Dynamics of upconversion photoluminescence in Ge-Ga-S: Er3+: application of quadrature frequency resolved spectroscopy

摘要

Quadrature frequency resolved spectroscopy (QFRS) on green (similar to 550nm) upconversion photoluminescence (UCPL) of Ge-Ga-S: Er3+ glasses pumped at 975nm revealed double-peaked spectra with long lifetime (1) ranging from 0.2 to 2ms and short lifetime (2) approximate to several tens of s. The results are analysed in terms of the transfer function derived by linearizing rate equations for a three-level model. The (1) component is attributed to the relaxation at the intermediate level I-4(11/2) of Er3+ ions and the (2) component, to that at the upper S-4(3/2) manifold. The dominance of energy transfer upconversion over excited state absorption in the UCPL manifest itself as a greater dependence of (1) on the pump power and a lower ratio of the components of (2) to (1) in the QFRS spectra of a heavily Er-doped sample.