Giant rotational speed induced by symmetry-selective focusing

Achieving ultra-high-speed rotation of a nanomotor has significant implications for multiple disciplines and fields, such as small force sensing, quantum optics, and material testing. We developed an angular meta-accelerator to amplify the rotational dynamics of a nanomotor in vacuum, achieving the same GHz-level of rotational frequencies as in the literature, but under intensities that are two orders of magnitude lower. A straightforward and intuitive approach to achieving the rotation of a nanomotor involves transferring angular momentum to the nanomotor. However, the availability of incident angular momentum inevitably imposes an upper limit on the nanomotor's performance. Here, the angular meta-accelerator we propose, a structure with high rotational symmetry (composed of spheres or other shapes), effectively enhances the rotational speed of the nanomotor by up to 200 times compared to the situation without the meta-accelerator. The significant improvement in nanomotor performance originates from the meta-accelerator's selective focusing capability, which reconfigures external influences on the nanomotor. We analyze the enhancement of nanomotor performance in depth by decomposing the total field into different scattering channels as well as considering the spatial distribution of the scattering field. This approach of utilizing supplementary devices to enhance the performance of target devices not only provides valuable insights into overcoming inherent limitations but also unveils substantial potential for the design and development of advanced, complex mechanical systems in the future.