Abstract
A fraction of a laser beam array, whose unknown phase relationships must be set to prescribed values, is launched into a scattering media with random transmission. The resulting output speckle pattern is sampled by an array of photodiodes measuring the local light intensity. The data feed an innovative optimization process which controls a phase modulator array. Few iterations of the opto-numeric loop lead to efficient and fast phase locking on any desired wavefront.
Highlights
Array of tiled coherent laser beams, either from a laser array or derived from a single laser oscillator and further individually amplified, is a common approach to increase the power delivered by laser sources [1], [2]
We presented in this letter a new optimization technique based on an optical scattering process for setting the piston phase of a coherent laser beam array on any desired distribution
It is based on an optical scattering process which transforms the input beam array into a speckle pattern whose intensity is measured in a few transverse positions only
Summary
Array of tiled coherent laser beams, either from a laser array or derived from a single laser oscillator and further individually amplified, is a common approach to increase the power delivered by laser sources [1], [2]. For some other applications a fast non-mechanical beam steering is sought [6], [7], or a beam forming capability or a compensation of the distortions due to atmospheric turbulence [8] In those cases, the phase distribution in the array has to be no longer uniform. The proposed approach [13] shares some features with the Phase-Intensity Mapping (PIM) method [14], [15], since both are based on a phase intensity mapping device whose data obtained from multiple photodetectors served for an iterative optimization algorithm In contrast to the latter, the new technique permits phase-locking of the beams on any arbitrary phase distribution across the array, in particular for atmospheric distorsion compensation. It offers a great flexibility for a compact implementation, even for arrays of large size
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