Efficient sensitisation of praesodymium 1.31 μm fluorescence by optically pumped ytterbium ions in ZBLAN glass

The authors report efficient population of the ¹G₄ level of trivalent praseodymium by radiationless energy transfer from trivalent ytterbium ions optically pumped at 980 nm. Subsequent fluorescence at 1.31 μm is optimised in a ZBLAN host for concentrations of 0.3 wt% Pr³⁺ and 2 wt% Yb³⁺. The quantum efficiency for conversion of an excited Yb³⁺ ion to an excited Pr³⁺ ion at these dopant concentrations is determined to be 56%