Nano- and Micro- Acoustic Waves Generated by Pulsed Lasers and Applications in Materials Science

Overview

Laser-generated ultrasound is a powerful tool for material characterization and modification. Our research group develops and applies an integrated methodology combining high-precision experiments and advanced computational simulations to study these phenomena.

Experimental Approach

We employ pump-probe interferometry techniques to generate and simultaneously record the evolution of SAWs. A “pump” pulse excites the sample, while a second, time-delayed “probe” pulse records the surface deformation via Michelson interferometry. This setup enables:

• High resolution: The method offers lateral resolution ~1 μm and out-of-plane resolution ~1 nm, allowing real-time monitoring of wave propagation.
• Brillouin detection: In thin films, Brillouin oscillations in the reflectivity signal provide information on the amplitude and velocity of acoustic pulses within the substrate.
• Use of different laser sources for pump and probe pulses.

Computational Approach

To understand and predict material behavior, we develop advanced computational models using the Finite Element Method (FEM). These models simulate:

• The propagation of acoustic waves, considering non-linear phenomena, plastic deformation, and phase changes (melting, ablation).
• The interaction of waves with inhomogeneities (surface cracks, material boundaries).
• Stress accumulation and the formation of Laser-Induced Periodic Surface Structures (LIPSS).
• In the case of fs pulse excitation, the simulations incorporate the Two-Temperature Model (TTM), which describes the initial excitation and heating of electrons, as well as the energy transfer to the lattice via electron-phonon coupling.

Applications and Key Findings

Transducer Material Evaluation: We compared the performance of thin Ta, Ti, and Au films. Ta emerges as an excellent transducer, generating stronger acoustic strains in Si compared to Ti, due to its high Young’s modulus and favorable elastic behavior.

Non-Destructive Testing: We demonstrated that fs-laser-generated SAWs have a shallow penetration depth (<15 μm) and are ideal for detecting surface defects (e.g., cracks), in contrast to ns-laser-generated SAWs which probe deeper.

LIPSS Formation: We studied that the formation of periodic surface structures (LIPSS) can be triggered by the interference of mechanical waves reflected from boundaries (e.g., previous craters). The radiation penetration depth and light polarization play a crucial role in the morphology and regularity of the structures.

Publications

Kaleris, K., Kaniolakis-Kaloudis, E., Kaselouris, E., Kosma, K., Gagaoudakis, E., Binas, V., Petraklis, S., Dimitriou, V., Bakarezos, M., Tatarakis, M., Papadogiannis, N.A. (2023). Efficient ultrafast photoacoustic transduction on Tantalum thin films. Applied Physics A, 129, 550. https://doi.org/10.1007/s00339-023-06797-6 

Papadaki, H., Mirza, I., Bulgakova, N.M., Kaselouris, E., Dimitriou, V. (2025). Thermomechanical Study of Periodic Surface Structuring on Silicon Wafers via Picosecond Laser Pulses. Materials, 18(23), 5506. https://doi.org/10.3390/ma18245506

Mirza, I., Sládek, J., Levy, Y., Bulgakov, A.V., Dimitriou, V., Papadaki, H., Kaselouris, E., Gečys, P., Račiukaitis, G., Bulgakova, N.M. (2025). Coherence effects in LIPSS formation on silicon wafers upon picosecond laser pulse irradiations. Journal of Physics D: Applied Physics, 58(8), 085307. https://doi.org/10.1088/1361-6463/ad9d51

Kosma, K., Kaleris, K., Kaselouris, E., Kaniolakis-Kaloudis, E., Petrakis, S., Orphanos, Y., Gagaoudakis, E., Binas, V., Bakarezos, E., Tatarakis, M., Dimitriou, V., Papadogiannis, N.A. (2023). Pump-probe reflectivity studies of ultrashort laser-induced acousto-mechanical strains in ZnO films. Applied Physics A, 129, 597. https://doi.org/10.1007/s00339-023-06837-1

Papadaki, H., Kaselouris, E., Bakarezos, M., Tatarakis, M., Papadogiannis, N.A., Dimitriou, V. (2023). A Computational Study of Solid Si Target Dynamics under Pulsed Laser Irradiation from Elastic to Melting Regime. Computation, 11(12), 240. https://doi.org/10.3390/computation11120240

Orphanos, Y., Kosma, K., Kaselouris, E., Vainos, N., Dimitriou, V., Bakarezos, M., Tatarakis, M., Papadogiannis, N.A. (2019). Integrated nanosecond laser full-field imaging for femtosecond laser-generated surface acoustic waves in metal film-glass substrate multilayer materials. Applied Physics A, 125, 269. https://doi.org/10.1007/s00339-019-2552-6

Bakarezos, M., Tzanaki, E., Petraki, S., Tsibidis, G., Loukakos, P.A., Dimitriou, V., Kosmidis, C., Tatarakis, M., Papadogiannis, N.A. (2018). Ultrafast laser pulse chirp effects on laser-generated nanoacoustic strains in Silicon. Ultrasonics, 86, 14-19. https://doi.org/10.1016/j.ultras.2018.01.008

Tzianaki, E., Bakarezos, M., Tsibidis, G.D., Orphanos, Y., Loukakos, P.A., Kosmidis, C., Patsalas, P., Tatarakis, M., Papadogiannis, N.A. (2015). High acoustic strains in Si through ultrafast laser excitation of Ti thin-film transducers. Optics Express, 23(13), 17191-17204. https://doi.org/10.1364/OE.23.017191

Kaselouris, E., Nikolos, I.K., Orphanos, Y., Bakarezos, E., Papadogiannis, N.A., Tatarakis, M., Dimitriou, V. (2016). Elastoplastic study of nanosecond-pulsed laser interaction with metallic films using 3D multiphysics fem modeling. International Journal of Damage Mechanics, 25(1), 42-55. https://doi.org/10.1177/1056789515576553

Dimitriou, V., Kaselouris, E., Orphanos, Y., Bakarezos, M., Vainos, N., Nikolos, I.K., Tatarakis, M., Papadogiannis, N.A. (2015). The thermo-mechanical behavior of thin metal films under nanosecond laser pulse excitation above the thermoelastic regime. Applied Physics A, 118, 739-748. https://doi.org/10.1007/s00339-014-8792-6