Coherent control of acoustic phonons in a silica fiber using a multi-GHz optical frequency comb

Multi-gigahertz mechanical vibrations stemming from interactions between light fields and matter, also known as acoustic phonons, have long been a subject of study. In recent years, specially designed functional devices have been developed to enhance the light-matter interaction strength, since the excitation of acoustic phonons by a continuous wave laser alone is insufficient. However, with such structure-dependent enhancements, the strength of the interaction cannot be aptly and instantly controlled. We propose a new technique to control the effective interaction strength, which is not via the material structure in the spatial domain, as with the above-mentioned specially designed functional devices, but through the structure of light in the time domain. Here we show the effective excitation and coherent control of acoustic phonons in a single-mode fiber using an optical frequency comb by tailoring the optical pulse train. We believe this work represents an important step towards "comb-matter interactions."