Robust structured light in atmospheric turbulence

Abstract

Structured light is routinely used in free space optical communication channels, both classical and quantum, where information is encoded in the spatial structure of the mode for increased bandwidth. Unlike polarisation, the spatial structure of light is perturbed through such channels by atmospheric turbulence, and consequently, much attention has focused on whether one mode type is more robust than another, but with seemingly inconclusive and contradictory results. Both real-world and experimentally simulated turbulence conditions have revealed that free-space structured light modes are perturbed in some manner by turbulence, resulting in both amplitude and phase distortions. Here, we present complex forms of structured light which are invariant under propagation through the atmosphere: the true eigenmodes of atmospheric turbulence. We provide a theoretical procedure for obtaining these eigenmodes and confirm their invariance both numerically and experimentally. Although we have demonstrated the approach on atmospheric turbulence, its generality allows it to be extended to other channels too, such as underwater and in optical fibre.

Generation and detection of OAM-carrying beamlets for underwater optical systems using a HOBBIT system

“…Structured light is a very general term but will be restricted in this context to referring to any light fields with strong spatial inhomogeneity of amplitude, phase, polarization, and other parameters [10]. Following this definition, it has been shown that structured light provides unique capabilities with regards to probing through turbulent media [11]. Another study shows that other forms of structured light with polarization invariant properties are more resilient in non-ideal propagation conditions [12].…”