22 February 2017 Coherent beam combining architectures for high power tapered laser arrays
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Proceedings Volume 10086, High-Power Diode Laser Technology XV; 100860O (2017) https://doi.org/10.1117/12.2252125
Event: SPIE LASE, 2017, San Francisco, California, United States
Abstract
Coherent beam combining (CBC) aims at increasing the spatial brightness of lasers. It consists in maintaining a constant phase relationship between different emitters, in order to combine them constructively in one single beam. We have investigated the CBC of an array of five individually-addressable high-power tapered laser diodes at λ = 976 nm, in two architectures: the first one utilizes the self-organization of the lasers in an interferometric extended-cavity, which ensures their mutual coherence; the second one relies on the injection of the emitters by a single-frequency laser diode. In both cases, the coherent combining of the phase-locked beams is ensured on the front side of the array by a transmission diffractive grating with 98% efficiency.

The passive phase-locking of the laser bar is obtained up to 5 A (per emitter). An optimization algorithm is implemented to find the proper currents in the five ridge sections that ensured the maximum combined power on the front side. Under these conditions we achieve a maximum combined power of 7.5 W.

In the active MOPA configuration, we can increase the currents in the tapered sections up to 6 A and get a combined power of 11.5 W, corresponding to a combining efficiency of 76%. It is limited by the beam quality of the tapered emitters and by fast phase fluctuations between emitters. Still, these results confirm the potential of CBC approaches with tapered lasers to provide a high-power and high-brightness beam, and compare with the current state-of-the-art with laser diodes.
Conference Presentation
© (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
G. Schimmel, S. Janicot, M. Hanna, J. Decker, P. Crump, G. Erbert, U. Witte, M. Traub, P. Georges, G. Lucas-Leclin, "Coherent beam combining architectures for high power tapered laser arrays", Proc. SPIE 10086, High-Power Diode Laser Technology XV, 100860O (22 February 2017); doi: 10.1117/12.2252125; https://doi.org/10.1117/12.2252125
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