Integrated optical vortex emitters open up new applications

October 19, 2012 // By Nick Flaherty
Researchers in Bristol and Glasgow in the UK have integrated 'optical vortex beam' emitters onto a silicon chip for the first time, opening up new applications in telecommunications and sensors.

The new emitters developed at Bristol are only a few micrometres in size and thousands of times smaller than conventional elements. They are based on silicon optical waveguides and can be made using standard integrated circuit fabrication technologies and developed by a team that includes universities in Sun Yat-sen and Fudan in China.
"Our microscopic optical vortex devices are so small and compact that silicon micro-chip containing thousands of emitters could be fabricated at very low costs and in high volume," said Siyuan Yu, Professor of Photonics Information Systems in the Photonics Research Group at the University of Bristol, who led the research. "Such integrated devices and systems could open up entirely new applications of optical vortex beams previously unattainable using bulk optics."
Optical beams can look like a vortex or cyclone with the light rays 'twisted' either left-handed or right-handed, associated with the orbital angular momentum (OAM) of the photons. Different degree of twist can be used to transmit information – allowing more information to be carried by a single optical signal and increasing the capacity of optical communications links. Light beams at the same frequency but with different OAM values can be used to transmit different streams information and single photons can use these different degrees of twist to represent quantum information.
When such light interacts with matter, it also asserts a rotational force (a torque) on the matter that can be used as 'optical spanners' or 'optical tweezers' to trap and manipulate microscopic particles or droplets. Applications are also being developed in using such light for imaging and sensing purposes.
The emitters are easily interconnected with each other to form complex and large arrays in photonic integrated circuits, and could be used for applications including communications, sensing and microscopic particle manipulation.
"Perhaps one of the most exciting applications is the control of twisted light at the single photon level, enabling us to exploit the quantum mechanical properties