OPTICAL AND SPECTROSCOPIC CHARACTERIZATION OF ND-DOPED ALUMINOSILICATE FIBER PREFORMS MADE BY THE MCVD METHOD USING CHELATE DELIVERY

Time-resolved fluorescence decay measurements from the F-4(3/2) level of Nd3+ in aluminosilicate optical fiber preforms after 807-nm excitat ion are reported in the temperature range from 15 degrees C to 500 deg rees C for Nd2O3 concentrations in the range from 0.2 to 0.9 wt % and Al2O3 concentrations of between 3.8 wt % and 8 wt %. At room temperatu re it is observed that for concentrations of less than 0.6 wt % Nd2O3 the fluorescence decay is approximately exponential; for the higher Nd 2O3 concentrations the decay is increasingly bi-exponential. We have i dentified a ''slow'' (approximate to 500 mu s) and a ''fast'' (approxi mate to 100 mu s) decay time; the slow decay is attributed to isolated ions and the faster decay to energy transfer between homogeneously di spersed ions. The measured 1/e folding fluorescence decay time tau dec reases slowly at a constant rate of - 0.08 +/- 0.007 mu s/K for 0.9 wt % Nd2O3 It is shown that increasing the Al2O3 concentration tends to suppress this temperature quenching effect. A radiative decay time of 640 mu s is obtained by Judd-Ofelt analysis.