Suppressing mode instabilities by optimizing the fiber coiling methods

Self Cite

Compared with traditional uniform fibers, tapered fiber has numerous unique advantages, such as larger mode area, higher pump absorption, suppression to nonlinear effects, and maintaining good beam quality. In this manuscript, we have constructed an all-fiberized fiber amplifier which is based on a piece of ytterbium-doped tapered double-clad fiber (T-DCF). The fiber amplifier is operated under continuous wave (CW) regime at 1080 nm wavelength. The $M^{2}$ factor of the amplifier at 1.39 kW output power is ${\sim}1.8$. The maximum output power of the system reached 1.47 kW, which, to the best of our knowledge, is the highest output power of long tapered fiber based fiber laser system. Our result successfully verifies the potential of power scalability and all-fiberized capability of long tapered fiber, and the performance of our system can be further enhanced by fiber design optimization.

Section: Resultssupporting

confidence: 86%

kW-class high power fiber laser enabled by active long tapered fiber

Shi

Zhang

Wang

et al. 2018

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“…We want to stress that nearly single transverse-mode-amplified light can be acquired via effective high-order transverse-mode management despite the employment of non-strict-single-mode YDF in the main amplification stage. In the power amplification, the coil diameter is optimized to be about 15 cm [42][43][44] . Then total bending loss of about 18 dB can be obtained for the LP 11 mode in the 30 m long YDF, while the bending loss for LP 01 mode can be neglected.…”

Section: Resultsmentioning

confidence: 99%

In-band pumping avenue based high power superfluorescent fiber source with record power and near-diffraction-limited beam quality

et al. 2018

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High power superfluorescent fiber sources (SFSs), which could find wide applications in many fields such as middle infrared laser generation, Raman fiber laser pumping and spectral beam combination, have experienced a flourishing time in recent years for its unique properties, such as short coherence length and high temporal stability. The challenge for performance scalability of powerful SFS mainly lies on the physical issues including parasitic laser oscillation and modal instability (MI). In this contribution, by employing in-band pumping avenue and high-order transverse-mode management, we explore a high power SFS with record power, near-diffraction-limited beam quality and spectral manipulation flexibility. An ultimate output power of 3.14 kW can be obtained with high temporal stability and a beam quality of M 2 = 1.59 for the amplified light. Furthermore, the dynamics of spectral evolutions, including redshifting of central wavelength and unsymmetrical broadening in spectral wings, of the main amplifier with different seed linewidths are investigated contrastively. Benefiting from the unique high pump brightness and high MI threshold of in-band pumping scheme, the demonstrated system also manifests promising performance scaling potential.

“…For the TMI in the coiled fiber, A. V. Smith and J. J. Smith proposed the BPM model which considers a preset mode loss [16] . Tao et al proposed a semi-analytical model [17] based on the mode bending loss calculated by the Marcuse's formula [18] . However, these models do not consider the thermally induced mode bending loss decrease [19,20] .…”

Section: Introductionmentioning

confidence: 99%

Numerical modeling of the thermally induced core laser leakage in high power co-pumped ytterbium doped fiber amplifier

Kong

Leng

Zhang

et al. 2018

Self Cite

We propose a novel model to explain the physical process of the thermally induced core laser leakage (TICLL) effect in a high power co-pumped ytterbium doped fiber (YDF) amplifier. This model considers the thermally induced mode bending loss decrease and the thermally induced mode instability (TMI) in the coiled YDF, and is further used to reproduce the TICLL effect in the high power co-pumped step-index $20/400$ fiber amplifier. Besides, the TICLL effect in the co-pumping scheme and counter-pumping scheme is compared. The result proves that the TICLL effect is caused by the combined effect of the thermally induced mode bending loss decrease and the TMI, and could be mitigated by adopting the counter-pumping scheme. To our best knowledge, this is the first theoretical explanation of the TICLL effect in high power fiber amplifier.