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 20 mu m along the two lateral axes and over 10 mu m along the axial direction. The actuation bandwidth of the two lateral axes is over 50 kHz and the associated resolution is 0.016 nm (1 sigma). 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 1.87 mu m probe, contouring a complex 3D trajectory in a 6x6x4 mu m(3) volume, is demonstrated. Third, a closed-loop steering is implemented to achieve improved precision.