Fourty years of optical manipulation

The advancements in the optical technologies that enable researchers to make significant developments in the field of physics and biology have been discussed. One of the researchers, Arthur Ashkin, has demonstrated trapping using two counter-propagating beams and using a single beam that was obtained by propagating a beam vertically and using gravity to balance the radiation pressure force. The optical tweezers system has been introduced that uses a laser source passed through two telescope systems, the first to expand the beam to slightly overfill the back aperture of the microscope objective and the second to make the beam at the microscope conjugate with the beam on a steering mirror. The two multibeam techniques that are widely used includes scanning and holographic. The scanning techniques involve a beam that is scanned very rapidly across the particles of interest. The holographic techniques involve an input Gaussian beam, which has its phase modulated into that of target intensity at the focal plane of the microscope objective.