Abstract
In this paper, we summarize the research on photodarkening in optical fibers. The causes of photodarkening in fiber, the influence of photodarkening on fiber laser, the experimental device of photodarkening, and the mathematical model used to study the phenomenon of photodarkening are described in detail. At the end of the paper, we summarize the means and methods to suppress photodarkening.
Highlights
Fiber laser has a wide range of application prospects in industrial processing, advanced manufacturing, national defense, and other fields due to its advantages of high efficiency, high stability, high beam quality, and easiness to expand to high power
PD is characterized by broadband absorption centered on the wavelength of visible light, which increases with working time, and the performance of PD is related to the preparation method of active optical fiber [1,2,3,4,5,6,7]
Because the absorption spectrum of the color center generated in the PD process covers the pump band and even the signal band of the fiber laser, the output power and slope efficiency of the fiber laser is significantly reduced
Summary
Fiber laser has a wide range of application prospects in industrial processing, advanced manufacturing, national defense, and other fields due to its advantages of high efficiency, high stability, high beam quality, and easiness to expand to high power. Broer et al [10] found that Tm-doped silica fiber appeared PD when excited by a near-infrared laser (1064 nm) He attributed this phenomenon to ultraviolet and visible light produced by photon avalanche upconversion. Ponsoda et al [26] examined the effect of PD-induced pump light absorption on YDF thermal loading. The results showed that it had good repeatability without an obvious change of glass structure They found that in the process of infrared irradiation, the level of saturation of the PD losses could be determined by the core temperature. In 2020, Cao et al [37] found that in high-power YDF amplifiers, H2 loading could fundamentally inhibit the deterioration of the optical aging effect and laser performance
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