New method of creating twisted light may allow fibers to carry more information
September 24, 2013
The method has the potential to generate twisted light in shorter pulses, higher intensities, and a much wider range of wavelengths (including X-rays) than is currently possible.
First described two decades ago, twisted light is attracting attention from researchers in fields as diverse as telecommunications, quantum computing, condensed matter research and astronomy because of one unique property:
Researchers have demonstrated that it can transmit more information through fiber optic cables than the current industry standard.
Creating twisted light with an electron beam
Until now, researchers created twisted light by shooting laser beams through masks or holographic gratings. But a team of accelerator physicists from SLAC and UCLA has shown they can create it with a beam of electrons, in much the same way SLAC’s Linac Coherent Light Source (LCLS) X-ray laser uses electrons to generate pulses of X-ray laser light.
There are several advantages to generating corkscrew light beams this way, said SLAC postdoctoral researcher Erik Hemsing, who is lead author of a paper in the September issue of Nature Physics. Free-electron lasers can generate light in a vast range of wavelengths and in extremely short, bright pulses, opening up the possibility of generating orbital angular momentum (OAM) light at the X-ray wavelengths of, for example, LCLS.
In the case of corkscrewing light, researchers send two pulses — one containing electrons, the other laser light — through an undulator simultaneously.
The combination of laser pulse and undulator imprints an energy pattern on the electrons. As they pass through another grouping of magnets called a chicane, the electrons reposition themselves like race cars on a curve, and hit the next straightaway arranged in the shape of a corkscrew. This “helically microbunched” arrangement of electrons then enters a second undulator that causes them to wiggle and emit spiraling light.
Intense beams of spiraling X-ray light could also open the door to new condensed matter research, said Hemsing.