Optically driven ultra-stable nanomechanical rotor

Abstract

Nanomechanical devices have attracted the interest of a growing interdisciplinary research community, since they can be used as highly sensitive transducers for various physical quantities. Exquisite control over these systems facilitates experiments on the foundations of physics. Here, we demonstrate that an optically trapped silicon nanorod, set into rotation at MHz frequencies, can be locked to an external clock, transducing the properties of the time standard to the rod’s motion with a remarkable frequency stability f r/Δf r of 7.7 × 1011. While the dynamics of this periodically driven rotor generally can be chaotic, we derive and verify that stable limit cycles exist over a surprisingly wide parameter range. This robustness should enable, in principle, measurements of external torques with sensitivities better than 0.25 zNm, even at room temperature. We show that in a dilute gas, real-time phase measurements on the locked nanorod transduce pressure values with a sensitivity of 0.3%.

Recent Progress in Optical‐Resonance‐Assisted Movement Control of Nanomotors

“…Because of the collision with the gas molecules in the vacuum chamber, the Si nanorod motor is pushed to regions of different light intensities in the laser trap from time to time, resulting in a very broad distribution of its rotational frequency. One can improve the rotation frequency stability by periodically switching the laser polarization between linear and circular . With this configuration, researchers have achieved the stable trapping and rotation of a Si nanorod over 4 continuous days with the locked frequency at 1.11 MHz and the full width at half maximum (FWHM) at 1.3 μHz according to the power spectral density measurement (Figure g) .…”

“…Copyright 2016, American Chemical Society. d−g) Si rotary nanomotors in vacuum driven by circularly polarized laser light . An individual Si nanorod motor is trapped in vacuum by the standing light wave formed by two counterpropagating 1550 nm laser beams (d).…”

“…Usually the distribution of the rotational frequency is broad because the collision between the nanomotor and the gas molecules pushes the nanomotor to regions of different light intensities. g) The rotation frequency stability can be improved by periodically switching the laser polarization between linear and circular . (d−f) Reproduced with permission .…”

“…Copyright 2017, Optical Society of America. (g) Reproduced with permission . Copyright 2017, Springer Nature.…”

Cavity optomechanics in a levitated helium drop

“…The rotational motion of a levitated liquid differs from that of a levitated solid (described in Refs. [68][69][70][71][72][73][74][75]) in several important respects. These include the liquid's electromagnetic and mechanical isotropy (which should more closely approximate free rotation),the independence between the liquid's external shape and its rotation, and, in the case of superfluid 4 He, dissipationless nonrigid body rotational motion.…”