Comprehensive Theoretical Study of Mode Instability in High-Power Fiber Lasers by Employing a Universal Model and Its Implications

Tao, Rumao; Wang, Xiaolin; Zhang, Pu

doi:10.1109/jstqe.2018.2811909

Cited by 105 publications

(48 citation statements)

References 144 publications

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“…The experimental results obtained in this work can be now compared with former theoretical predictions. Smith et al [11], Naderi et al [12], Hansen et al [13] and Tao et al [14] all studied the influence of small seed modulations on the TMI threshold. All of them found that the seed modulations should lead to a decrease of the TMI threshold, which has been confirmed by our experimental observations.…”

Section: Seed Intensity-noisementioning

confidence: 99%

“…Additionally, the influence of small pump modulations on the TMI threshold was also studied and compared to the one of the seed modulations in [11,14]. Tao et al [14] described a similar impact of both noise sources on the TMI threshold, whereas Smith et al [11] even predicted a stronger influence of the seed modulations. Both results are in contradiction to our experimental findings, which clearly show that the pump intensity-noise has the strongest impact on the TMI threshold.…”

Section: Seed Intensity-noisementioning

confidence: 99%

“…In the past, the impact of pump and seed intensity-noise on TMI has only been studied theoretically [11][12][13][14]. Due to the different results obtained in the different studies and due to the lack of physical explanations, it is not clear so far which noise source affects the TMI threshold of fiber amplifiers the most: the pump or the seed intensitynoise.…”

Section: Introductionmentioning

confidence: 99%

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Intensity noise as a driver for transverse mode instability in fiber amplifiers

et al. 2020

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The effect of transverse mode instability (TMI) is currently the main limitation for the further average-power scaling of fiber laser systems with diffraction-limited beam quality. In this work a main driving force for TMI in fiber amplifiers is identified. Our experiments and simulations illustrate that the performance of fiber laser systems in terms of their diffraction-limited output power can be significantly reduced when the pump or seed radiation exhibit intensity noise. This finding emphasizes the fact that the TMI threshold is not only determined by the active fiber but, rather, by the whole system. In the experiment an artificially applied pump intensity-noise of 2.9% led to a reduction of the TMI threshold of 63%, whereas a similar seed intensitynoise decreased it by just 13%. Thus, even though both noise sources have an impact on the TMI threshold, the pump intensity-noise can be considered as the main driver for TMI in saturated fiber amplifiers. Additionally, the work unveils that the physical origin of this behavior is linked to the noise transfer function in saturated fiber amplifiers. With the gained knowledge and the experimental and theoretical results, it can be concluded that a suppression of pump-noise frequencies below 20 kHz could strongly increase the TMI threshold in high-power fiber laser systems.

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Section: Seed Intensity-noisementioning

confidence: 99%

Section: Seed Intensity-noisementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Intensity noise as a driver for transverse mode instability in fiber amplifiers

et al. 2020

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“…As for TMI effect, several potential 2 P. Ma et al suppressing methods had also been proposed and validated by investigating on its physical mechanism [30][31][32][33][34][35][36][37] . Generally, TMI effect could be suppressed by optimizing the doping area or imposing external bend loss of higher-order modes for mode selection [23][24][25][26][30][31][32][33] , reducing the core size or numerical aperture (NA) of the active fiber [27,28,31,34] , increase of the seed power [33] , weakening head load by optimizing the injected ratios of co-pumped and counterpumped laser [33,35,36] , decrease of quantum defect and/or pump absorption [33,35,37] . Nowadays, as high as 3 kW and 3.5 kW output powers with narrow bandwidths and near-diffraction-limited beam qualities had been respectively presented by using gold-coated specialty gain fiber [24] and low-NA active fiber [28] , while the configurations are not allfiberized and some bulk space components were employed.…”

Section: Introductionmentioning

confidence: 99%

“…Despite most of the high power, narrow-bandwidth fiber amplifiers being pumped by 976 nm laser diodes (LDs) for being favorable of SBS management, tandem pumping is a robust route for simultaneously decreasing the quantum defect and pump absorption for TMI suppression [33,37] . This technique had been widely used in high power fiber amplifiers with broadband spectral characteristics [38][39][40][41][42] , and the output powers had been remarkably scaled to be beyond 3.5 kW power level by several groups [38,41,42] .…”

Section: Introductionmentioning

confidence: 99%

High power all-fiberized and narrow-bandwidth MOPA system by tandem pumping strategy for thermally induced mode instability suppression

Meng

et al. 2018

High Pow Laser Sci Eng

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An all-fiberized and narrow-bandwidth master oscillator power amplification (MOPA) system with record output power of 4 kW level and slope efficiency of 78% is demonstrated. Tandem pumping strategy is tentatively introduced into the narrow-bandwidth MOPA system for thermally induced mode instability (TMI) suppression. The stimulated Brillouin scattering (SBS) effect is balanced by simply using one-stage phase modulation technique. With different phase modulation signals, SBS limited output powers of 336 W, 1.2 kW and 3.94 kW are respectively achieved with spectral bandwidths accounting for 90% power of ${\sim}$0.025, 0.17 and ${\sim}$0.89 nm. Compared with our previous 976 nm pumping system, TMI threshold is overall boosted to be ${>}$5 times in which tandem pumping increases the TMI threshold of ${>}$3 times. The beam quality ($M^{2}$ factor) of the output laser is well within 1.5 below the TMI threshold while it is ultimately saturated to be 1.86 with the influence of TMI at maximal output power. Except for SBS and TMI, stimulated Raman scattering (SRS) effect will be another challenge for further power scaling. In such a high power MOPA system, multi-detrimental effects (SBS, SRS and TMI) will coexist and may be mutual-coupled, which could provide a well platform for further comprehensively investigating and optimizing the high power, narrow-bandwidth fiber amplifiers.

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High-power, high-brightness solid-state laser architectures and their characteristics

et al. 2022

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The development of high-power diode lasers enabled new solid-state laser concepts such as thin-disk, fiber, and Innoslab lasers based on trivalent ytterbium as the laser-active ion, which resulted in a tremendous increase in the efficiency and beam quality of cw lasers compared to previously used lamp-pumped rod or slab lasers and the realization of ultrafast lasers with several 100 W or even kilowatts of average power. In addition to their beneficial thermo-optical properties, these architectures offer characteristic benefits making them especially suitable to obtain dedicated laser properties. This review article comprises milestone developments, characteristic challenges, and benefits, and summarizes the state of the art of high-power solid-state lasers with the focus on ultrafast lasers.

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Comprehensive Theoretical Study of Mode Instability in High-Power Fiber Lasers by Employing a Universal Model and Its Implications

Cited by 105 publications

References 144 publications

Intensity noise as a driver for transverse mode instability in fiber amplifiers

Intensity noise as a driver for transverse mode instability in fiber amplifiers

High power all-fiberized and narrow-bandwidth MOPA system by tandem pumping strategy for thermally induced mode instability suppression

High-power, high-brightness solid-state laser architectures and their characteristics

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