Low-threshold mode instability in Yb<sup>3+</sup>-doped few-mode fiber amplifiers: influence of a backward reflection

Антипов, О.Л.; Кузнецов, М. С.; Tyrtyshnyy, V. A.; Alekseev, Dmitry; Vershinin, O.

doi:10.1117/12.2218265

Cited by 4 publications

(4 citation statements)

References 11 publications

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“…In a first attempt, a starting guess for a 1− (0), a 2− (0) was chosen, the equations were propagated forward from z=0 to z=L using a fourth-order Runge-Kutta (RK4) method [13], a 1− (L) and a 2− (L) were set from the resulting values of a 1+ (L), a 2+ (L) using Eq. (17), and the equations were propagated backwards from z=L to z=0. The resulting values for a 1− (0), a 2− (0) were used as starting points for a new pass and the procedure was iterated until a converged solution was obtained.…”

Section: Numerical Results and Discussionmentioning

confidence: 99%

“…Jauregui et al mentioned experiments finding a factor-of-two reduction of the modal instability threshold in bidirectional fiber amplifiers, but did not provide details on the nature of the instability [16]. In a very recent publication [17], Antipov et al showed experimental evidence of a strongly reduced dynamic modal instability threshold in a single-pass amplifier caused by back-reflections from the amplifier end facet. These authors also presented a detailed model, having many similarities with the present work, although focusing on dynamical instabilities and low back-reflection coefficients.…”

Section: Comparison To Experimental Resultsmentioning

confidence: 99%

“…(10)- (13) and (15) from z=0 to z=L lead to final amplitudes satisfying Eq. (17). This is in general a nontrivial task, as will be discussed in the next section.…”

Section: Formal Theorymentioning

confidence: 96%

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Static thermo-optic instability in double-pass fiber amplifiers

Lægsgaard¹

2016

Opt. Express

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A coupled-mode formalism, earlier used to describe transverse mode instabilities in single-pass optical fiber amplifiers is extended to the case of double-pass amplifiers. Contrary to the single-pass case, it is shown that the thermo-optic nonlinearity can couple light at the same frequency between the LP₀₁ and LP₁₁ modes, leading to a static deformation of the output beam profile. This novel phenomenon is caused by the interaction of light propagating in either direction with thermo-optic index perturbations caused by light propagating in the opposite direction. The threshold power for the static deformation is found to be several times lower than what is typically found for the dynamic modal instabilities observed in single-pass amplifiers.

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Section: Numerical Results and Discussionmentioning

confidence: 99%

Section: Comparison To Experimental Resultsmentioning

confidence: 99%

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Static thermo-optic instability in double-pass fiber amplifiers

Lægsgaard¹

2016

Opt. Express

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“…Researchers find that MI thresholds decrease dramatically in the presence of a backward reflection of signal from the output fiber end or an external counter-propagating beam. As thermal grating is recognized as the main mechanism of MI in large-mode area fibers, the population (electronic) grating [43] could be the dominant mechanism for the low-threshold MI effect in the few-mode fibers.…”

Section: Mode Instabilitymentioning

confidence: 99%

Development and prospect of high-power doped fibers

Wang

Chen

2018

High Pow Laser Sci Eng

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Ytterbium-doped fibers have become the optimum gain media of high-power fiber lasers thanks to a simple energy structure, which strongly reduces the excited state absorption, and a low quantum defect and a high optic-optic conversion efficiency, which means the low thermal load. In this paper, we take a review of the current state of the art in terms of Yb 3+ doped fibers for high-power fiber lasers, including the development of the fabrication techniques. The research work to overcome the challenges for Yb 3+ doped fibers, which affect the stability of output power and beam quality, will be demonstrated. Direction of further research is presented and the goal is to look for a fiber design, to boost single fiber output power, stabilize the laser power and support robust single-mode operation.

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Experimental study of the influence of mode excitation on mode instability in high power fiber amplifier

Chu

Tao

et al. 2019

Sci Rep

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Mode instability with different mode excitation has been investigated by off-splicing the fusion point in a 4 kW-level monolithic fiber laser system, which reveals that the fiber systems exciting more high order mode content exhibits lower beam quality but higher mode instability threshold. The static-to-dynamic mode degradation and dynamic-only mode degradation have also been observed in the same high power fiber amplifier by varying the mode excitation, which implicates that the mode excitation plays an important role in mode characteristics in high power fiber lasers. By employing a seed with near fundamental mode beam quality, only dynamic mode degradation-mode instability sets in with negligible static beam quality degradation. Then the fusion point in the seed laser is offset spliced to excite high order mode. As the output power of the main amplifier scales, the beam quality degrades with the beam profile being static, and then the dynamic mode instability sets in, the power threshold of which is higher than that with good beam quality seed. We consider that the static mode degradation is caused by the presence of incoherent supposition of fundamental and high order mode, which leads to that the measured dynamic mode instability threshold is higher.

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Low-threshold mode instability in Yb³⁺-doped few-mode fiber amplifiers: influence of a backward reflection

Cited by 4 publications

References 11 publications

Static thermo-optic instability in double-pass fiber amplifiers

Static thermo-optic instability in double-pass fiber amplifiers

Development and prospect of high-power doped fibers

Experimental study of the influence of mode excitation on mode instability in high power fiber amplifier

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Low-threshold mode instability in Yb3+-doped few-mode fiber amplifiers: influence of a backward reflection

Cited by 4 publications

References 11 publications

Static thermo-optic instability in double-pass fiber amplifiers

Static thermo-optic instability in double-pass fiber amplifiers

Development and prospect of high-power doped fibers

Experimental study of the influence of mode excitation on mode instability in high power fiber amplifier

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Product

Resources

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Low-threshold mode instability in Yb³⁺-doped few-mode fiber amplifiers: influence of a backward reflection