Beams of light twisted into a corkscrew shape have carried data more than 3 kilometres over Vienna's skyline in an effort to increase the information-carrying capacity of electromagnetic waves.
Adding orbital angular momentum (OAM) to laser beams — when fluctuations of light waves are staggered along different parallel rays — can produce a theoretically infinite range of corkscrew patterns or modes. Mario Krenn and Anton Zeilinger at the University of Vienna and their colleagues used green laser light (pictured) with 16 different OAM modes to send data from a radar tower to a small detector across the city. They successfully transmitted small black-and-white pictures of Wolfgang Amadeus Mozart and other famous Austrians. The experiment showed that OAM modes can survive much longer trips through the atmosphere than expected.