Abstract
Coupling between mesoscopic particles levitated in vacuum is a prerequisite for the realization of a large-scale array of particles in an underdamped environment as well as potential studies at the classical–quantum interface. Here, we demonstrate for the first time, to the best of our knowledge, optical binding between two rotating microparticles mediated by light scattering in vacuum. We investigate autocorrelations between the two normal modes of oscillation determined by the center-of-mass and the relative positions of the two-particle system. The inter-particle coupling, as a consequence of optical binding, removes the degeneracy of the normal mode frequencies, which is in good agreement with theory. We further demonstrate that the optically bound array of rotating microparticles retains their optical coupling during gyroscopic cooling, and exhibits cooperative motion whose center-of-mass is stabilized.
Highlights
A central theme in levitated optomechanics is the trapping and control over all the degrees of freedom of mesoscopic particles levitated in vacuum
While the majority of studies have focused on linear optical momentum transfer through radiation pressure, we have previously shown the transfer of spin angular momentum (SAM) to a trapped birefringent microparticle, “vaterite” in vacuum recording rotation rates of up to 10 MHz [8]
In order to model the correlated motion between two optically bound microparticles, we employ the theoretical approach of Meiners and Quake [23] and Bartlett et al [24], which includes the hydro-/aero-dynamic coupling between the particles, and we extend the theory to include the optical coupling between the particles in the underdamped case [25]
Summary
A central theme in levitated optomechanics is the trapping and control over all the degrees of freedom of mesoscopic particles levitated in vacuum. The key step is to conclusively demonstrate that the two particles interact and that their dynamical motion is inherently linked through a process known as optical binding [14,15,16,17] This is what we present here with clear evidence of the optical coupling (binding) of two such trapped particles in vacuum, each acting as a harmonic oscillator. The optically bound array of rotating microparticles exhibits cooperative motion whose CoM is stabilized by gyroscopic cooling Such an optically coupled and cooled array of micro-gyroscopes in levitated optomechanics may provide a future route for exploring multiparticle entanglement and quantum friction
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