Coherent Acoustic Wave Techniques in Advanced Materials

Coherent acoustic wave techniques harness ultrafast laser pulses to generate and detect high-frequency acoustic phonons in solids, enabling non-invasive probing of mechanical, structural and opto-acoustic properties at nanometre to micrometre scales. By synchronising pump and probe pulses on picosecond timescales, these methods track the propagation of strain pulses through layered films, crystals, polymers and biological specimens. The acoustic wavelength, determined by the material’s sound velocity and the excitation frequency, defines the spatial resolution, which can surpass optical diffraction limits. Time-domain Brillouin scattering and picosecond ultrasonics extract depth‐resolved elastic moduli, interfacial adhesion characteristics and viscoelastic responses, while acousto-optic interactions enable ultrafast modulation of light in photonic devices. Applications span subsurface nanometrology, three-dimensional imaging of grain microstructure in ceramics, high-resolution cell morphology mapping, characterisation of semiconductor heterostructures and the development of next-generation acousto-optic mode converters. The global significance of these techniques lies in their capacity to unify mechanical, optical and electronic interrogations within a single platform, driving advances in materials design, biomedical diagnostics and ultrafast photonics.

Research from Nature Portfolio

Recent studies have extended coherent acoustic imaging to energy materials by combining pump–probe acoustics with polarisation-sensitive detection to map grain orientations in ceria ceramics. Depth profiles of acoustic echoes reveal individual crystallite boundaries and local anisotropy, offering a multimodal route to correlate microstructure with electrochemical performance. In parallel, ultrafast coherent phonons have been employed to reconstruct three-dimensional cell morphology without labels. Resonance harmonics of gigahertz acoustic waves yield out-of-plane resolution down to a tenth of the optical wavelength, accurately imaging sub-cellular features and validating results against atomic force microscopy. Foundational work on all-optical mode conversion in ferroelectric crystals demonstrates the manipulation of light polarisation with gigahertz phonons, opening avenues for acousto-optic multiplexing in photonic circuits. These developments underscore the versatility of coherent acoustics across inorganic, organic and biological systems.

Coherent Acoustic Wave Techniques in Advanced Materials publication trend

The graph below shows the total number of articles in coherent acoustic wave techniques in advanced materials across all publications each year (not limited to Nature Index journals).

Technical terms

Coherent acoustic phonon: A synchronised lattice vibration generated and detected by ultrafast optical pulses, used to probe mechanical properties at very high frequencies.

Time-domain Brillouin scattering: A pump–probe technique that measures periodic modulations in reflected or transmitted light caused by propagating acoustic waves to extract elastic moduli and refractive indices.

Picosecond ultrasonics: A method employing femtosecond or picosecond laser pulses to generate strain pulses in a material and monitor their reflections for depth-resolved mechanical characterisation.

Acousto-optic interaction: The modulation of light by an acoustic wave through changes in refractive index, enabling ultrafast light control and signal processing.

Pump–probe spectroscopy: A pair of time-delayed laser pulses where the pump excites dynamic processes and the probe interrogates the resulting changes in the sample over ultrafast timescales.

References

1. Imaging grain microstructure in a model ceramic energy material with optically generated coherent acoustic phonons. Nature Communications (2020).
2. Remote imaging of single cell 3D morphology with ultrafast coherent phonons and their resonance harmonics. Scientific Reports (2019).
3. Ultrafast acousto-optic mode conversion in optically birefringent ferroelectrics. Nature Communications (2016).
4. Characterization of thin-film adhesion and phonon lifetimes in Al/Si membranes by picosecond ultrasonics. New Journal of Physics (2017).
5. Viscoelastic properties and efficient acoustic damping in confined polymer nano-layers at GHz frequencies. Scientific Reports (2016).
6. Picosecond ultrasonics with a free-running dual-comb laser.. Optics Express (2021).
7. Phonon imaging in 3D with a fibre probe. Light: Science & Applications (2021).
8. Detection of Hidden Gratings through Multilayer Nanostructures Using Light and Sound. Physical Review Applied (2020).