Scintillation of laser beams carrying orbital angular momentum propagating in a near-maritime environment

Abstract

Laser beams carrying orbital angular momentum (OAM) were propagated in a near-maritime environment along an 890 meter link across the Severn River at the United States Naval Academy. The OAM beams were generated using green light ( λ=532nm) and etched spiral phase plates with different topological charges. The light intensity fluctuations of Gaussian and beams carrying OAM with topological charges of 1, 6, and 8 were measured and the scintillation indices of each beam were compared. Additionally, atmospheric turbulence was measured using a co-aligned scintillometer along the 890 meter propagation path. During testing, a wide range of atmospheric conditions occurred and the refractive index structure parameter measurements ranged from 5×10−14 down to 5×10−15 m −2∕3. Our measurements of transmitted voltage in the radial intensity across the maritime link, and calculated scintillation index, for the Gaussian beam and laser beams carrying OAM indicate a weak reduction in scintillation index for increasing topological charge. To reduce the measurement uncertainty and improve upon statistical significance of our findings, additional testing is needed.