Vortex beam generation by means of control of the piston shift of a fiber array using a phase forming DOE in active feedback loop

The results of an experiment on formation of a scalar vortex beam in the system of coherent combining of fiber laser beams are reported. Stabilization of phase relations between optical beams is achieved by placing a helicoid phase forming diffraction optical element (DOE) made as a phase plate with helical phase profile in the active feedback loop. Time-stable vortex beams with the topological charge p = ±1 are obtained. The vortex character of the obtained beams is confirmed by the results of interferometric measurements.