Application of optical phase lock loops in coherent beam combining

Abstract

Coherent Beam Combining (CBC) technology holds the promise of enabling laser systems with very high power and near-ideal beam quality. In this work we propose and demonstrate a novel CBC servo system using optical phase lock loops for phase control. This servo system is based on entirely electronic components and, consequently, can be considerably more compact and less expensive compared to servo systems made of optical phase/frequency shifters. In the proof-of-concept experiments we have combined two 100mW 1064nm commercial semiconductor lasers with the filled-aperture approach at an efficiency of 94% and also two 50mW 1538nm commercial semiconductor lasers using the tiled-aperture approach with a strehl ratio of 0.9. In addition, we also present a theoretical consideration of the influence of various sources of noise on the combining efficiency of a cascaded filled-aperture CBC system.

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