High-speed modal decomposition of mode instabilities in high-power fiber lasers

Stutzki, Fabian; Otto, Hans-Jürgen; Jansen, Florian; Gaida, Christian; Jáuregui, César; Limpert, Jens; Tünnermann, Andreas

doi:10.1364/ol.36.004572

Cited by 147 publications

(75 citation statements)

References 12 publications

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“…We also note that a complete transfer between the modes can occur on a sub-ms timescale. Such a complete transfer of power between the modes has been experimentally observed in [3].…”

Section: Operation Beyond Thresholdmentioning

confidence: 67%

“…The phenomenon manifests itself as a temporal fluctuation, typically on a ms timescale, of the output beam profile as the output power reaches a certain threshold. Detailed experimental investigations of TMI have shown that the power and relative phase of the light in the fundamental and higher-order modes of the amplifier fluctuates on a timescale which depends strongly on the core diameter of the fiber, and that only the first higher-order mode (HOM) is involved, except for fibers with very large core diameters [3,4]. While the onset of TMI does not in itself prevent the amplification of the signal beyond the instability threshold, the resulting dramatic decrease in beam quality renders the amplifier useless for applications that require a stable output beam.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical analysis of mode instability in high-power fiber amplifiers

Hansen¹,

Alkeskjold²,

Broeng³

et al. 2013

Opt. Express

161

133

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We present a simple theoretical model of transverse mode instability in high-power rare-earth doped fiber amplifiers. The model shows that efficient power transfer between the fundamental and higher-order modes of the fiber can be induced by a nonlinear interaction mediated through the thermo-optic effect, leading to transverse mode instability. The temporal and spectral characteristics of the instability dynamics are investigated, and it is shown that the instability can be seeded by both quantum noise and signal intensity noise, while pure phase noise of the signal does not induce instability. It is also shown that the presence of a small harmonic amplitude modulation of the signal can lead to generation of higher harmonics in the output intensity when operating near the instability threshold.

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“…We also note that a complete transfer between the modes can occur on a sub-ms timescale. Such a complete transfer of power between the modes has been experimentally observed in [3].…”

Section: Operation Beyond Thresholdmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of mode instability in high-power fiber amplifiers

Hansen¹,

Alkeskjold²,

Broeng³

et al. 2013

Opt. Express

161

133

View full text Add to dashboard Cite

show abstract

“…Thus, this temporally segmented and collated representation of one-dimensional intensity dynamics is called the spatio-temporal evolution of laser intensity, or simply, spatio-temporal dynamics [32,33] (also see Supplementary, [33]). In a broader context, spatio-temporal representations of intensity dynamics have been employed in describing the dynamic behaviour of semiconductor lasers [34,35] including vertical cavity surface emitting lasers [36,37], transverse pattern formation in various lasers and parametric oscillators [38,39], in the study of multimode instabilities [40][41][42], including those observed in high power fibre lasers [43,44] and in the influence of stimulated Brillouin scattering [45,46]. Spatio-temporal representations of intensity evolution have also been routinely used in the numerical modelling of various kinds of fibre-based light sources [47][48][49].…”

Section: Principlementioning

confidence: 99%

Real-Time Intensity Domain Characterization of Fibre Lasers Using Spatio-Temporal Dynamics

2016

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Fibre lasers are light sources that are synonymous with stability. They can give rise to highly coherent continuous-wave radiation, or a stable train of mode locked pulses with well-defined characteristics. However, they can also exhibit an exceedingly diverse range of nonlinear operational regimes spanning a multi-dimensional parameter space. The complex nature of the dynamics poses significant challenges in the theoretical and experimental studies of such systems. Here, we demonstrate how the real-time experimental methodology of spatio-temporal dynamics can be used to unambiguously identify and discern between such highly complex lasing regimes. This two-dimensional representation of laser intensity allows the identification and tracking of individual features embedded in the radiation as they make round-trip circulations inside the cavity. The salient features of this methodology are highlighted by its application to the case of Raman fibre lasers and a partially mode locked ring fibre laser operating in the normal dispersion regime.

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“…3. Using the modal decomposition method [19][20][21], the power ratios of the four lower modes (LP01, LP11, LP21, and LP02) in the amplifier are estimated to be 44.92 %, 37.8 %, 14.04 %, and 3.24 %, respectively. The result indicates that the beam quality is not very good compared with a fundamental mode laser.…”

Section: Sbs Suppression Of Three-tone Seeded Fiber Amplifiermentioning

confidence: 99%

1.8-kW simultaneous spectral and coherent combining of three-tone nine-channel all-fiber amplifier array

et al. 2012

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We demonstrate simultaneous spectral and coherent combining of a three-tone nine-channel all-fiber amplifier array with a total output power of 1.8 kW in a master-oscillator power-amplifier (MOPA) configuration. Three single-frequency seed lasers are spectrally combined and employed as a master oscillator for an all-fiber power amplifier array, which provides robust performance on suppressing of the stimulated Brillouin scattering effect. Threestage power amplifiers are employed to scale the power from tens of mW to more than 300 W. Active phase locking of the nine-channel spectrally combined amplifiers is implemented by using the stochastic parallel gradient descent algorithm. In the experiment, a nine-channel spectrally combined MOPA array is coherently combined with a total output power of 1.8 kW. The power in the main lobe in closed loop is 4.6 times the value in open loop, and an average visibility of more than 85 % of the interference pattern at the receiving plane is obtained. By only adding pump power in the main amplifiers, the total power of the array could scale up to more than 3 kW.

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High-speed modal decomposition of mode instabilities in high-power fiber lasers

Cited by 147 publications

References 12 publications

Theoretical analysis of mode instability in high-power fiber amplifiers

Theoretical analysis of mode instability in high-power fiber amplifiers

Real-Time Intensity Domain Characterization of Fibre Lasers Using Spatio-Temporal Dynamics

1.8-kW simultaneous spectral and coherent combining of three-tone nine-channel all-fiber amplifier array

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