The efficient sorting of light's orbital angular momentum for optical communications

Abstract

We have developed a mode transformer comprising two custom refractive optical elements which convert orbital angular momentum states into transverse momentum states. This transformation efficiently measures the orbital angular momentum content of an input light beam, allowing the decoding of OAM states within a free-space communications channel. Turbulence is a key issue within such a channel. Through the use of a phase only spatial light modulator, turbulence is simulated, and the cross talk between detected OAM modes is observed. We study this crosstalk for eleven OAM modes, showing that turbulence equally degrades the purity of all the modes within this range. © 2012 SPIE.