<title>Measurements of optical tweezers stiffness</title>

Abstract

We report an experimental study of the trapping efficiency of an optical tweezers system acting on spherical polystyrene particles in water solution. As force calibration method we used the viscous drag exerted by fluid flow. A parametric study of the efficiency of the trap was made as a function of bead diameter and objective NA. Optical tweezers were also characterized in terms of the optical potential well by measuring the displacement of trapped particles undergone to a viscous drag for fluid flow below the critical velocity. Trap stiffness was determined for particle size of 14.9 micrometers at different laser power.