A space-time transcoder

ABSTRACT

Light with phase front carrying an orbital angular momentum (OAM) is useful in many fields, such as optical tweezers, astronomy. In optical communication, light encoded information in its OAM degrees of freedom enables networks to carry significantly more information and increase their capacity significantly. However, light with OAM has a difficulty in propagating in commercial optical fibers, while light in Gaussian mode encoded with time-bin is most suitable for transmission in fiber. Therefore it is crucially important to build up a bridge for interfacing lights with OAM and time-bin. Here, we report the realization of a photonic space-time transcoder, by which light with an arbitrary OAM superposition is experimentally converted into a time-bin Gaussian pulse and vice versa in principle. Furthermore, we clearly demonstrate that the coherence is conserved very well and there is no crosstalk between orthogonal modes. Such a photonic device is simple and theoretically can be built up in a scalable architecture. Our experimental demonstration paves a primary step towards mixed optical communication in free-space and optical fibre.