Temporal superoscillations of subterahertz coherent acoustic phonons

We observe coherent acoustic phonon superoscillations at subterahertz frequencies. The superoscillations result from the interference of optically excited coherent longitudinal acoustic phonon modes in a GaAs/AlGaAs superlattice. The superoscillations are seen in local temporal regions and their frequency is up to 60% larger than the highest-frequency excited and detected phonon mode. Such superoscillatory phonon pulses may potentially be used for high-resolution acoustic measurement in strong scattering media.