Tractor beam built from rings of laser light: David Ruffner and David Grier of New York University instead projected two Bessel beams side by side and used a lens to angle them so that they overlapped, creating a pattern of alternating bright and dark regions along the length of the beam. Fine-tuning the beam causes photons in the bright regions, initially flowing past a chosen particle in the beam, to scatter backwards. When these photons hit the particle, they knock it to the next bright region. The particle is thus constantly pushed close to the beam's source.
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