Experimental verification of the effects of atmospheric turbulence and retro-reflection on laser beams with orbital angular momentum

Retro-reflectors often find use in long-range laser propagation experiments. They double the propagation distance and cancel atmospheric tip/tilt alleviating the hardware requirements on the laser transceiver system. On the other hand, the effects that a retro-reflector can have on collimated or focused laser beams have not been thoroughly investigated. Additionally, for use in combination with beams carrying orbital angular momentum, which become increasingly popular in free-space optical communications, retro-reflector's effect must also be analysed. Demodulation efficiency of a communications system based on such beams is very sensitive to the fidelity of helical wavefronts and therefore retroreflector's effect on both amplitude and phase for collimated and focused orbital angular momentum beams should be studied.