Next generation Yb-doped fibers for high-power, narrow-linewidth lasers

Nicholson, Jeffrey W.; DeSantolo, A.; Windeler, R.S.; Monberg, E.; Lukonin, V. P.; Pincha, Jose; Hariharan, A.; Xu, Xiaoshu; Williams, Greg; Goldberg, Zelanna; Rosales-Garcia, Andrea; Kristensen, Poul; Knight, D. J. E.; DiGiovanni, D. J.

doi:10.1117/12.2614611

Cited by 8 publications

(6 citation statements)

References 21 publications

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“…With higher amplifier power level and broader linewidths to compensate for non-linear effects, the accuracy of the path length matching will have to subsequently increase. With narrow linewidth lasers having been demonstrated at 2.7 kW [7] and the promise of higher power levels [8] in the future, path length variability will increase, but should still be compensable.…”

Section: Discussionmentioning

confidence: 99%

Beam-combinable high-power fiber laser sources for directed energy applications

Holten,

Flores,

Ehrenreich

et al. 2024

High-Power Laser Ablation VIII

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We discuss methods and lessons learned during the integration and testing of five individual kW-class fiber amplifiers seeded with pseudorandom phase-modulated light, using a 1x5 Diffractive Optical Element (DOE). Each amplifier is capable of producing approximately 1.2 kW of near diffraction-limited output power (M2 <1.1). Low power samples from each amplifier are used for active polarization control. Phase control of each amplifier was accomplished using a low power combined beam sample and AFRL's Locking of Optical Coherent via Single-detector Electronic-frequency Tagging (LOCSET) control system. Approximately 5 kW of signal output was achieved with a combined efficiency of 82%. Losses in the system arise from DOE efficiency limitations, Amplified Spontaneous Emission (ASE), polarization errors, uncorrelated wavefront errors, optical path length mismatches, and beam misalignments. We discuss the impact of recent amplifier developments and how these developments impact this beam combining method.

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Section: Discussionmentioning

confidence: 99%

Beam-combinable high-power fiber laser sources for directed energy applications

Holten,

Flores,

Ehrenreich

et al. 2024

High-Power Laser Ablation VIII

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“…The decreased TOC 17.5-µm-MFD fiber shows lower SBS threshold compared with the standard 20-µm-MFD fiber (Figure 4). This shows that the MFD must still be increased to further increase the SBS threshold and reduce other nonlinearities, which is attainable by implementing advanced designs with high HOM bend loss 2,11 . This provides a path to higher performance gain fibers, combining the benefit of low-TOC glass gain medium with high HOM suppression fiber designs for low-nonlinearity and TMI-free fiber laser operation at the multi-kilowatt level.…”

Section: Methodsmentioning

confidence: 99%

5.2 kW single-mode output power from a Yb 20/400 fiber with reduced thermo-optic coefficient

Rosales-García,

Jensen,

Kristensen

et al. 2024

Fiber Lasers XXI: Technology and Systems

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We report the performance of an LMA Yb-doped fiber, designed for increasing the transverse mode instability threshold and minimizing nonlinear effects in multi-kilowatt class fiber lasers, by reducing the thermo-optic coefficient of the fiber core, compared with that of standard aluminophosphosilicate Yb-doped fibers. A TMI-free 5.2 kW single-mode output power from a Yb 20/400 fiber with a 17.5 µm mode-field diameter was achieved in a broad bandwidth, co-pumped amplifier with 78% optical-to-optical efficiency, while a 4 kW signal output was attained in a 26 GHz linewidth amplifier. Negligible photodarkening loss was observed during 150 hour laser operation at 2 kW.

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“…Previously, we reported on a next-generation strategy to increase the HOM losses in Yb-doped gain fibers that were compatible with high-power laser systems 5 . This approach allowed for simultaneously increasing the MFD of the fundamental mode while also maintaining high TMI thresholds, even for higher-absorption fibers with increased heat load.…”

Section: Introductionmentioning

confidence: 99%

5 kW single-mode output power from Yb-doped fibers with increased higher-order mode loss

Nicholson¹,

Pincha²,

Kansal³

et al. 2023

Fiber Lasers XX: Technology and Systems

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We report results from a new Yb-doped gain fiber with increased higher-order-mode (HOM) loss, compared to conventional step-index fibers. The fiber had 20 µm mode-field diameter (MFD), high absorption, and high transverse-mode instability (TMI) threshold. TMI-free operation with 5 kW output power was demonstrated from a 9 m length of gain fiber, limited by pump power. The large MFD and high absorption allowed for a 7.5 m long amplifier with greater than 80% o-o efficiency and the Raman peak more than 50 dB below the signal. These results were also enabled by a new, small-size, 7+1:1 pump-signal combiner.

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Next generation Yb-doped fibers for high-power, narrow-linewidth lasers

Cited by 8 publications

References 21 publications

Beam-combinable high-power fiber laser sources for directed energy applications

Beam-combinable high-power fiber laser sources for directed energy applications

5.2 kW single-mode output power from a Yb 20/400 fiber with reduced thermo-optic coefficient

5 kW single-mode output power from Yb-doped fibers with increased higher-order mode loss

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