Erbium-Doped Fluoroborate Glasses for Near Infrared Broadband Amplifiers

Erbium (Er3+)-doped alkali lead tellurofluoroborate (RLTB) glasses were prepared and characterized systematically through optical absorption and emission measurements. The emission spectra in the range 450-900 and 1400-1800 nm were recorded by exciting the samples with 532 nm (Nd : YVO4 crystal) and 514.5 nm (Ar+ laser), respectively. Applying Judd-Ofelt analysis, the intensity parameters have been determined using experimental oscillator strengths of absorption bands. From the Judd-Ofelt intensity parameters, some important fluorescence properties such as spontaneous transition probabilities, radiative lifetimes and luminescence branching ratios for the S-4(3/2) -> I-4(15/2) (0.55 mu m), S-4(3/2) -> I-4(13/2) (0.85 mu m), and I-4(13/2) -> I-4(15/2) (1.54 mu m) emission transitions of Er3+ ion in RLTB glasses have been calculated. The continuous pumping of the samples results in fast nonradiative decay through H-2(11/2) -> F-4(9/2) (similar to 3500 cm(-1)) transition, which in turn causes the population of Er3+ ions from H-2(11/2) state to the higher F-4(3/2) state. The emission cross sections determined for the I-4(13/2) -> I-4(15/2) (1.54 mu m) transition using the McCumber theory are in good agreement with the values obtained from the Judd-Ofelt analysis. From evaluated radiative parameters, it is suggested that these RLTB glasses are more suitable candidates for 0.85 and 1.54 mu m broadband optical amplifiers.