Spectral beam combining of kW-class thulium-doped fiber lasers

Friedrich Möller; Tilman Lühder; Benjamin Yildiz; Till Walbaum; Thomas Schreiber

doi:10.1117/12.3001640

12 March 2024 Spectral beam combining of kW-class thulium-doped fiber lasers

Friedrich Möller, Tilman Lühder, Benjamin Yildiz, Till Walbaum, Thomas Schreiber

Proceedings Volume 12865, Fiber Lasers XXI: Technology and Systems; 128650S (2024) https://doi.org/10.1117/12.3001640
Event: SPIE LASE, 2024, San Francisco, California, United States

Abstract

Thulium-doped fiber amplifiers have been limited to average output powers of around 1 kW for over a decade. To achieve multi-kW powers around 2 μm wavelength, we propose using dual-grating Spectral Beam Combining (SBC). Three customized kW-class Tm-doped fiber amplifiers operating in the 2030-2050 nm range were developed. The amplifiers consist of three stages and are pumped with non-stabilized, fiber-coupled diode lasers at 790 - 795 nm. Singlemode, TMI-free output powers exceeding 800 W, with narrow linewidths of FWHM ⪅115 pm, were achieved and subsequently combined using highly efficient in-house fabricated reflection gratings. With an overall combining efficiency of 90 % and a thermal slope of the combining grating measured as 6.8 K/kW, scalability to kW-level powers is enabled. The combined output power achieved a record-breaking 1.91 kW with good beam quality (M² ⪅2) and potential for further optimization. Finally, the potential power scalability of this non-coherent combining approach to power levels exceeding 20 kW is discussed.

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Friedrich Möller, Tilman Lühder, Benjamin Yildiz, Till Walbaum, and Thomas Schreiber "Spectral beam combining of kW-class thulium-doped fiber lasers", Proc. SPIE 12865, Fiber Lasers XXI: Technology and Systems, 128650S (12 March 2024); https://doi.org/10.1117/12.3001640

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KEYWORDS

Reflection gratings

Diffraction gratings

Fiber amplifiers

Diffraction

Optical gratings

Semiconductor lasers

Transverse mode instability

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