Abstract

Bulk hosts codoped with Er³⁺/Yb³⁺ ions are an important class of laser materials for eyesafe applications in the 1.5-1.7μm spectral region. These quasi-3-level systems rely on the efficient absorption of 900-1000nm pump radiation by Yb³⁺ sensitizer ions and subsequent resonant energy transfer to the ⁴I_11/2 Er³⁺ state and finally to the metastable ⁴I_13/2 upper laser level of the Er³⁺ activator. Due to the complex energy-level structure of Er³⁺, the full laser cycle of such systems is susceptible to loss mechanisms like bottlenecks, leaks to interfering states and thermal occupation of the terminal laser levels. A multitude of time constants are linked to the transition steps involved in the complete laser cycle. In association with pump-pulse characteristics, these phenomena may both affect laser efficiency and give rise to interesting output pulse-timing effects.

© 2007 IEEE