Judd-Ofelt modelling and stimulated-emission cross-sections for Tb3+ ions in monoclinic KYb(WO4)2 crystal

Absorption and emission properties of Er3+ ions in a cubic elpasolite crystal, Cs2NaYF6, are modeled within the Judd-Ofelt (J-O) theory. The J-O intensity parameters have been determined: ¿2 = 0.665, ¿4 = 0.217 and ¿6 = 0.029 ¿10-20 cm2. The elpasolite structure of Cs2NaYF6 containing isolated [YF6] polyhedra allows high Er3+ doping levels up to 100 at.% without considerable concentration quenching of luminescence and exceptionally long lifetimes of the excited states (in particular, the radiative lifetimes of the 4I13/2 and 4I11/2 states are as long as 36.7 ms and 113.4 ms, respectively). It also shows weak non-radiative relaxation. Stimulated-emission cross-sections have been determined for the Er3+ transitions in Cs2NaYF6 at ~2.7 and ~1.5 ¿m as well as in the visible spectral range