Ripplon Laser

Energy exchange between light and sound was first suggested by Brillouin in 1922. After Townes established the phonon maser theory, coherent generation of intense hypersonic waves was observed together with stimulated Brillouin Scattering. Here we repeat these experiments, but with capillary-waves that are unique to the liquid phase of matter and relates to attraction between intimate fluid particles. We fabricate resonators that co-host capillary and opticalmodes, control it to operates at its non resolved sideband, and observe stimulated capillary scattering and coherent excitation of capillary resonances at kHz rates (that one can hear in audio files recorded by us). By exchanging energy between electromagnetic and capillary waves, we bridge interfacial tension phenomena at the liquid phase boundary to optics, and might impact optofluidics by allowing optical control, interrogation and cooling of water waves.