Fabrication of large vaterite microspheres for optical trapping and rotation in high vacuum

Abstract

A single beam optical trapping system is used to trap and rotate silica and vaterite microspheres in high vacuum. Large vaterite microspheres with diameters up to 15 μm are fabricated with multi-stage precipitation reactions and are rotated in the trap through the transfer of spin angular momentum from the photons in the trapping beam to the spheres. An electro-optic modulator is used to vary the polarization of the trapping beam, allowing for control over the rotation with damping times on the order of a day and with rotation frequencies up to 10 MHz for 10 μm diameter spheres. While highly birefringent spheres are successfully trapped at moderate vacuum pressures (⪆10−2 mbar), poor reproducibility is observed for trapping spheres in high vacuum. This trapping behavior is found to be independent of the morphology, birefringence, and monodispercity of the spheres.