All-fiber phase actuator based on an erbium-doped fiber amplifier for coherent beam combining at 1064 nm

Laser Zentrum Hannover e V, Hannover, Germany.
Optics Letters (Impact Factor: 3.29). 02/2011; 36(4):448-50. DOI: 10.1364/OL.36.000448
Source: PubMed


Active phase control in fiber amplifiers is of considerable interest for low-noise single-frequency amplifiers and for coherent beam combining. We demonstrate phase control at 1064 nm by use of an erbium-doped fiber. We investigated the phase shift by guiding the beam through an erbium-doped fiber amplifier in a Mach-Zehnder configuration and applied the results to stabilize the relative phase of two ytterbium-doped fiber amplifiers. To the best of our knowledge, this is the first demonstration of an all-fiber coherent beam combining at 1064 nm employing an erbium-doped fiber as a phase actuator.

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    • "As for the optical impact on the repetition rate change, there were two effects: (1) the interaction between the atoms of the gain media and electromagnetic radiation and (2) the nonlinear effect caused by the third-order susceptibility [29]. Both of these two optical effects should be proportional to the occupation of the upper laser level [16]. Therefore, the control bandwidth of the additional Er fiber would be mainly limited by the upper level lifetime. "
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    ABSTRACT: Coherent beam combining enables power scaling beyond the limits of single amplifiers. Therefore, improving the performance and simplicity of coherent combination techniques is of great interest for many high power applications. Here, we show all-fiber coherent beam combining of two ytterbium doped amplifiers with and without a dedicated phase actuator and a total output power up to 25 W. Instead of a dedicated phase actuator, we directly controlled the two ytterbium amplifiers to also stabilize their relative phase. We compared the performance of this method with phase stabilization using two piezo driven fiber stretchers. In both cases, power noise was dominated by the single amplifier.
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