Abstract

We demonstrate coherent combining (phase locking) of seven laser beams emerging from an adaptive fiber- collimator array over a $7\mathrm{km}$ atmospheric propagation path using a target-in-the-loop (TIL) setting. Adaptive control of the piston and the tip and tilt wavefront phase at each fiber-collimator subaperture resulted in automatic focusing of the combined beam onto an unresolved retroreflector target (corner cube) with precompensation of quasi-static and atmospheric turbulence-induced phase aberrations. Both phase locking (piston) and tip–tilt control were performed by maximizing the target-return optical power using iterative stochastic parallel gradient descent (SPGD) techniques. The performance of TIL coherent beam combining and atmospheric mitigation was significantly increased by using an SPGD control variation that accounts for the round-trip propagation delay (delayed SPGD).

© 2011 Optical Society of America

Deep turbulence effects mitigation with coherent combining of 21 laser beams over 7  km

Thomas Weyrauch, Mikhail Vorontsov, Joseph Mangano, Vladimir Ovchinnikov, David Bricker, Ernst Polnau, and Andrey Rostov
Opt. Lett. 41(4) 840-843 (2016)

Experimental demonstration of using divergence cost-function in SPGD algorithm for coherent beam combining with tip/tilt control

Chao Geng, Wen Luo, Yi Tan, Hongmei Liu, Jinbo Mu, and Xinyang Li
Opt. Express 21(21) 25045-25055 (2013)

Speckle-metric-optimization-based adaptive optics for laser beam projection and coherent beam combining

Mikhail Vorontsov, Thomas Weyrauch, Svetlana Lachinova, Micah Gatz, and Gary Carhart
Opt. Lett. 37(14) 2802-2804 (2012)

Comparative efficiency analysis of fiber-array and conventional beam director systems in volume turbulence

Mikhail Vorontsov, Grigory Filimonov, Vladimir Ovchinnikov, Ernst Polnau, Svetlana Lachinova, Thomas Weyrauch, and Joseph Mangano
Appl. Opt. 55(15) 4170-4185 (2016)

Coherent beam combination of seven 1.5 µm fiber amplifiers through up to 1 km atmospheric turbulence: near- and far-field experimental analysis

Bastien Rouzé, Laurent Lombard, Hermance Jacqmin, Anasthase Liméry, Anne Durécu, and Pierre Bourdon
Appl. Opt. 60(27) 8524-8533 (2021)