Influence of Aberrations on Modal Decomposition for LMA Fiber Laser Systems

Chai, Junyu; Liu, Wenguang; Zhang, Jiangbin; Xie, Kang; Lu, Yao; Li, Changjin; Liu, Pengfei; Zhou, Qiong; Jiang, Zongfu; Zhao, Guangyao

doi:10.3389/fphy.2021.796666

Cited by 3 publications

(2 citation statements)

References 32 publications

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“…The ratios of the intensities at sub-optical axes represent the modal coefficients I ∞ |c n | 2 . Thus, the modal weight can be directly accessible via a simple intensity measurement to investigate the modal coupling [23].…”

Section: The MD Based On Ocfmentioning

confidence: 99%

High-speed modal analysis of dynamic modal coupling in fiber laser oscillator

et al. 2023

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Up till now, the spatial and temporal dynamics of transverse mode instability (TMI) in fiber laser oscillator have increasingly attracted a worldwide attention. Here, we develop a high-speed modal decomposition (MD) system to analyze the modal coupling for fiber laser oscillator above the TMI threshold. A set of angular-multiplexing transmission functions (TFs) are designed for simultaneous MD and monitoring the far-field beam profile. The TMI threshold of the deployed fiber laser oscillator is 181 W at a co-pumping power (CPP) of 279 W. As the CPP increases from 318 W to 397 W, the power fluctuations of the output laser become more drastic. The changes of the far-field beam profile and the centroid of far-field spot (COFFS) indicate an increased velocity of energy transfer between modes. The high-speed MD verifies above process and analyzes the modal components, indicating that the single cycle of modal coupling decreases from 11 ms to 4 ms. Otherwise, the strong mode coupling occurs between modes with relatively large weights. The high-speed MD provides a powerful tool to research the TMI effect.

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Section: The MD Based On Ocfmentioning

confidence: 99%

High-speed modal analysis of dynamic modal coupling in fiber laser oscillator

et al. 2023

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“…These mitigation strategies using passive optical devices are promising, but are only applicable in specific operation regimes [34]. Considering the physical origin of TMI (dynamic in nature) and taking the idea from adaptive optics, active mode control in a closed-loop system may provide a universal way to stabilize the beam beyond TMI threshold [35]. In principle, active mode control aims to control the direction of mode coupling, allowing energy transfer to flow between fundamental mode and higher-order modes.…”

Section: Introductionmentioning

confidence: 99%

Dynamic modal characteristics of transverse mode instabilities in ytterbium-doped fiber laser oscillator

et al. 2023

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In recent years, transverse mode instability (TMI) has been widely observed in fiber laser amplifier systems. The transverse mode instability phenomenon in fiber laser oscillators is less studied. Here, we focus on the dynamical output properties, i.e., its temporal signal and modal characteristics in a 30-μm-core-diameter ytterbium (Yb)-doped fiber laser oscillator. The TMI occurs at a pumping power around 310 W. Different from amplifiers, the basic oscillation frequency is quite low, at around 100 Hz, changing with time and pump power. When the fiber laser oscillator operates beyond TMI threshold at 357 W or 377 W for a while, the temporal fluctuation slowly disappears together with a decreased oscillation frequency, and appears again later. Based on the mode decomposition technique, we find that during the period of fluctuation disappearance at 357 W, the power output stays low and the output beam is still a mixture of fundamental mode and higher-order modes. The fundamental mode content is calculated to be averagely higher when temporal fluctuation disappears, increasing from ∼57% to ∼63%. Our results indicate complex interaction between the fiber laser oscillation and the TMI effect, and calls for more attention into understanding TMI in fiber laser oscillators.

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Mode decomposition of a few-mode fiber with OAM eigenmodes

Chai

et al. 2022

2nd International Conference on Laser, Optics and Optoelectronic Technology (LOPET 2022)

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Influence of Aberrations on Modal Decomposition for LMA Fiber Laser Systems

Cited by 3 publications

References 32 publications

High-speed modal analysis of dynamic modal coupling in fiber laser oscillator

High-speed modal analysis of dynamic modal coupling in fiber laser oscillator

Dynamic modal characteristics of transverse mode instabilities in ytterbium-doped fiber laser oscillator

Mode decomposition of a few-mode fiber with OAM eigenmodes

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