres (ZnO) [6, 7], or clusters of nanospheres bridged by the ligands [5, 8], in contrast to nanolayered samples [9, 10].
We also underline some applications of photothermal radiometry (PTR) used to localize the internal heat sources where the pump light is absorbed, and to measure the effective thermal diffusivity. The modulation frequency obtained by an acousto-optical modulator ranges from 1 Hz up to 100 kHz, allowing the improvement of the thermal resolution from millimiter to submicron range [11].
The talk summarizes several research topics and works done in collaboration with the Italian National Research Council, the University of Bath, the University of Dayton, the Tampere University of Technology, ICMM – CSIC in Madrid, the IOFFE Institute in S.Petersburg, and the Hokkaido University in Sapporo.

References
[1] Benedetti, A., et al. Scientific Reports, 7, 5257 (2017).
[2] R. Li Voti, et al. Applied Sciences, 12, 1109, (2022)
[3] Leahu, G. et al. Scientific Reports, 7, 2833 (2017).
[4] Petronijevic, E, et al. Int J Thermophys, 39, 45 (2018).
[5] Li Voti R. et al. Nanoscale Advances 3, Issue 16, Pages 4692 - 470121 (2021)
[6] Lamastra, F.R., Nanotechnology 28, 375704 (2017).
[7] Lamastra, F.R., et al, Int J Thermophys, 39, 110, (2018).
[8] I. Fratoddi, at al., Journal of Physical Chemistry C 121, 18110 (2017).
[9] Cesarini, G., et al Physica Status Solidi (C) 13, 998 (2016).
[10] Osewski, P., et al. Adv. Optical Mater. 1901617 (2020).
[11] G. Leahu, et al Int J Thermophys, 36: pp.1349–1357 (2015).
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