Generation of vortex and partially coherent laser beams based on fiber array coherent combining

V. V. Dudorov; V. P. Aksenov; V. V. Kolosov; M. E. Levitsky; T. D. Petukhov; A. P. Rostov

doi:10.1117/12.2502158

9 October 2018 Generation of vortex and partially coherent laser beams based on fiber array coherent combining

V. V. Dudorov, V. P. Aksenov, V. V. Kolosov, M. E. Levitsky, T. D. Petukhov, A. P. Rostov

Proceedings Volume 10787, Environmental Effects on Light Propagation and Adaptive Systems; 107870M (2018) https://doi.org/10.1117/12.2502158
Event: SPIE Remote Sensing, 2018, Berlin, Germany

Abstract

The generation of optical beams with a possibility of quick variations in the orbital angular momentum (OAM) and the degree of spatial coherence is shown in laboratory experiments. The methods for OAM and coherence control are based on the phase control in the fiber array optical channels. The approach suggested allows one to change the OAM (the topological charge of a vortex beam) with a high speed determined by the phase shifter operation speed. The generation of a vortex beam is shown for six coherent Gauss-like beams arranged in a circle and having a constant phase shift between neighboring beams, providing the total phase shift equal to 2π around the circle. It is shown that the far field is characterized by an annular intensity distribution and a spiral-like distribution of the Poynting vector. In addition, the features of the OAM and the topological charge of a fiber-array-based vortex beam in a homogeneous medium are investigated in numerical experiments. The method for controlling the length of spatial coherence of the beam synthesized is based on introducing pseudo-random phase fluctuations in a fiber array. The value of the coherence length which exceeds the subbeam size is set by the correlation function of pseudo-random phase fluctuations in neighboring subbeams. The value of the coherence length smaller than beamlet size is set by the divergence of the subbeams with delta correlated phase fluctuations. The effect of the number of pseudo-random realizations of the fiber array phase on the average intensity distribution is studied in the laboratory experiments. The influence of the spatial coherence of the laser beam on the bit error rate of FSO communication systems in a turbulent atmosphere is studied theoretically.

Conference Presentation

Citation Download Citation

V. V. Dudorov, V. P. Aksenov, V. V. Kolosov, M. E. Levitsky, T. D. Petukhov, and A. P. Rostov "Generation of vortex and partially coherent laser beams based on fiber array coherent combining", Proc. SPIE 10787, Environmental Effects on Light Propagation and Adaptive Systems, 107870M (9 October 2018); https://doi.org/10.1117/12.2502158

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