PT Symmetry, induced mechanical lasing and tunable force sensing in a coupled-mode optically levitated nanoparticle

Abstract: We theoretically investigate PT symmetry, induced mechanical lasing and force sensing in an optically levitated nanoparticle with coupled oscillation modes. The coupling in the levitated system is created by the modulation of an asymmetric optical potential in the plane transverse to the beam trapping the nanoparticle. We show that such a coupling can lead to PT-symmetric mechanical behavior for experimentally realistic parameters. Further, by examining the phonon dynamics and the second-order coherence of the nanoparticle modes, we determine that induced mechanical lasing is also possible. Finally, we demonstrate that tunable ultra-sensitive force sensing can be engineered in the system. Our studies represent an advance in the fields of coherent manipulation of coupled degrees of freedom of levitated mechanical oscillators and their application for sensing.