Generation of nonthermal GHz phonons (pump-BLS)

The nonthermal conditions in electronic and photonic devices can drastically change materials' mechanical and "thermal" properties. Such conditions can be accessed with pumped-BLS, where ultrashort photoexcitation amplifies acoustic signals and brings them to nonthermal states. Most naturally, pumped-BLS studies ultrathin semiconductors and metal-semiconductor heterojunctions, but future works aim for acoustic diodes, topological phononics, and acoustic Anderson localization.

Figure: All-optical-based method for enhancing and controlling the spectra of spatially confined gigahertz acoustic signals. The femtosecond pulses are focused on a semiconducting nanomembrane (260 nm Si). The continuous wave (CW) laser light (532 nm) is inelastically scattered by both photoexcited and thermal phonons, and the spectrum is recorded by Brillouin light spectroscopy (BLS) at backscattering.
References:

Frequency-domain study of nonthermal gigahertz phonons reveals Fano coupling to charge carriers, Vasileiadis, T., Zhang, H., Wang, H., Bonn, M., Fytas, G., Graczykowski, B. Science Advances 6(51), eabd4540 (2020),
Fano meets Stokes: Four-order-of-magnitude enhancement of asymmetric Brillouin light scattering spectra, Białek, R., Vasileiadis, T., Pochylski, M., Graczykowski, B. Photoacoustics 30, 100478 (2023),
Progress and perspectives on phononic crystals, Vasileiadis, T., Varghese, J., Babacic, V., Gomis-Bresco, J., Navarro Urrios, D., Graczykowski, B. Journal of Applied Physics 131(18), 180901(2022),
Phonon transport in the gigahertz to terahertz range: Confinement, topology, and second sound, Vasileiadis, T., Reparaz, J.S., Graczykowski, B. Journal of Applied Physics 131(18), 180901 (2022).

Ways to reach us