  We have experimentally studied the degradation of mode purity for light beams
carrying orbital angular momentum (OAM) propagating through simulated
atmospheric turbulence. The turbulence is modeled as a randomly varying phase
aberration, which obeys statistics postulated by Kolmogorov turbulence theory.
We introduce this simulated turbulence through the use of a phase-only spatial
light modulator. Once the turbulence is introduced, the degradation in mode
quality results in cross-talk between OAM modes. We study this cross-talk in
OAM for eleven modes, showing that turbulence uniformly degrades the purity of
all the modes within this range, irrespective of mode number.
