Cooperative Upconversion, Radiation Trapping, and Self-Quenching Effects in Highly Yb3+-Doped Oxyfluoride Glasses

In this work we report the successful preparation of fluorophosphate glasses in the new compositional line 20Al(PO3)(3)-10AlF(3)-25BaF(2)-25SrF(2)-(20-x)YF3-xYbF(3) with x varying from 0 to 20 mol%, and their detailed spectroscopic investigation with respect to (non-) radiative decay processes. More precisely, we focus on the study of three important effects in Yb3+ doped systems, namely radiation trapping (RT), self quenching (SQ), and cooperative luminescence (CL). The characteristic improvement in hydrolytic stability and phonon energy of the glasses, as compared to phosphates, for example, result in long F-2(512) radiative lifetime value (tau(o) = 1.2 ms) and high critical Yb3+ concentration (Q = 6.8 x 10(20) ions/cm(3)). A very strong radiation trapping effect was observed in the investigated samples which can be favorably used to generate highly efficient energy upconversion in the blue, through Yb-Yb cooperative effect. The CL was investigated and quantified yielding, to the best of our knowledge, the highest CL parameter [k = (5.85 +/- 0.08) x 10(-18) cm(3)/s], which is associated to a CL rate of 32 s(-1) for a typical pump power of similar to 100 mW. These characteristics evidence the potential applications of the present Yb3+-doped oxyfluoride glasses for blue emitting devices, as well as for infrared ones.