Experimental Study of Output Characteristics of Bi-Directional Pumping High Power Fiber Amplifier in Different Pumping Schemes

Shi, Chen; Su, Rong Tao; Zhang, Han Wei; Yang, Bo; Wang, Xiaotian; Zhang, Pu; Xu, Xiong; Lu, Qinghui

doi:10.1109/jphot.2017.2679753

Cited by 41 publications

(36 citation statements)

References 22 publications

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“…2(c), in which the forward pump power is 1336 W and the backward pump power is 2004 W (the ratio of the backward pump power to the total pump power is ∼60%). It is also noted that the slope efficiency under the counter-pump regime is higher than that under the co-pump and the bi-directional pump regime, which agrees with the reported results [34], [38]. However, with the forward pump power maintained and the backward pump power further increased, the output power continues to increase linearly while the threshold features in temporal and frequency domain are not strengthened.…”

Section: Experimental Investigationssupporting

confidence: 89%

“…For the monolithic fiber laser system, the investigation in experiment scope was less conducted. Shi et al have experimentally demonstrated the enhancement of the TMI threshold by changing pump direction [38], but the TMI threshold under counter-pump regime was proved lower than that under the co-pump regime, which run counter to the existing models and the underlying reason still needed to be explained. Meanwhile, the optimization of the forward and the backward pump allocation in bi-directional pump regime was not investigated in this work, and no theoretical model was provided to support all the experimental results, either.…”

Section: Introductionmentioning

confidence: 88%

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Towards the Enhancement of the TMI Threshold in Monolithic High-Power Fiber System by Controlling the Pump Distribution and the Seed Power

Huang¹,

Tao²,

Shi³

et al. 2018

IEEE Photonics J.

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In recent years, the transverse mode instability (TMI) has been a main limiting factor of average power scalability of high-power fiber lasers with near-diffraction-limited beam quality. A number of strategies in experimental or theoretical scopes have been proposed to mitigate the TMI, especially in the bulk-optic systems. In this paper, the enhancement of the TMI threshold is to be systematically investigated in a monolithic high-power large-modearea (LMA) Yb-doped fiber laser system, by all-optical strategies including optimizing the pump distribution as well as adapting the seed power during operation. It is demonstrated that the TMI threshold can be dramatically increased under counter-pump and bi-directional pump regime compared with the co-pump regime. Further enhancement of the TMI threshold is achieved via optimizing the ratio of the forward pump power to the total pump power under bi-directional pump regime. As a result, a ∼3 kW TMI-free high-power output is realized. Moreover, the systematical study on the effect of the seed laser on the TMI threshold reveals a rising trend of the TMI threshold with the seed power increased. At the same time, a semi-analytical model considering both the gain saturation and the photo-darkening effect is set to theoretically analyze the TMI threshold, manifesting good agreements with the experimental data. This paper provides a valuable reference for the construction of monolithic high-power LMA fiber-based laser system in terms of effectively mitigating the TMI threshold.

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Section: Experimental Investigationssupporting

confidence: 89%

Section: Introductionmentioning

confidence: 88%

Towards the Enhancement of the TMI Threshold in Monolithic High-Power Fiber System by Controlling the Pump Distribution and the Seed Power

Huang¹,

Tao²,

Shi³

et al. 2018

IEEE Photonics J.

Self Cite

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“…Therefore, the seed power should not be too small and its optimization is indispensable in the designation of high-power fiber amplifiers. Moreover, it should be noted that the physical mechanism of weak-seed enhancement of SRS is not dependent on the type of active fiber, and the same phenomenon was witnessed in the double-cladding fiber laser with end-pumping technique [30].…”

Section: Resultsmentioning

confidence: 55%

“…However, Ref. [30] also observed that the Raman light will decrease with the increment of seed power, but no explanation was given. Besides, no other reference was found to report the phenomenon similar to Ref.…”

Section: Introductionmentioning

confidence: 99%

Weak-Seed Induced Enhancement of Stimulated Raman Scattering in Distributed Side-Pumped Yb-Doped Fiber Amplifiers

et al. 2020

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The effect of tens-of-Watt seed light on the stimulated Raman scattering (SRS) in a distributed side-pumped Yb-doped fiber amplifier is studied. By using two sorts of seed sources with the power smaller than 70 W, it is observed in experiment that the SRS can be enhanced by lowering the seed power. To the best of our knowledge, this is the first observation of the weak-seed enhancement of SRS in the distributed side-pumped Ybdoped fiber amplifier. In order to reveal the physical mechanism of the phenomenon, the numerical study is carried out. It is found that the Yb-gain at Raman wavelength, although much smaller than that at signal wavelength (i.e., 1080 nm), plays an important role in the phenomenon. It is also revealed that the weak-seed enhancement of SRS can only be presented when the dopant concentration is large enough (e.g., larger than 3 × 10 25 in our numerical calculation). Besides, with more effective suppression of Raman seed, the weak-seed induced enhancement of SRS could be observed in a larger seed power range. The pertinent results and conclusion can provide significant guidance for designing high-power fiber lasers and amplifiers.

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“…Since the first publication of TMI in fiber laser systems 4 , lots of theoretical and experimental studies have been reported on TMI mitigation strategies 5 – 10 . Some conventional ways to avoid the TMI in high-power laser systems are to use extremely low NA fibers 11 , tight coiling 12 , 13 and controlling the heat load of the gain fiber by making a shift between the pumping wavelength and the gain fiber’s peak absorption wavelength 14 . Concerning the SRS, enlargement of the fiber mode area 15 , decreasing the effective fiber length, and broadening the bandwidth of fiber Bragg gratings (FBGs) 16 are the most common suppressing methods.…”

Section: Introductionmentioning

confidence: 99%

The effect of population inversion saturation on the transverse mode instability threshold in high power fiber laser oscillators

Roohforouz

Chenar

Rezaei-Nasirabad

et al. 2021

Sci Rep

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To achieve a 3.02 kW Yb-doped fiber laser oscillator, the behavior of transverse mode instability (TMI) is experimentally studied in different pumping configurations; co, hybrid, counter, and bidirectional. A comparative analysis showed that population inversion saturation has a substantial impact on TMI threshold enhancement in high power fiber oscillators. Monitoring the dynamic power exchange of fundamental mode and higher-order mode of laser output beam indicates that in a hybrid pumping scheme, simultaneous pumping with two different wavelengths enhances the TMI threshold to a great stand. Moreover, injecting a few watts of pumping light in the counter direction mitigates the TMI caused by pumping in the co-direction. Calculation of population inversion in different pumping configurations using simulation shows that higher population inversion saturation leads to increasing the TMI threshold.

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Experimental Study of Output Characteristics of Bi-Directional Pumping High Power Fiber Amplifier in Different Pumping Schemes

Cited by 41 publications

References 22 publications

Towards the Enhancement of the TMI Threshold in Monolithic High-Power Fiber System by Controlling the Pump Distribution and the Seed Power

Towards the Enhancement of the TMI Threshold in Monolithic High-Power Fiber System by Controlling the Pump Distribution and the Seed Power

Weak-Seed Induced Enhancement of Stimulated Raman Scattering in Distributed Side-Pumped Yb-Doped Fiber Amplifiers

The effect of population inversion saturation on the transverse mode instability threshold in high power fiber laser oscillators

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