Propagation property of Laguerre-Gaussian beams carrying fractional orbital angular momentum in an underwater channel

Abstract

In the paper, we experimentally demonstrate the propagation property of Laguerre-Gaussian (LG) beams carrying fractional orbital angular momentum (FOAM) in an underwater environment. The effects of topological charge (TC), temperature gradient, and salinity on the transmission of the LG-FOAM beam in underwater turbulence are analyzed, and the optimum interval of TC for FOAM communication and their help for the improvement of system capacity are discussed. The results show that both the salinity and the temperature gradient have serious impacts on the beam, and meanwhile, the temperature gradient plays a heavier influence. Although the detection probability of one FOAM mode at the receiver side is lower than that nearest integer OAM mode, in the case of that topological charges used are limited, the interval-based mode-multiplexed communication using FOAM can increase the channel capacity.