Resonance of terahertz phonons in an acoustic nanocavity

Abstract

We show the resonant behavior of ∼0.5-THz longitudinal acoustic (LA) phonons in an acoustic nanocavity of thickness ∼28 nm sandwiched between two GaAs/AlAs superlattices (SLs). One of the SLs, upon excitation with an ultrafast optical pulse, acts as a source of coherent LA phonons. These phonons, generated outside the cavity, resonantly drive the cavity mode. The phonon dynamics can be modeled using a driven-damped harmonic oscillator. The confinement and enhancement of phonons in the acoustic nanocavity opens up possibilities in the field of nanophononics.