Particle-like topologies of light in turbulent complex media

Abstract

The basic building blocks of many forms of optical topologies are particle-like singularities in phase and polarisation, giving rise to lines of darkness that weave complex threads in 3D space. Although known for half a century since seminal work on dislocations in wave trains, their behaviour in complex media remains under debate, especially with respect to their relative stability. Here we show that polarisation and phase vortices behave identically in one-sided turbulent complex channels. We perform complementary numerical and experimental studies using atmospheric turbulence as a test case, demonstrating agreement and equivalent dynamics. Our work addresses open questions on optical topologies and will be relevant to their harnessing for applications such as sensing, communication, imaging, and information transfer in noisy or complex environments.

Figures (3)

• Figure 1: (a) Singularity constellation distributions and (b) typical complex fields obtained for turbulent strengths $D/r_0=0,1,5$, respectively distributed across the rows. Within each panel, the top (bottom) row refers to the $\ell=1$ vortex encoded in the phase (polarisation) distribution. Each inset refers to the simulation distributions, while the rest corresponds to their respective experimental result. The marker colours in panel (a) represent their respective distance from the constellation centroid. In panel (b), brightness represents the total amplitude $|\psi|$, while the colours refer to the phase $\angle \psi$ for the scalar vortex and to the Stokes field phase $\text{atan}(S_2/S_3)$ for the polarisation vortex.
• Figure 2: Positional deviation radius $\sigma$ as a function of the turbulence strength $D/r_0$ for (a) the phase singularity case and (b) the polarisation singularity case. The same experiment was repeated with corrected beam waists (see main text), (c) for the phase singularity case and (d) for the polarisation singularity case. All plots show the outcomes for topological charges $\ell=1,2,3$, where the solid lines and hollow markers refer to the simulation results, while dashed lines and filled markers represent experiments.
• Figure 3: Experimentally retrieved positional deviation radius for the polarisation ($\sigma_{pol}$) and phase ($\sigma_{ph}$) vortices generated using the LG mode with uncorrected (circles) and corrected (triangles) beam waist with topological charges $\ell=1,2,3$. The black solid line refers to the experimental linear fit, with slope $0.8291 \pm 0.0458$. The dashed line corresponds to the theoretical linear fit, with slope $0.9971 \pm 0.0190$.