Dy-Al-P codoped silica fiber for visible emission fiber lasers

Pushing light emission from silica-based gain media to shorter wavelengths creates strong competition with photodarkening. To date, rare-earth-doped singly modified silica host glasses have shown excessive defect center absorption. Doubly-modified silica host glasses, however, could offer fewer intrinsic point defects and less induced absorption, but few studies on this subject exist. In this report, Dy³⁺-doped alumino-phospho-silica (APS) glass fiber lasers pumped with 450 nm GaN diode lasers have been examined. The benefits of a low background loss on the efficiency are shown, providing a record slope efficiency of 24% using a 30% output coupler. The decline in the output power from photodarkening over time has also been examined in detail. It is shown that the development of doubly-modified silica host glass systems shows promise in lowering the degree and rate of photodarkening, which is also supported by a survey of the available literature.