Three-axis rapid steering of optically propelled micro/nanoparticles

This paper presents the design and implementation of a three-axis steering system, wherein a micro/nanoparticle is optically trapped and propelled to serve as a measurement probe. The actuators in the system consist of a deformable mirror enabling axial steering and a two-axis acousto-optic deflector for lateral steering. The actuation range is designed and calibrated to be over $20μm$ along the two lateral axes and over $10μm$ along the axial direction. The actuation bandwidth of the two lateral axes is over 50 kHz and the associated resolution is 0.016 nm $(1σ)$⁠. The axial resolution is 0.16 nm, while the bandwidth is enhanced to over 3 kHz by model cancellation method. The performance of the three-axis steering system is illustrated by three sets of experiments. First, active Brownian motion control of the trapped probe is utilized to enhance trapping stability. Second, a large range three-dimensional (3D) steering of a $1.87μm$ probe, contouring a complex 3D trajectory in a $6×6×4μm3$ volume, is demonstrated. Third, a closed-loop steering is implemented to achieve improved precision.