Optomechanics with levitated nanodiamonds

Thesis (Ph. D.)--University of Rochester. Department of Physics and Astronomy, 2015.Free-space optical levitation of massive objects marries the physics and experimental techniques from the mature field of optical tweezers, with the relatively new and expanding field of optomechanics. This thesis details the design, construction, and characterization of an apparatus which can optically levitate and manipulate the dynamics of dielectric nanoparticles in a vacuum environment. It further describes work toward the development of a versatile spin-optomechanics platform based on optically levitated nanodiamonds. The apparatus relies on the optical gradient force imparted to the particle by a single, tightly-focused Gaussian laser beam which confines the particle in three dimensions. Near the laser focus, the optical potential well is approximately parabolic, giving rise to harmonic motion in vacuum. A parametric feedback signal generated from real-time measurements of the particle position modulates the trapping laser intensity. This allows optomechanical damping or excitation of the motion. We characterize the optomechanical cooling performance, and directly compare it to a similar, previously reported system. Finally, we use the apparatus to conduct preliminary optomechanics experiments with nanodiamonds which contain either individual, or ensembles of, optically addressable spins in the form of nitrogen-vacancy defect centers. We observe fluorescence from the defects in nanodiamonds levitated at atmospheric pressure and in low vacuum. In vacuum, we demonstrate the ability to optomechanically modulate the fluorescence rates, and resonantly drive spin transitions. This proof-of-principle work suggests levitated nanodiamonds to be suitable platforms for future spin-optomechanical work