Upconversion mechanisms of a praseodymium-doped fluoride fibre amplifier

Abstract

We develop a simple method leading to the determination of important parameters for the praseodymium-doped fluoride fibre amplifier (PDFFA), such as the non-radiative energy transfer upconversion coefficient or pump-excited state absorption cross section . We apply this method to five ZBLAN bulks of different concentration (from 10 000 down to 500 wt ppm) and to a ZBLAN: 500 wt ppm single-mode fibre. The resulting non-radiative energy transfer upconversion coefficients are at 500 wt ppm and at 1000 wt ppm. When the pump wavelength is set at 1017 nm, is very weak: less than . We measured that the population varies according to the pump power raised to the power 2.7. We conclude that the upconversion mechanism leading to the excitation of states in the PDFFA is different from all that which has been previously suggested and we propose a three-photon process. The application of our method requires the measurement of radiative emission branching ratios from levels and that we compare to the values calculated with the Judd - Ofelt analysis. We show that this analysis has to be used very cautiously with ions. Finally, we discuss the distribution of ions in ZBLAN glass. The fitting of fluorescence decay curves from level with the Inokuti-Hirayama model shows that the distribution of ions in ZBLAN is nearly homogeneous and no clustering effects are detected. Nevertheless, the non-exponential fluorescence decay curve of level even at very low concentrations is explained by the fact that the ions do not all have exactly the same environment in the glass.

Upconversion excitations in Pr3+-doped BaY2F8 crystal

“…This blue emission at about 490 nm can also be excited using the frequency conversion processes due to energy transfer (ET), excited state absorption (ESA) or photon avalanche (PA) [2,4,9]. Especially, upconversion processes in Pr 3+ doped low phonon crystals and ZBLAN glass fibers have been the subject of extensive studies [10,11].…”

Temperature dependence of the fluorescence lifetime in Pr3+:ZBLAN glass for fiber optic thermometry

“…The fluorescence decay curves thus obtained at a temperature of 320 K, with different doping levels of Pr 3ϩ in the glass, are shown in Fig. 3 The effect, however can be described in a satisfactory way by using the three-level model described, as discussed below. A comparison across these three different doping levels reveals that with increase of the concentration, the rate of crossrelaxation also increases, 9 which causes the decay of the 4000 ppm sample to be much faster than those of other two.…”

“…1 The development of, and subsequent research in, the erbium-doped silica fiber amplifier has been very successful, operating as it does at a wavelength of 1.55 m, which is around the optimum wavelength for low loss in optical communications. 3 The close proximity of the 1 G 4 level to the lower 3 F levels necessitates the use of fluoride glasses rather than oxide glasses as the material host, because of the lower phonon energies and the consequent expected reduction in nonradiative decay. 2 An alternative lies in using praseodymium, for which the 1 G 4 → 3 H 5 transition in Pr 3ϩ shows a broad emission band centered around 1.3 m and it should operate as a quasi-four-level system, making it one of the most promising routes for optical amplification on the 1.3 m wavelength band.…”

Influence of the oxygen-affected sites on decay times in Pr3+—activated fluoroaluminate glass

“…in Refs. [1,11]. In the absence of energy transfer the decays should be roughly singleexponential as the site-to-site disorder is not sufficiently great to cause substantial changes in the decay times.…”