Engineering phononic cavities: ultrafast phonon and carrier dynamics

Materials having tailor-made electronic and phononic properties are vital for energy conversion, thermal management and novel sub-THz applications. To this end, we have demonstrated phonon cavities designed to operate at 96GHz with parabolic, quartic and linear 1D phonon potentials using GaAs/AlAs superlattices. Ultrafast vibrational spectroscopy shows long lived coherent acoustic phonon modes confined by the cavity at room temperature. Moreover, time resolved photoluminescence characterization showed a slow carrier energy loss rate compared to a DBR sample fabricated to exhibit linear phonon dispersion without confinement. These results can help develop new device architectures for applications where phonons either need to be confined or efficiently guided.