Optics and Photonics Society of Iran

Abstract-Measuring force in optical tweezers is provided by using a QPD positioned at the back-focal-plane of the microscope’s condenser based on interference model. Recently we showed, both theoretically and experimentally, that utilizing Talbot interferometer or moiré deflectometer in which the second grating is at one of the Talbot distances of the first one, we are able to detect Micro and/or Nano-particle displacements in optical traps with more sensitivity than the QPD detection method. In this paper, we extend the introduced detection method to 3 dimensions and drive the theoretical framework for detecting axial displacements of the trapped objects based on Rayleigh scattering description. Experimental results on 2.17 Micron bead approve the theoretical predictions and in addition we acquire a 150% improvement factor in detection sensitivity relative to the conventional QPD method.