Mode-dependent crosstalk and detection probability of orbital angular momentum of optical vortex beam through atmospheric turbulence

Abstract

The crosstalk of orbital angular momentum (OAM) modes is one of the most important issues for free-space optical communication. We theoretically derive a crosstalk model for Laguerre–Gaussian (LG) vortex beams propagating in turbulent atmosphere. The calculated crosstalk of different OAM modes in different turbulence by analytical expression is consistent with experimental measurements. Both theoretical and experimental results reveal that the crosstalk of high order LG vortex beams is more obvious in atmospheric turbulence. Different from the numerical calculation of the integral expression of the previous studies, this analytical expression can directly and quantitatively characterize the crosstalk and the law of different topological charges in vortex beams. Based on this analytical expression, the crosstalk widths of vortex beams with different topological charges can be calculated accurately, so that the optimal sets of OAM modes can be found more easily under each atmospheric turbulence condition.

The orbital angular momentum of a turbulent atmosphere and its impact on propagating structured light fields

“…In contrast, those studies that reported modal dependence did not resize higher order modes, resulting in larger second moment radii. Propagated vortex Gaussian modes [56] will have intensity profiles which depend on the initial charge in a similar way to the more obvious cases of LG [57] and IG [31] modes. According to our model, this is all resolved by understanding that turbulence is dependent on a beam's size and not its OAM.…”

“…In contrast, numerical studies of entangled OAM states in turbulence found that higher order single photon LG states were less robust than lower order ones [55]. Along with the demonstration of a dependence on the initial OAM, other studies have shown that there is also a basis dependence: for example, different results are obtained when using vortex Gaussian beams in comparison to LG, optical vortex [56,57] and Ince-Gaussian beams [31]. Indeed, while these advancements have elucidated the detrimental effects of turbulence on OAM-carrying light fields, the nuances involved in the modal dependence argument are not settled since there is disagreement with early findings.…”

Vector mode decay in atmospheric turbulence: a quantum inspired analysis

“…where P ( , m) = |c ,m | 2 is the conditional probability for the mode | to exchange energy with the mode |m . For Kolmogorov turbulence, the probabilities have been determined analytically [66] and are symmetric about | | for weak turbulence. With this in mind, we can now describe the state of our CVV mode after it traverses the turbulent channel.…”

Robust structured light in atmospheric turbulence

“…What is invariant is its vectorness, how inhomogeneous the polarization structure is (but not how it looks), which can potentially be exploited for error-free optical communication 22 . This modal scattering-induced cross talk decreases the information capacity of classical atmospheric transmission channels, 23 – 32 while reducing the degree of entanglement in quantum links 32 – 41 Mitigating this remains an open challenge that has been intensely studied.…”