We report pump-probe time resolved reflectivity experiments in a hybrid air–Ni metal–${\mathrm{BaTiO}}_3/{\mathrm{SrTiO}}_3$ oxide mirror phonon cavity. We demonstrate that the generated coherent acoustic phonon spectra of the impulsively excited metallic film can be inhibited or enhanced in the phonon cavity with respect to a Ni film directly grown on a ${\mathrm{SrTiO}}_3$ substrate. The experiments are compared with simulations that highlight the role of the phonon density of states in the coherent acoustic emission, extending concepts at the base of the optical Purcell effect to the field of phononics.

• Received 20 November 2009

DOI:https://doi.org/10.1103/PhysRevLett.104.187402