8,102 research outputs found
Free-space propagation of high dimensional structured optical fields in an urban environment
Spatially structured optical fields have been used to enhance the functionality of a wide variety of systems that use
light for sensing or information transfer. As higher-dimensional modes become a solution of choice in optical
systems, it is important to develop channel models that suitably predict the effect of atmospheric turbulence on
these modes. We investigate the propagation of a set of orthogonal spatial modes across a free-space channel
between two buildings separated by 1.6 km. Given the circular geometry of a common optical lens, the orthogonal
mode set we choose to implement is that described by the Laguerre-Gaussian (LG) field equations. Our study focuses
on the preservation of phase purity, which is vital for spatial multiplexing and any system requiring full quantumstate
tomography. We present experimental data for the modal degradation in a real urban environment and draw a
comparison to recognized theoretical predictions of the link. Our findings indicate that adaptations to channel
models are required to simulate the effects of atmospheric turbulence placed on high-dimensional structured
modes that propagate over a long distance. Our study indicates that with mitigation of vortex splitting, potentially
through precorrection techniques, one could overcome the challenges in a real point-to-point free-space channel in
an urban environment
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