Effective suppression of the photodarkening effect in high-power Yb-doped fiber amplifiers by H₂ loading

Abstract

The radical suppression of the photodarkening effect and laser performance deterioration via H 2 loading were demonstrated in high-power Yb-doped fiber (YDF) amplifiers. The photodarkening loss at equilibrium was 114.4 dB/m at 702 nm in the pristine fiber, while it vanished in the H 2 -loaded fiber. To obtain a deeper understanding of the impact of photodarkening on laser properties, the evolution of the mode instability threshold and output power in fiber amplifiers was investigated. After pumping for 300 min, the mode instability threshold of the pristine fiber dropped from 770 to 612 W, and the periodic fluctuation of the output power became intense, finally reaching 100 W. To address the detrimental effects originating from photodarkening, H 2 loading was applied in contrast experiments. The output power remained stable, and no sign of mode instability was observed in the H 2 -loaded fiber. Moreover, the transmittance at 638 nm confirmed the absence of the photodarkening effect. The results pave the way for the further development of high-power fiber lasers.

Progress and Summary of Photodarkening in Rare Earth Doped Fiber

“…Compared with the improved conventional vapor deposition method, equilibrium PD-induced excess loss of the nanoporous glass fiber was reduced to 35.07, 12.49, and 1.69 dB/m at 702, 810, and 1041 nm, respectively, despite higher Yb 3+ concentration. In 2020, Cao et al [37] found that in high-power YDF amplifiers, H 2 loading could fundamentally inhibit the deterioration of the optical aging effect and laser performance.…”

Material constraint‐based laser performance estimation of Yb3+‐doped phosphate fibers

“…For simplicity, the transverse fluctuation (D c ) and cross effect (D c L c ) were used as variables. Finally, the estimation of P th and η is obtained in Equations ( 9) and (10). For the function y = f(x i ), a sensitivity analysis was calculated using Equation (12) to assess the effect of the independent variable x i on the dependent variable y.…”

“…Ytterbium ion (Yb 3+ ) has been widely studied as an optimal gain medium for high-power lasers due to its small quantum defect. [1][2][3][4][5][6][7][8][9][10][11][12] Due to the high Yb 3+ solubility, high gain single-frequency laser can be obtained from a Yb 3+ -doped phosphate fiber with a short linear cavity. 13 Thus, improving the laser performance of phosphate fibers is conducive to the miniaturization and integration of optical devices with linear cavity structure.…”

2-kW-level superfluorescent fiber source with flexible wavelength and linewidth tunable characteristics

“…Superfluorescent fiber source (SFS), which originates from the superfluorescent radiation in the gain medium of optical fiber, not only has the advantages of fiber lasers such as high efficiency and high beam quality [1,2], but also inherits the merits of superfluorescent sources such as broadband emission and low coherence [3,4], thus showing great application potential in sensing, spectroscopy, biomedical imaging and so on [5][6][7][8]. Compared with fiber oscillators which have well-defined cavities, SFS shows higher temporal stability while maintaining good power scalability [9,10], so it is pretty suitable for pumping the optical parametric oscillators (OPOs) [11,12] and Raman fiber lasers (RFLs) [13,14].…”