Revealing the sequential nature of the Si-nanocluster-Er interaction by variable pulse duration excitation

The sequential nature of the Si-nanocluster-Er interaction is investigated by studying the time evolution of the Er luminescence intensity at 1.54 mu m, after exciting the system through high-power optical pulses with different time duration, in the range between 200 ns and 55 ms. It is shown that while Si nanocrystals and Er ions separately embedded in the SiO2 matrix can be approximated by an effective two level model, the Er-doped Si nanocluster system behaves differently under short pulse excitation. Indeed, for time durations shorter than the mean time between two successive excitations of a Si nanocluster, the number of excitable Er ions is shown to be limited by the total number of sensitizing centers and by the finite energy transfer time.