![\"abduction\"](\"http:\/\/www.blastr.com\/sites\/blastr\/files\/styles\/blog_post_media\/public\/images\/AlienAbductionTractorBeam.jpeg\")
\nWe are not at the stage of lifting cows quite yet!<\/em><\/p>\n
I posted a little about tractor beams before here<\/a>, which employ a Bessel beam. Prof David Grier at New York University, published a paper last year announcing that they have experimentally demonstrated such a class of tractor beams [2].<\/p>\n What is new?<\/strong> We are not the first to demonstrate experimentally the motion of particles in a beam where the intensity is homogeneous, but our method is a little bit simpler and more straightforward than previous efforts.<\/p><\/blockquote>\n Pavel Zem\u00e1nek<\/em><\/p>\n Particle sorting<\/strong> The fact that the effect of the polarisation of lights is so prominent is surprising and for sure will lead to further research.<\/p>\n Link<\/strong> Reference<\/strong> [2] Optical conveyors: A class of active tractor beams, D. B. Ruffner and D. G. Grier, Phys. Rev. Lett.<\/em> 109<\/strong>, 163903 (2012) [5 pages] <\/p>\n","protected":false},"excerpt":{"rendered":" Physicists in the Czech Republic have produced a simple example of an optical tractor beam using two laser beams [1]. Interestingly, they have also discovered a new technique for sorting microscopic particles. We are not at the stage of lifting cows quite yet! I posted a little about tractor beams before here, which employ a … Continue reading Optical tractor beams can sort small particles<\/span>
\nThe work of the physicists at the Institute of Scientific Instruments of the Academy of Sciences of the Czech Republic shows that a simpler version of a tractor beam is possible. Their tractor beam comprises of two laser beams brought to a focus with a lens, which can easily be done using a standard commercial microscope system. They found that by focusing the light inwards they could generate the same effect as if they had employed a Bessel beam.<\/p>\n
\nAn unexpected effect is that the particles are pushed or pulled by the laser light depending on both the size of the particles and the polarization of the light. This allowed the researchers to separate mixtures of two different sized particles by changing the polarisation of the light.<\/p>\n![\"scotty\"](\"http:\/\/images3.wikia.nocookie.net\/__cb20120316184334\/memoryalpha\/en\/images\/thumb\/e\/ec\/Montgomery_Scott%2C_Generations.jpg\/180px-Montgomery_Scott%2C_Generations.jpg\")
\nScotty would be proud … (Image courtesy of http:\/\/en.memory-alpha.org)<\/p>\n
\nOptical tractor beam sorts tiny particles<\/a> (Physics World)(Jan 24, 2013)<\/p>\n
\n[1] O. Brzobohat\u00fd, V. Kar\u00e1sek,\tM. \u0160iler, L. Chv\u00e1tal, T. \u010ci\u017em\u00e1r\t & P. Zem\u00e1nek, Experimental demonstration of optical transport, sorting and self-arrangement using a \u2018tractor beam\u2019, Nature Photonics<\/em> (2013) doi:10.1038\/nphoton.2012.332 (Link<\/a>)<\/p>\n