Local activation of surface and hybrid acoustic waves in optical microwires

Elastic vibrations in subwavelength structures have gained importance recently in fundamental light-matter studies and various optoacoustic applications. Existing techniques have revealed the presence of distinct acoustic resonances inside silica microwires yet remain unable to individually localize them. Here, we locally activate distinct classes of acoustic resonances inside a tapered fiber using a phase-correlation distributed Brillouin method. Experimental results verify the presence of surface and hybrid acoustic waves at distinct fiber locations and demonstrate, to the best of our knowledge, the first distributed surface acoustic wave measurement. This technique is important for understanding properties of optoacoustic interactions and enabling designs of novel optomechanical devices.