315  kW direct diode-pumped near diffraction-limited all-fiber-integrated fiber laser

Yu, Hailong; Zhang, Hanwei; Lv, Hualiang; Wang, Xiaolin; Leng, Jinyong; Hu, Xiao; Guo, Shan; Zhang, Pu; Xu, Xiaojun; Chen, Jinbao

doi:10.1364/ao.54.004556

Cited by 70 publications

(30 citation statements)

References 16 publications

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“…The rapid progress of high-brightness laser diodes (LDs) and large-mode-area (LMA) fiber fabrication technology quickly pushed the CW fiber laser power to exceed 20 kW in a multimode fiber [15][16][17][18][19][20]. However, such trend was prohibited by a thermo-optical effect called transverse mode instability (TMI).…”

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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Section: Introductionmentioning

confidence: 99%

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

et al. 2023

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“…Typical LMA fibers used in the CW laser operation have core diameters of 20-40 µm and an NA of < 0.09 [23][24][25][26][27]. High output power of > 200 W in the CW laser operation has been reported using cladding-pumped Yb-doped and/or Nd+Yb-doped LMA fibers [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. On the other hand, it is extremely challenging to increase the fiber core size while retaining the excellent beam quality because fibers with large core size allow propagation of several transversal modes, except for the fundamental mode (FM).…”

Section: Introductionmentioning

confidence: 99%

Fiber Fuse Simulation in Double-Clad Fibers for High-Power Fiber Lasers

Shuto¹

2022

JEEE

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Rare-earth-doped optical fibers are one of the most promising solid-state lasers. In these fiber lasers, a cladding-pumping scheme using double-clad fibers is utilized to increase the overall conversion efficiency of pumping light. To maintain acceptable beam quality, the low-numerical aperture large-mode-area fibers is effective for the double-clad fibers because the effects of stimulated Raman scattering can be reduced via the corresponding reduction in the power density in the large fiber core. For the large-mode-area double-clad fibers, fiber fuse propagation was investigated theoretically by the explicit finite-difference method using the thermochemical SiO x production model. In the calculation, we assumed the fiber to be in an atmosphere and that part (40 µm in length) of the core was heated to a temperature of 2,923 K. The threshold power for the double-clad fiber with the core radius of 10 µm was 1.6 W at 1.080 µm and it was close to the experimental value. The power dependence of the velocity of fiber fuse propagation was calculated for the double-clad fibers with the core radius of 10 and 15 µm. The calculated velocities were in fair agreement with the experimental values observed in the input power range from 1 kW to 3.5 kW at 1.080 µm.

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“…Typical LMA fibers used in the CW laser operation have core diameters of 20-40 µm and a numerical aperture (NA) of < 0.09 [10][11][12][13][14]. High output power of > 200 W in the CW laser operation has been reported using cladding-pumped Yb-doped and/or Nd-and Yb-codoped LMA fibers [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Bending Induced Temperature Increases in Double-Clad Fibers for High-Power Fiber Lasers

Shuto¹

2022

JEEE

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Rare-earth-doped optical fibers are one of the most promising solid-state lasers. In these fiber lasers, a cladding-pumping scheme using large-mode-area double-clad fibers (DCFs) is utilized to increase the overall conversion efficiency of pumping light and to overcome the restriction owing to the onset of stimulated Raman scattering. On the other hand, it is extremely challenging to increase the fiber core size while retaining the excellent beam quality because fibers with large core size allow propagation of several higher-order modes (HOMs), except for the fundamental mode (FM). In order to suppress HOMs, DCFs are bent with a relatively small bend radius. Failures at bends in an optical fiber are caused by light leaking from the core when the fiber is accidentally bent tightly with a high power input. For the DCFs with core radii of 10 and 20 µm, the relationship between the bending induced temperature increases and the bend losses in the bent DCFs was investigated theoretically by the explicit finite-difference method using the thermochemical SiO x production model. The temperature at the boundary between the inner and outer cladding layers increased with increasing optical power P at 1.080 µm and was a large value higher than the softening temperature T s of the silica glass when P = 5 kW was entered to the bent DCF with a bend radius R of 150 mm and a core radius of 10 µm. On the other hand, the temperature at the boundary was a small value lower than the T s when P = 10 kW was entered to the bent DCF with a large R of 245-275 mm. Furthermore, it was found that the initiation of the fiber fuse was fairly easy under a certain conditions where the temperature at the boundary was higher than the T s .

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315 kW direct diode-pumped near diffraction-limited all-fiber-integrated fiber laser

Cited by 70 publications

References 16 publications

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

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

Fiber Fuse Simulation in Double-Clad Fibers for High-Power Fiber Lasers

Bending Induced Temperature Increases in Double-Clad Fibers for High-Power Fiber Lasers

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