Controlling mode instability in a 500 W ytterbium-doped fiber laser

Hejaz, Kamran; Norouzey, A; Poozesh, Reza; Heidariazar, Amir; Roohforouz, Ali; Nasirabad, R Rezaei; Jafari, Niloofar; Golshan, Ali Hamedani; Babazadeh, Amin; Lafouti, Majid

doi:10.1088/1054-660x/24/2/025102

Cited by 74 publications

(56 citation statements)

References 14 publications

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“…It includes to reduce pump absorption level by modifying the fiber design. Until now, the influence of various fiber laser parameters on MI, such as pump wavelength, pump directions, signal wavelength, core/cladding radio have been studied theoretically and experimentally. However, from our knowledge, no strategy or experiment about reducing the pump absorption level by broadening the pump linewidth has ever been reported until now.…”

Section: Introductionmentioning

confidence: 99%

Research of the Mode Instability Threshold in High Power Double Cladding Yb‐doped Fiber Amplifiers

Wang¹,

Liu

Ma³

et al. 2017

Annalen der Physik

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We experimentally investigate the behavior of the mode instability (MI) threshold in the double cladding Yb-doped fiber amplifier when the amplifier is pumped by broad linewidth laser diodes and narrow linewidth laser diodes respectively. It is found that the MI threshold increases by 26% when the amplifier is pumped by the broad linewidth laser diodes. Experiment results show that the MI threshold is affected by the local heat load rather than the average or the total heat load. The calculation shows that the local heat deposit actually plays the key role to stimulate the MI behaviour. At the MI threshold position in the fiber, the local heat deposit also changes dramatically. The effect of the thermal conductivity on the MI threshold is also studied. Our investigation shows that the MI threshold increases from 1269 W to 1950 W when the thermal conductivity of the fiber amplifier is increased from 0.3 W/(m · K) to 5 W/(m · K). Through optimizing the pump linewidth and the cooling efficiency of the gain fiber, the MI threshold is doubled in our experiment.

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Section: Introductionmentioning

confidence: 99%

Research of the Mode Instability Threshold in High Power Double Cladding Yb‐doped Fiber Amplifiers

Wang¹,

Liu

Ma³

et al. 2017

Annalen der Physik

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“…Based on numerical simulations, some mitigation strategies have already been suggested, for example, reducing the heat load [7] or saturating the gain of the amplifier [8]. Also, experimental methods for increasing the MI threshold have been presented: The MI threshold could be increased by changing the pump wavelength [9] and by dynamically exciting modes at the fiber input with an acousto-optic deflector [10].…”

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confidence: 99%

Optimizing mode instability in low-NA fibers by passive strategies

et al. 2015

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Systematic experimental investigations toward the mode instability (MI) threshold in low-NA fibers are performed. By testing several fibers with varying V-parameters drawn from the same preform, a high degree of reproducibility of the experimental conditions could be achieved. This allows for systematic investigations on isolated parameters influencing the complex behavior of MI. A maximum MI threshold of 2 kW could be demonstrated for the tested fibers, which represents a new record output power for narrow linewidth fiber amplifiers. The MI threshold was found to sensitively depend on the V-parameter for large V-parameters (>2), but to be robust for smaller V-parameters. Furthermore, the fiber bending diameter and the seed excitation conditions were identified to sensitively influence the MI threshold.

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“…the pump wavelength and coiling the fiber for HOM suppression [18]. The instability threshold was determined from the slope efficiency curve, and so its nature (static/dynamic) is not entirely clear from the results presented.…”

Section: Comparison To Experimental Resultsmentioning

confidence: 99%

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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Controlling mode instability in a 500 W ytterbium-doped fiber laser

Cited by 74 publications

References 14 publications

Research of the Mode Instability Threshold in High Power Double Cladding Yb‐doped Fiber Amplifiers

Research of the Mode Instability Threshold in High Power Double Cladding Yb‐doped Fiber Amplifiers

Optimizing mode instability in low-NA fibers by passive strategies

Static thermo-optic instability in double-pass fiber amplifiers

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