Using polarimetry to measure the rotation of calcite in an optical trap

Abstract

The birefringent quality of calcite causes a change in the light’s angular momentum when directed through a crystal. This quality, when applied using optical tweezers, allows us to induce torque and rotate particles while held with the tweezers. To measure the torque induced, we use a method called polarimetry to determine the change in polarization of the light (and there-fore the change in angular momentum). We show our resulting polarization analyses and a comparison of our experimentally measured and calculated torque values. Keywords: Physics, Optics, Optical tweezers, Optical trapping, Po-larimetry, MATLAB, Calcite, Birefringence