Researchers: Matteo Fisicaro, Thomas Steenbergen

Surface acoustic waves (SAWs) are mechanical waves that travel on the surface of a material and can be controlled down to the quantum level. They are commonly excited and detected using interdigital transducers (IDTs) consisting of two interleaved comb-shaped metal electrodes on a piezoelectric substrate. We show here the nanofabrication of a GHz IDT device on a GaAs substrate, and its characterization, both electrically and optically by means of interferometric measurements. The optical measurement of the generated SAWs is the first step towards integrating the IDT device in our custom built open-access optical microcavity which is compatible with a closed-cycle cryostat. This novel platform can be used in the future for quantum acoustics experiments, where in principle even a single SAW phonon can be detected via the quantum-confined Stark shift it induces in a single quantum dot.

How to make a double-slit experiment for GHz surface acoustic waves? We used a focussed ion beam to mill tiny grooves into the surface of a GaAs crystal, launched the waves with an interdigital transducer and used our imaging instrument (below) to image the waves on the surface! Things are more complex than for light in free space, due to the anisotropic wave propagation in GaAs.

Caren Huygelen has written a popular article about this: https://www.universiteitleiden.nl/en/news/2025/11/how-sound-and-light-act-alike---and-not---at-the-smallest-scale

Our publication: Young's double-slit experiment with anisotropic GHz surface acoustic waves on gallium arsenide, Thomas Steenbergen, Matteo Fisicaro, Krystian Czerniak, Matthijs Rog, Kaveh Lahabi, Wolfgang Löffler
Opt. Lett. 50, 6385 (2025), arXiv:2507.10117

By defocussing our surface acoustic wave imaging instrument, we found the Talbot effect upon a dynamical grating which oscillates at GHz frequency! Apart from fundamental interest, this might be useful for high-speed optical modulation.

Observation of the Talbot effect from a surface acoustic wave dynamic grating
M. Fisicaro, Y. C. Doedes, T. A. Steenbergen, M. P. van Exter, W. Löffler
Phys. Rev. A 111, 043513 (2025), arXiv:2409.11161

We have developed an instrument to image micrometer-scale surface acoustic waves over millimeters, with phase-sensitive lock-in detection:

Imaging transverse modes in a gigahertz surface-acoustic-wave cavity
M. Fisicaro, T. A. Steenbergen, Y. C. Doedes, K. Heeck, W. Löffler
Phys. Rev. Applied 23, 014032 (2025), ArXiv:2408.11630