Five-dimensional cooling and nonlinear dynamics of an optically levitated nanodumbbell

Abstract

Optically levitated nonspherical particles in vacuum are excellent candidates for torque sensing, rotational quantum mechanics, high-frequency gravitational wave detection, and multiple other applications. Many potential applications, such as detecting the Casimir torque near a birefringent surface, require simultaneous cooling of both the center-of-mass motion and the torsional vibration (or rotation) of a nonspherical nanoparticle. Here we report five-dimensional cooling of a levitated nanoparticle. We cool the three center-of-mass motion modes and two torsional vibration modes of a levitated nanodumbbell in a linearly polarized laser simultaneously. The only uncooled rigid-body degree of freedom is the rotation of the nanodumbbell around its long axis. This free rotation mode does not couple to the optical tweezers directly. Surprisingly, we observe that it strongly affects the torsional vibrations of the nanodumbbell. This work deepens our understanding of the nonlinear dynamics and rotation coupling of a levitated nanoparticle and paves the way towards full quantum control of its motion.

Initiating revolutions for optical manipulation: the origins and applications of rotational dynamics of trapped particles

“…Importantly, this is larger than the air damping torque at 10 À 9 mbar, a pressure within reach of those at which optical levitation of nanoparticles has already been achieved [43]. This certainly suggests that tests of quantum friction may be possible in the near future: levitated nanospheres have now been trapped at sub-wavelength distances from surfaces [267], and stabilisation of the relative position of particle and surface may be accomplished using either gyroscopic stabilisation [145] or feedback cooling of the translational motion [37,38,233]. Similarly, Xu and Li calculated that measurements of the torque exerted due to Casimir effects between a librating, levitated nanorod and a flat birefringent plate [231] are also within reach of state-of-the-art experiments.…”

“…have achieved μHz-level linewidths by driving the spinning motion with a periodically modulated polarisation [213]. Bang et al [233] recently reported cooling of all translational modes plus both librational modes of optically-levitated nanodumbbells, reaching temperatures below 5 K for the translation and around 10 K for the librational modes. The remaining degree of freedom, about the long axis of the dumbbell, was free to undergo rotation and perturbs the librational modes.…”

“…Proposals have also been made for reaching the ground state of librational motion via active feedback cooling for ellipsoidal particles [84], while Seberson et al showed that an asymmetric potential generated by elliptical polarisation or by using two perpendicular laser beams may also allow ground-state cooling of the libration [230]. This latter scheme has very recently been implemented by Bang et al [233], although the librational temperatures they achieved remain in the Kelvin regime. High-purity nanodiamond/ferromagnet hybrid particles have also been proposed as a promising candidate for librational ground-state cooling [245].…”

Dynamic Analysis and Simulation of an Optically Levitated Rotating Ellipsoid Rotor in Liquid Medium

“…Previous experiments have shown that a levitated rotating particle's rotational axis is not strictly fixed in the inertial space, partially due to its precession motion and nutation motion [22,23,27]. A levitated micro-sized sphere can measure the external torque by detecting the variation of the rotation rate and precession angle.…”

Optimal position detection of a dipolar scatterer in a focused field

“…One of the crucial ingredients for quantum control of these modes has been the optimization of their optical detection [21]. While first steps to measure and feedback-control the libration modes of levitated nanoparticles have been taken [8,22], an understanding of the optimal detection process for the orientation of an optically levitated dumbbell is still missing.…”