A new method of harnessing the properties of light waves that can radically increase the amount of data they carry has been discovered by researchers at the University of California, Berkeley. They demonstrated the emission of discrete twisting laser beams from antennas made up of concentric rings roughly equal to the diameter of a human hair, small enough to be placed on computer chips.
The research, reported in a paper published in the journal Nature Physics, throws wide open the amount of information that can be multiplexed, or simultaneously transmitted, by a coherent light source. Previously, there had been fundamental limits to the number of coherent twisted lightwaves that could be directly multiplexed.
"It's the first time that lasers producing twisted light have been directly multiplexed," said study principal investigator Boubacar Kanté, the Chenming Hu Associate Professor at UC Berkeley's Department of Electrical Engineering and Computer Sciences. "We've been experiencing an explosion of data in our world, and the communication channels we have now will soon be insufficient for what we need. The technology we are reporting overcomes current data capacity limits through a characteristic of light called the orbital angular momentum. It is a game-changer with applications in biological imaging, quantum cryptography, high-capacity communications and sensors."
Kanté, who is also a faculty scientist in the Materials Sciences Division at Lawrence Berkeley National Laboratory (Berkeley Lab), has been continuing this work at UC Berkeley after having started the research at UC San Diego. The first author of the study is Babak Bahari, a former Ph.D. student in Kanté's lab.
Kanté said that current methods of transmitting signals through electromagnetic waves are reaching their limit. Frequency, for example, has become saturated, which is why there are only so many stations one can tune into on the radio. Polarization, where lightwaves are separated into two values – horizontal or vertical – can double the amount of information transmitted. Filmmakers take advantage of this when creating 3D movies, allowing viewers with specialized glasses to receive two sets of signals – one for each eye – to create a stereoscopic effect and the illusion of depth.