Sensitization of Er luminescence by Si nanoclusters

Sensitization of Er emission by Si nanoclusters (Si-nc) is investigated with pulsed and continuous optical pumping, in and off resonance with excited states of Er³⁺ ion. We show that under high-power pulsed pumping, the excitation process is limited by the finite energy transfer time from Si-nc to Er³⁺ ions. By comparison between pulsed and steady-state excitation, the concentration of sensitizers and average number of Er³⁺ ions coupled to a single nanocluster are independently determined in an experiment. The results clarify conditions needed for efficient sensitization of SiO₂:Er by Si-nc.