Suppressing stimulated Raman scattering in kW-level continuous-wave MOPA fiber laser based on long-period fiber gratings

Jiao, Kerong; Shen, Hua; Guan, Zhiwen; Yang, Feiyan; Zhu, Rihong

doi:10.1364/oe.384760

Cited by 39 publications

(19 citation statements)

References 23 publications

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“…Another seed characteristic is the Raman noisy in the seed light. It was found that the Raman noisy can obviously enhance SRS in the high-power Yb-doped fiber amplifiers [18], which can be effectively lowered with the Raman filter such as the tilted fiber Bragg gratings (TFBGs) [15], [26] or long period gratings (LFBGs) [27]- [29]. Furthermore, the seed average power also plays an important role in SRS threshold.…”

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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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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“…These hydrogen molecules and hydroxyl compounds have great infrared absorption ability, resulting in heating or even burning of the PS-LPFG when kilowatt-level power passes through it. To promote the capacity of our PS-LPFG to carry high-power laser, our proposed dual annealing method is adopted [20,23] . The constant-low-temperature annealing (60 • C for 30 days) is applied to volatilize the hydrogen molecules and the dynamic-high-temperature annealing is utilized to make the hydroxyl compounds be evaporated away from the PS-LPFG.…”

Section: Fabricationmentioning

confidence: 99%

“…The experimental results showed that LPFGs can effectively suppress SRS in a pulsed fiber laser. In 2020, we utilized LPFGs to suppress SRS in the seed and amplifier of a kilowatt-level MOPA system separately [23] . It is well known that the distance between the wavelength of the Raman light and the wavelength of signal laser is over dozens of nanometers, which means SRS is an independent spectrum.…”

Section: Introductionmentioning

confidence: 99%

Utilizing phase-shifted long-period fiber grating to suppress spectral broadening of a high-power fiber MOPA laser system

Bian

Jiao

et al. 2021

High Pow Laser Sci Eng

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Suppressing nonlinear effects in high-power fiber lasers based on fiber gratings has become a hotspot. At present, research is mainly focused on suppressing stimulated Raman scattering in a high-power fiber laser. However, the suppression of spectral broadening, caused by self-phase modulation or four-wave mixing, is still a challenging attribute to the close distance between the broadened laser and signal laser. If using a traditional fiber grating with only one stopband to suppress the spectral broadening, the signal power will be stripped simultaneously. Confronting this challenge, we propose a novel method based on phase-shifted long-period fiber grating (PS-LPFG) to suppress spectral broadening in a high-power fiber master oscillator power amplifier (MOPA) laser system in this paper. A PS-LPFG is designed and fabricated on 10/130 passive fiber utilizing a point-by-point scanning technique. The resonant wavelength of the fabricated PS-LPFG is 1080 nm, the full width at half maximum of the passband is 5.48 nm, and stopband extinction exceeds 90%. To evaluate the performance of the PS-LPFG, the grating is inserted into the seed of a kilowatt-level continuous-wave MOPA system. Experiment results show that the 30 dB linewidth of the output spectrum is narrowed by approximately 37.97%, providing an effective and flexible way for optimizing the output linewidth of high-power fiber MOPA laser systems.

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“…Furthermore, LPFGs were applied in temperature or stress detection [ 5 , 6 , 7 , 8 ]. Except for applications in fiber sensors, researchers applied LPFGs as spectral filtering devices in fiber lasers [ 9 , 10 , 11 , 12 ]. For example, LPFGs have been used to suppress the stimulated Raman scattering (SRS) effect in high-power fiber lasers, where core-guided SRS light can be stripped out of the core by inserting LPFGs, and the proportion of signal light in the output terminal can be increased [ 9 , 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

“…Except for applications in fiber sensors, researchers applied LPFGs as spectral filtering devices in fiber lasers [ 9 , 10 , 11 , 12 ]. For example, LPFGs have been used to suppress the stimulated Raman scattering (SRS) effect in high-power fiber lasers, where core-guided SRS light can be stripped out of the core by inserting LPFGs, and the proportion of signal light in the output terminal can be increased [ 9 , 10 , 11 ]. By inscribing LPFGs in an erbium-doped fluoride glass fiber, Heck et al proposed a new concept to mitigate the parasitic laser effect in mid-infrared fiber amplifiers [ 12 ].…”

Section: Introductionmentioning

confidence: 99%

Spectral Characteristics of Square-Wave-Modulated Type II Long-Period Fiber Gratings Inscribed by a Femtosecond Laser

Zhao

Rao

et al. 2021

Sensors

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We study here the spectral characteristics of square-wave-modulated type II long-period fiber gratings (LPFGs) inscribed by a femtosecond laser. Both theoretical and experimental results indicate that higher-order harmonics refractive index (RI) modulation commonly exists together with the fundamental harmonic RI modulation in such LPFGs, and the duty cycle of a square wave has a great influence on the number and amplitudes of higher-order harmonics. A linear increase in the duty cycle in a series of square wave pulses will induce another LPFG with a minor difference in periods, which is useful for expanding the bandwidth of LPFGs. We also propose a method to reduce insertion loss by fabricating type II LPFGs without higher-order harmonic resonances. This work intensifies our comprehension of type II fiber gratings with which novel optical fiber sensors can be fabricated.

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Suppressing stimulated Raman scattering in kW-level continuous-wave MOPA fiber laser based on long-period fiber gratings

Cited by 39 publications

References 23 publications

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

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

Utilizing phase-shifted long-period fiber grating to suppress spectral broadening of a high-power fiber MOPA laser system

Spectral Characteristics of Square-Wave-Modulated Type II Long-Period Fiber Gratings Inscribed by a Femtosecond Laser

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