Confinement of acoustical vibrations in a semiconductor planar phonon cavity

TL;DR

This paper introduces a novel semiconductor phonon cavity that confines acoustical vibrations, demonstrated through Raman scattering experiments in GaAs/AlAs structures, with results matching theoretical models.

Contribution

It proposes and experimentally demonstrates a new type of phonon cavity in semiconductor superlattices for confining acoustic vibrations.

Findings

Successful confinement of acoustical phonons in semiconductor layered structures.

Raman spectra confirm the presence of confined phonon modes.

Experimental results align with photoelastic model calculations.

Abstract

Extending the idea of optical microcavities to sound waves, we propose a {\it phonon cavity} consisting of two semiconductor superlattices enclosing a spacer with thickness determined by the acoustic wavelength at the center of the first zone-center folded minigap. We show that acoustical phonons can be confined in these layered structures, and propose Raman experiments which are able to probe these novel excitations. The Raman experiments take profit of an optical microcavity scattering geometry that, through the forward-scattering contribution, gives access to the zone-center excitations. We report experimental results of Raman scattering in a structure based in GaAs/AlAs materials that demonstrate unambiguously the observation of phonon cavity confined acoustical vibrations. The experimental results compare precisely with photoelastic model calculations of the Raman spectra of the proposed phonon-cavity embedded optical microcavity.