Output laser coupler for coherent beam combining

Victor I. Kopp; Jongchul Park; Jonathan Singer; Daniel Neugroschl

doi:10.1117/12.2546474

21 February 2020 Output laser coupler for coherent beam combining

Victor I. Kopp, Jongchul Park, Jonathan Singer, Daniel Neugroschl

Proceedings Volume 11261, Components and Packaging for Laser Systems VI; 112610Y (2020) https://doi.org/10.1117/12.2546474
Event: SPIE LASE, 2020, San Francisco, California, United States

Abstract

We have developed a multichannel output coupler enabling coherent beam combining in the two-micron spectral range. We demonstrate experimentally the combining of multiple beams utilizing a set of thulium-doped, double-clad, singlemode optical fibers. The fibers are pumped by fiber-pigtailed laser diodes at 793 nm via (4+1)x1 pump-signal combiners. The combiners are fabricated using vanishing-core technology, which allows for preservation of the mode field through the tapering process. The output of individual lasing channels is generated over a 20 nm spectral band at around 1970 nm without any spectrally selective elements. The slope efficiency of individual lasers is approximately 50% with respect to the pump power. All lasing channels are fused into a monolithic silica structure with channel spacing of 32 microns on a triangular lattice. The fused assembly is fabricated in a glass microforming tapering process with a draw ratio of 3.9. In the process, the mode field at 1970 nm expands slightly to about 15 microns at the end of the taper, while the outer diameter is reduced from 2.3 mm to approximately 590 microns. The tapered end is straight polished and fusion spliced to a 600- micron diameter silica glass rod. The rod is cleaved and optically polished at zero degrees. The length of the rod is one half of the Talbot distance for optimal coherent beam combining. In the experiment, an antiphase supermode is observed when only the seven inner channels are pumped, and an in-phase supermode is excited when the number of channels is nineteen or larger.

Conference Presentation

Citation Download Citation

Victor I. Kopp, Jongchul Park, Jonathan Singer, and Daniel Neugroschl "Output laser coupler for coherent beam combining", Proc. SPIE 11261, Components and Packaging for Laser Systems VI, 112610Y (21 February 2020); https://doi.org/10.1117/12.2546474

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