Optical Vortices May Aid Free-Space Communication
HAIFA, Israel -- Researchers at the Technion-Israel Institute of Technology discovered that VCSELs can produce complex patterns of tiny optical vortices, each measuring no more than 2 µm across. Vortices are found throughout nature; optical vortices are like the miniature whirlpools left behind by the paddle of a canoe, and the direction of their wave motion rotates around a central axis like water around a drain.
However, Meir Orenstein and Jacob Scheuer found that the optical version of vortices has at least a few unusual features. Writing in the July 9 issue of Science, they noted that the number of vortices increases dramatically as the current fed into them is increased. When they doubled
the size of the VCSELs and tripled the laser threshold current, the resulting laser beams broke up to spontaneously form complex patterns of light and dark, including figure eights and bull's-eyes. These patterns include multiple vortices, which maintained their exact structure and direction of spin after propagating long distances in the air.
Because of the robustness of the vortex beams, Orenstein expects that they may be useful for the free-space communication that occurs between electronic chips and boards. The vortices avoid some of the problems associated with other means of optical interconnections, such as excess heat and air turbulence that can scatter and distort a beam. The quantity related to the magnitude of spinning would not be disrupted.
Optical vortices also have the potential to carry more information: Their presence or absence can indicate a "1" or a "0," while their charge magnitude and sign can be used to carry additional data. Orenstein commented, "If one can control those parameters in an optical source -- especially a miniature optical source -- one can attach an array of sources to an electronic processor which can transmit its information in high speed to another processor via this specialized optical signaling."
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