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28 February 2006 Optical micromanipulation of microscopic particles using axicon tipped fiber
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Trapping and manipulation of microscopic objects using fiber optical traps is gaining considerable interest, as these objects can be manipulated inside complex environments, thus removing the limitation of short working distance of the conventional optical tweezers. We show that an axicon like structure built on the tip of a single mode optical fiber produces a focused beam shape with a central hole, implying a very small fraction of the power traveling with rays nearly parallels to the optical axis. Interesting transportation behavior of polystyrene particles using the scattering forces from such an axicon tip fiber was observed. As the distance of the particle from the fiber tip increased, since almost no rays interact with the particle, the scattering forces decreased substantially. Therefore, velocity of the particle at different distances was found to depend much more critically on the particle size in contrast to the beam generated by the bare fiber. While the speed of transport could be increased linearly by increasing the laser power in both axicon tipped fiber and bare fiber, increased speed was observed for particles of larger sizes for both the fiber types. However, the fractional increase in speed for increased size of particles was found to be quite large for axicon tipped fiber as compared to the bare fiber. Use of the observed differences in speed of transportation of microscopic objects could be used to sort them based upon their size.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Carlo Liberale, Samarendra Kumar Mohanty, Khyati Samarendra Mohanty, Vittorio Degiorgio, Stefano Cabrini, Alessandro Carpentiero, Enrico Ferrari, Dan Cojoc, and Enzo Di Fabrizio "Optical micromanipulation of microscopic particles using axicon tipped fiber", Proc. SPIE 6095, Nanobiophotonics and Biomedical Applications III, 60950F (28 February 2006);


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