Photoacoustic Techniques for Thermal Characterization

Photoacoustic techniques exploit the generation of acoustic waves by the periodic heating of a material induced by modulated light. When a sample absorbs photons, rapid local heating produces thermoelastic expansion or gas pressure fluctuations that emit sound waves. By analysing the amplitude and phase of these waves in either the frequency or time domain, one can determine key thermal parameters such as thermal diffusivity, thermal effusivity and thermal conductivity. These non‐contact methods are particularly well suited to thin films, polymers, semiconductors and layered composites, offering micrometre‐scale spatial resolution and sensitivity to subsurface properties. Advances in analytical modelling, inverse problem methodologies and data‐driven algorithms have extended the applicability of photoacoustic characterisation to systems with low diffusivity, complex internal structure or multiple thermal relaxation pathways. Such versatility underpins global efforts in microelectronics, energy materials, biomedical diagnostics and environmental sensing, where accurate thermal property measurements are critical for device performance and material reliability.

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Photoacoustic Techniques for Thermal Characterization publication trend

The graph below shows the total number of articles in photoacoustic techniques for thermal characterization across all publications each year (not limited to Nature Index journals).

Technical terms

Photoacoustic spectroscopy: A technique in which modulated light absorption induces acoustic waves that are detected to infer thermal and optical properties of a sample.

Thermal diffusivity: The rate at which heat spreads through a material, defined as thermal conductivity divided by volumetric heat capacity.

Thermal effusivity: A measure of a material’s ability to exchange heat with its surroundings, combining thermal conductivity and heat capacity.

Thermoelastic bending: Mechanical deformation of a solid due to non‐uniform thermal expansion following local heating.

Inverse problem: The mathematical process of inferring material properties from measured signals by solving equations that relate input stimuli to observed responses.

Fractional dual‐phase‐lag theory: A model of heat conduction that incorporates two time delays (phase lags) and fractional derivatives to describe non‐classical thermal transport behaviours.

References

1. Photoacoustic thermal characterization of low thermal diffusivity thin films. Photoacoustics (2021).
2. Photothermal Response for the Thermoelastic Bending Effect Considering Dissipating Effects by Means of Fractional Dual-Phase-Lag Theory. Fractal and Fractional (2023).
3. Photoacoustic Characterization of TiO2 Thin-Films Deposited on Silicon Substrate Using Neural Networks. Materials (2023).
4. Solution of Inverse Photoacoustic Problem for Semiconductors via Phase Neural Network. Mathematics (2024).