Near-Field GHz Rotation and Sensing with an Optically Levitated Nanodumbbell
Peng Ju, Yuanbin Jin, Kunhong Shen, Yao Duan, Zhujing Xu, Xingyu Gao, Xingjie Ni, Tongcang Li
Abstract
A levitated nonspherical nanoparticle in a vacuum is ideal for studying quantum rotations and is an ultrasensitive torque detector for probing fundamental particle–surface interactions. Here, we optically levitate a silica nanodumbbell in a vacuum at 430 nm away from a sapphire surface and drive it to rotate at GHz frequencies. The relative linear speed between the tip of the nanodumbbell and the surface reaches 1.4 km s –1 at a submicrometer separation. The rotating nanodumbbell near the surface demonstrates a torque sensitivity of (5.0 ± 1.1) × 10 –26 N m Hz –1/2 at room temperature. Moreover, we probed the near-field laser intensity distribution beyond the optical diffraction limit with a nanodumbbell levitated near a nanograting. Our numerical simulations show that the system can measure the Casimir torque and will improve the detection limit of non-Newtonian gravity by several orders of magnitude.