Abstract
We describe an innovative data transmission scheme exploiting optical vortices to multiplex and demultiplex independent data channels in a standard asynchronous laser link. We report extensive results of the proof of concept of the method, successfully used to transmit two parallel ASCII strings, demultiplexed and decoded in the far field of the radiation beam. A phase locked two arms interferometer is proved to be effective even accessing a small portion of the beam only. Results prove the robustness and reliability of the method to perform dense-code free space transmissions over long distances even in presence of wavefront distortions. Applications and the extension to a larger number of parallel channels are discussed.
Highlights
Radiation with Orbital Angular Momentum (OAM) has been discovered [1,2,3,4] and formalized [5] at the end of the 20th century, proving that radiation with phase screw dislocations is solution of the Maxwell Equations
A number of experiments and applications have been conceived and performed in different fields of fundamental research and applied sciences: a few examples are in microscopy, to enhance the resolution limit [6,7]; in atomic physics, to increase the probability of non-dipolar transitions [8,9]; in astrophysics, to realize broadband coronagraphy [10,11,12], as well as to explore novel emission processes [13,14]
In [32,33] we have shown the effective feasibility of local measurements of the topological charge of OAM radiation
Summary
Radiation with Orbital Angular Momentum (OAM) has been discovered [1,2,3,4] and formalized [5] at the end of the 20th century, proving that radiation with phase screw dislocations is solution of the Maxwell Equations. A complementary area of interest deals with information, both in the classical [15,16,17,18,19,20,21,22,23,24,25] and quantum realms [26,27] In both cases the main benefit stems from the additional degree of freedom introduced by the orbital angular momentum Lz = hl/(2π), where l is an integer called topological charge and h is the Planck’s constant. To the two orthogonal polarization states, the number of possible orthogonal states of OAM radiation is not limited in principle, making it possible to realize dense–coding information in a purely classical way by exploiting the helicity of the wavefront, which exhibits an azimuthal phase dependence lθ of the radiation field, where θ is the geometrical azimuthal angle
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