Back Focal Plane Interferometry for Holographic Optical Traps

Abstract

English: Since its invention in 1986, optical trapping as a tool to manipulate microparticles non-invasively has found many applications in physics and biology. Force measurement on biomaterials is a potential application of optical tweezers which requires precise position detection. Back focal plane interferometry has become a commonly precise method for position detection, but it is limited to single trap calibration. However, the study of complex biological systems requires simultaneous multiple trap manipulation. Time-sharing a trap at kHz by acousto-optic-deflectors produces multiple independent tweezers, but limited to two dimensions. In this work, we aim to combine the versatility of digital holography for simultaneous multiple manipulation with the precision of back focal plane interferometry for force measurement. A holographic optical system set-up has been built and used to generate two traps with orthogonal polarizations: a fixed trap useful for measuring forces, and a holographic tweezer which allows dynamic manipulation. This method represents a step towards simultaneous manipulation with many holographic traps and precise position detection with only one trap