All-optical dynamic analysis of the photothermal and photoacoustic response of a microcantilever by laser Doppler vibrometry

Yang Liu; Tommaso Seresini; Jun-Yan Liu; Liwang Liu; Fei Wang; Yang Wang; Christ Glorieux

doi:10.1016/j.pacs.2021.100299

All-optical dynamic analysis of the photothermal and photoacoustic response of a microcantilever by laser Doppler vibrometry

Photoacoustics. 2021 Aug 31:24:100299. doi: 10.1016/j.pacs.2021.100299. eCollection 2021 Dec.

Authors

Yang Liu^{1

2

3}, Tommaso Seresini¹, Jun-Yan Liu^{2

3}, Liwang Liu¹, Fei Wang^{2

3}, Yang Wang^{2

3}, Christ Glorieux¹

Affiliations

¹ Laboratory for Soft Matter and Biophysics, Department of Physics and Astronomy, KU Leuven, Leuven, B-3001, Belgium.
² State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, 150001, China.
³ School of Mechatronics Engineering, Harbin Institute of Technology, Harbin, 150001, China.

Abstract

Light absorption induced thermoelastic and photoacoustic excitation, combined with laser Doppler vibrometry, was utilized to analyze the dynamic mechanical behavior of a microcantilever. The measured frequency response, modal shapes, and acoustic coupling effects were interpreted in the framework of a simple Bernouilli-Euler model and quantitative 3D finite element method (FEM) analysis. Three opto-mechanical generation mechanisms, each initiated by modulated optical absorption and heating, were identified both by an analytical and finite element model. In decreasing order of importance, optically induced cantilever bending is found to be caused by: (i) differences in photoacoustically induced pressure oscillations in the air adjacent to the illuminated and dark side of the cantilever, resulting from heat transfer from the illuminated cantilever to the nearby air, acting as a volume velocity piston, and (ii) thermoelastic stresses accompanying temperature and thermal expansion gradients in the cantilever, (iii) photoacoustically induced pressure oscillations in the air adjacent to the illuminated cantilever holder and frame.

Keywords: Cantilever; Modal analysis; Mode shape; Photoacoustic; Photothermal.