Giant‐Amplitude Coherent Acoustic Waves in Cuprous Oxide

Coherent acoustic waves in the gigahertz‐to‐terahertz regime offer powerful opportunities for nanoscale imaging and quantum technologies, yet their use in solids has been constrained by the intrinsically weak acoustic response to optical excitation, which typically yields transient reflectivity modulations usually below 10 −4 . Here we report that cuprous oxide (Cu 2 O) single crystals support efficient generation of coherent acoustic waves, with transient reflectivity modulations approaching 10 −2 . The pronounced response is consistent with a deformation‐potential‐dominated generation mechanism enabled by strong electron‐phonon coupling. In addition, the intrinsically low thermal conductivity and highly symmetric cubic structure of Cu 2 O are favorable for suppressing phonon dissipation and sustaining acoustic propagation. With this platform, we demonstrate coherent interference of acoustic waves using two‐pulse excitation and show that the resulting strain waves can map variations in interlayer coupling across a WS 2 /hBN van der Waals heterostructure with nanoscale sensitivity. These results establish Cu 2 O as an optoacoustic medium for coherent phonon engineering and suggest new opportunities for ultrafast acousto‐photonic imaging and control.