Nanometer-thick multilayer structures, characterized by contrasts in elastic properties, present promising avenues for engineering and manipulating acoustic phonons at the nanoscale. Semiconductor nano-acoustic cavities, particularly those based on Distributed Bragg Reflectors (DBRs), have demonstrated unique capabilities in simultaneously confining light and acoustic phonons. This dual confinement enhances phononic fields, making these structures attractive for ultra-high-frequency applications and as platforms for simulating solid-state systems[1].

In this study, we further explore hybrid nanostructures that are potentially tunable and responsive to  changes in elastic properties induced by external stimuli such as temperature, humidity, and electric fields. Building upon our theoretical simulations [2,3], our experimental investigation focuses on the dynamics of acoustic phonons in the frequency range of 5–500 GHz, using near-infrared pump-probe ultrafast transient reflectivity techniques. The materials studied include mesoporous thin-films, YBCO/STO multilayers, GaAs/AlAs DBRs, and other responsive materials such as vanadium oxide.

Our experimental findings pave the way for developing nanoacoustic sensing technologies and reconfigurable optoacoustic nanodevices.

[1] Priya, E.R. Cardozo de Oliveira, N.D. Lanzillotti-Kimura, Perspectives on high-frequency nanomechanics, nanoacoustics, and nanophononics, Appl Phys Lett. 122 (2023). https://doi.org/10.1063/5.0142925.

[2] E.R. Cardozo de Oliveira, P. Vensaus, G. J. A. A. Soler-Illia, and N. D. Lanzillotti-Kimura, Design of cost-effective environment-responsive nanoacoustic devices based on mesoporous thin films, Opt. Mater. Express 13 (2023). https://doi.org/10.1364/OME.504926.

[3] K. Papatryfonos, E.R.C. de Oliveira, N.D. Lanzillotti-Kimura, Effects of surface roughness and top layer thickness on the performance of Fabry-Perot cavities and responsive open resonators based on distributed Bragg reflectors, (2023). http://arxiv.org/abs/2309.13649.