An optical tweezer phonon laser

Phonon lasers are mechanical analogues of the ubiquitous optical laser and have been realized in a variety of contexts(1-12). However, no such demonstration exists for mesoscopic levitated optomechanical systems, which are emerging as important platforms for conducting fundamental tests of quantum mechanics(13-15) and gravity(16), as well as for developing sensing modalities that couple mechanical motion to electron spin(17-20) and charge(21). Inspired by the pioneering work of Arthur Ashkin on optical tweezers(22,23), we introduce a mesoscopic, frequency-tunable phonon laser based on the centre-of-mass oscillation of a silica nanosphere levitated in an optical tweezer under vacuum. Unlike previous levitated realizations, our scheme is general enough to be used on single electrons, liquid droplets or even small biological organisms(24). Our device thus provides a pathway for a coherent source of phonons on the mesoscale that can be applied to both fundamental problems in quantum mechanics as well as tasks of precision metrology(25-27).