SPECTROSCOPIC PROPERTIES AND UP-CONVERSION MECHANISMS IN ER3-DOPED FLUOROINDATE GLASSES()

Fluorindate glasses containing 1,2,3,4 ErF3 mol % were prepared in a d ry box under argon atmosphere. Absorption, Stokes luminescence (under visible and infrared excitation), the dependence of S-4(3/2) I-4(11/2) , and I-4(13/2) lifetimes with Er concentration, and upconversion unde r Ti-saphire laser excitation at lambda=790 nm were measured, mostly a t T=77 and 300 K. The upconversion results in a strong green emission and weaker blue and red emissions whose intensity obeys a power-law be havior I similar to P-n, where P is the infrared excitation power and n = 1.6, 2.1, and 2.9 for the red, green, and blue emissions, respecti vely. The red emission exponent n = 1.5 can be explained by a cross re laxation process. The green and blue emissions are due to excited stat e absorption (ESA) and energy transfer (ET) processes that predict a f actor n=2 and n=3 for the green and blue emissions, respectively. From transient measurements we concluded that for lightly doped samples th e green upconverted emission is originated due to both processes ESA a nd ET. However, for heavily doped samples ET is the dominant process.