Divergence-degenerate spatial multiplexing towards future ultrahigh capacity, low error-rate optical communications

Abstract

Spatial mode (de)multiplexing of orbital angular momentum (OAM) beams is a promising solution to address future bandwidth issues, but the rapidly increasing divergence with the mode order severely limits the practically addressable number of OAM modes. Here we present a set of multi-vortex geometric beams (MVGBs) as high-dimensional information carriers for free-space optical communication, by virtue of three independent degrees of freedom (DoFs) including central OAM, sub-beam OAM, and coherent-state phase. The novel modal basis set has high divergence degeneracy, and highly consistent propagation behaviors among all spatial modes, capable of increasing the addressable spatial channels by two orders of magnitude than OAM basis as predicted. We experimentally realize the tri-DoF MVGB mode (de)multiplexing and data transmission by the conjugated modulation method, demonstrating lower error rates caused by center offset and coherent background noise, compared with OAM basis. Our work provides a potentially useful basis for the next generation of large-scale dense data communication.

Towards higher-dimensional structured light

“…3a . Recently this DoF multiplexing has been extended to include path in novel ray-wave structured light to realise both ultrahigh capacity/speed and low bit-error-rate in communications 39 .

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Spatially Structured-Mode Multiplexing Holography for High-Capacity Security Encryption

“…Laguerre–Gaussian (LG) modes and Hermite–Gaussian (HG) modes are the eigensolutions of a paraxial wave equation, which are capable of composing complete and orthogonal bases. LG modes feature a circular symmetry and are directly related to the OAM of photons, which play an important role in rotational Doppler shift, optical image processing, , and optical communications . LG modes are characterized by an azimuthal index l and a radial index p .…”

Nondiffracting Supertoroidal Light Pulses: Optical "Kármán Vortex Streets"

“…The topological properties of light have been a subject of fascination and intense research interest over the last half century [1][2][3] with implications for light-matter interactions [4][5][6], nonlinear physics [7][8][9], spin-orbit coupling [10][11][12], microscopy and imaging [13][14][15], metrology [16], and information transfer [17][18][19]. Light pulses can be simultaneously structured in space and time domains [20][21][22][23][24].…”