3.05 kW monolithic fiber laser oscillator with simultaneous optimizations of stimulated Raman scattering and transverse mode instability

Yang, Baolai; Zhang, Hanwei; Shi, Chen; Tao, Rumao; Su, Rongtao; Ma, Pengfei; Wang, Xiaolin; Zhang, Pu; Xu, Xiaojun; Lu, Qin

doi:10.1088/2040-8986/aa9ec0

Cited by 49 publications

(29 citation statements)

References 27 publications

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“…The first notable peak of fluctuations emerges at 270 Hz, in the Fourier spectrum. Usually, the characteristic frequencies of the time-domain just at the TMI threshold range from 100 Hz to kHz based on the laser parameters and configurations 5 , 21 , 26 , 27 . In amplifiers, most reported frequencies are in the order of kHz and for oscillators, they are usually in the order of hundreds of Hz 28 .…”

Section: Resultsmentioning

confidence: 99%

“…To enhance the TMI threshold of oscillators the effect of pumping direction and wavelength have been noticed 12 , 14 , 19 , 20 . The advantage of counter-pumping to co-pumping in TMI threshold enhancement has been shown theoretically and experimentally 21 , 22 . Regarding the bi-directional pumping scheme, the TMI threshold is higher than co and counter pumping 12 .…”

Section: Introductionmentioning

confidence: 97%

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The effect of population inversion saturation on the transverse mode instability threshold in high power fiber laser oscillators

Roohforouz

Chenar

Rezaei-Nasirabad

et al. 2021

Sci Rep

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To achieve a 3.02 kW Yb-doped fiber laser oscillator, the behavior of transverse mode instability (TMI) is experimentally studied in different pumping configurations; co, hybrid, counter, and bidirectional. A comparative analysis showed that population inversion saturation has a substantial impact on TMI threshold enhancement in high power fiber oscillators. Monitoring the dynamic power exchange of fundamental mode and higher-order mode of laser output beam indicates that in a hybrid pumping scheme, simultaneous pumping with two different wavelengths enhances the TMI threshold to a great stand. Moreover, injecting a few watts of pumping light in the counter direction mitigates the TMI caused by pumping in the co-direction. Calculation of population inversion in different pumping configurations using simulation shows that higher population inversion saturation leads to increasing the TMI threshold.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

The effect of population inversion saturation on the transverse mode instability threshold in high power fiber laser oscillators

Roohforouz

Chenar

Rezaei-Nasirabad

et al. 2021

Sci Rep

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show abstract

“…When the output power reaches 3.56 kW, periodic fluctuation of the temporal signal is observed, and a special frequency component at ∼2.5 kHz appears in the Fourier spectra. According to the previous works on the TMI in the fiber oscillators [9], [12], the special coupling frequency may relate to the start-up of TMI, because the coupled high-order modes (HOMs) leak into the fiber inner cladding and get stripped out by the CLS. Further increasing the output power to 3.58 kW, the fluctuation grows more intense in the time domain and the coupling frequencies are more apparent.…”

Section: Laser Performance With External Feedbackmentioning

confidence: 99%

Experimental Study of 5-kW High-Stability Monolithic Fiber Laser Oscillator With or Without External Feedback

Shi

et al. 2019

IEEE Photonics J.

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In this paper, we construct a high power monolithic fiber laser oscillator based on a commercial ytterbium-doped fiber with core/inner cladding diameter of 25/400 µm. The output performances of the fiber oscillator are experimentally investigated in the conditions of either with or without an external feedback. In the presence of external feedback, a very strong stimulated Raman scattering (SRS) (∼9 dB below the signal light) emerges at the output power of ∼3.56 kW, where the onset of the transverse mode instability (TMI) limits further power scaling. By large angle cleaving the signal arm of the forward combiner to avoid external feedback, the maximum output power of 5.07 kW is achieved with no sign of TMI. The Raman stokes light is ∼35 dB below the signal light and the M 2 factor is measured to be ∼1.6. To directly characterize its power stability and engineering capability, the fiber oscillator is tested for continuous 5-h operation at ∼5.07 kW with power fluctuation less than 0.42%. During the test process, the output power, spectrum, beam quality, and temporal signal perform excellent stability. The experimental results reveal that thresholds of SRS and TMI strongly depend on the external feedback in high power fiber oscillators.

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“…Generally, a high-power fiber laser can be achieved based on two structures: the master oscillator power amplification (MOPA) structure and the monolithic fiber laser oscillator structure. Compared with the MOPA structure, monolithic fiber laser oscillators enjoy the advantages of a simpler structure, fewer components, and easier operation [20]. However, fibercore temperature measurement in a fiber laser oscillator by OFDR is more difficult than that in the MOPA structure H because the cavity in the oscillator causes stronger backward lasers, which could reduce the signal-to-noise ratio in the measurement system.…”

Section: Introductionmentioning

confidence: 99%

Realization of in Situ Fiber-Core Temperature Measurement in a Kilowatt-Level Fiber Laser Oscillator: Design and Optimization of the Method Based on OFDR

Lou

Han

Yang

et al. 2021

J. Lightwave Technol.

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High-power fiber lasers have been widely used in various industrial manufacturing and military defense applications. During the development of fiber lasers in the past decades, the thermal effect has always been one of the biggest obstacles. It is crucial to study the temperature characteristics and overcome the thermal restrictions for a better output performance. With the systematic design and optimization in this paper, optical frequency domain reflectometry (OFDR) can achieve in situ distributed temperature measurement of the fiber core in highpower fiber lasers. This allows a better study of the temperature characteristics and thermal effects. The fiber-core distributed temperature of a kilowatt-level fiber oscillator is first demonstrated based on this method here. The splicing point between the high reflectivity fiber Bragg grating (HR-FBG) and gain fiber withstands the highest temperature, reaching 101.6 ℃ at a 1.47 kW output. In addition, the temperature of the gain fiber gradually decreases from 92 ℃ to 30 ℃ along the pumping direction. The internal temperatures of the combiner and HR-FBG are also measured to evaluate their performances in the highpower regime. The temperature distributions in the experiment agree well with the theoretical simulation.

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3.05 kW monolithic fiber laser oscillator with simultaneous optimizations of stimulated Raman scattering and transverse mode instability

Cited by 49 publications

References 27 publications

The effect of population inversion saturation on the transverse mode instability threshold in high power fiber laser oscillators

The effect of population inversion saturation on the transverse mode instability threshold in high power fiber laser oscillators

Experimental Study of 5-kW High-Stability Monolithic Fiber Laser Oscillator With or Without External Feedback

Realization of in Situ Fiber-Core Temperature Measurement in a Kilowatt-Level Fiber Laser Oscillator: Design and Optimization of the Method Based on OFDR

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