Kinetics of pair-induced quenching in holmium-doped optical fibers

We present a study of the dynamics of the rapid energy transfer upconversion that occurs within pairs or clusters of holmium ions, commonly referred to as pair-induced quenching. The lifetime of excited holmium ion pairs is determined to be around 0.4 µs from time-resolved fluorescence measurements. We develop a rate equation model that incorporates this lifetime and evaluate numerically and experimentally the consequences this finite intra-cluster upconversion rate has on the performance of a nanosecond-pulsed Ho-doped fiber amplifier. We demonstrate a significant improvement in efficiency by utilizing pulsed pumping on a timescale shorter than the measured excited ion pair lifetime.