Optical Rotation of Levitated Spheres in High Vacuum

A circularly polarized laser beam is used to levitate and control the rotation of microspheres in high vacuum. At low pressure, rotation frequencies as high as 6 MHz are observed for birefringent vaterite spheres, limited by centrifugal stresses. Due to the extremely low damping in high vacuum, the controlled optical rotation of amorphous SiO2 spheres is also observed at rates above severalMHz. At 10(-7) mbar, a damping time of 6 x 10(4) s is measured for a 10-mu m-diam SiO2 sphere. No additional damping mechanisms are observed above gas damping, indicating that even longer damping times may be possiblewith operation at lower pressure. The controlled optical rotation of microspheres at MHz frequencies with low damping, including for materials that are not intrinsically birefringent, provides a tool for performing precision measurements using optically levitated systems.