Emission improvement of Pr-doped silica optical fiber in O-band via Al ions doping

Targeting the O-band telecommunication with low dispersion, Pr-doped silica optical fibers have been demonstrated in this study. First, two local structure models of Pr-3MR (three-membered rings) and Pr/Al-3MR in the silica fiber materials were built up and theoretically analyzed with time-dependent density-functional theory (TDDFT). The simulated results indicated that the fluorescence intensity of Pr/Al-3MR model is enhanced 28% in the O-band, which is probably the result from the reduction of the ground state absorption (GSA), the local phonon energy and the nonradiative decay of Pr³⁺. Then, two kinds of praseodymium (Pr)-doped silica fibers (PDFs) with and without Al³⁺ doping were fabricated using atomic layer deposition (ALD), combined with modified chemical vapor deposition (MCVD). Under 808 nm laser pumping, the typical fluorescence spectrum of the Pr/Al co-doped fiber peaking at 1316 nm was obviously observed in the O-band. The on-off gain is up to 7.35 dB @ 1315 nm with a gain coefficient of up to 0.104 dB/mW. In particular, there is a net gain of approximately 2.08 dB @ 1320 nm. To the best of our knowledge, it is the first report of O-band amplification observed in Pr-doped silica optical fibers. The results indicate that Pr-doped silica fiber can be used for Pr-doped fiber amplifiers and lasers, and PDF has potential applications in the O-band optical communication systems.