Optical vortex beams resemble cyclones with either left-hand or right-hand twist, depending on the orbital angular momentum (OAM) of the photons. Different degrees 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 communication links. Light beams at the same frequency but with different OAM levels can be used to transmit different information streams, and individual photons with different degrees of twist can be used to represent quantum data bits. When an optical vortex beam interacts with matter, it produces a rotational force (torque) on the matter that can be used as an optical spanner or optical tweezers to trap and manipulate microscopic particles or droplets.
For the first time, researchers from the Universities of Bristol and Glasgow in the UK and from the Universities of Sun Yt-Sen and Fudan in China have succeeded in integrating optical vortex beam emitters onto a silicon chip. With dimensions in the micrometer range – thousands of times smaller than conventional devices – the new emitters are based on silicon optical waveguides and can be made using standard integrated circuit fabrication technologies. The emitters can easily be interconnected to form large, complex arrays in photonic integrated circuits, and their potential application areas include communication, sensing, and microscopic particle manipulation. The optical vortex devices are so small that silicon chips holding thousands of emitters could be fabricated in high volume at very low cost, which could open up entirely new applications for optical vortex beams previously unattainable using bulk optics.