Abstract

Recent developments of 2 µm lasers with Tm, Ho and Tm/Ho doped materials indicate that at high inversion levels loss due to upconversion of excited ions in the upper laser level becomes significant. Although some attempts have been made to characterize these loss mechanisms¹·², indirect pumping of the upper laser level was used in these studies. To measure the upconversion rate it requires a detailed knowledge of the excited state densities. In this study, the Ho ions are selectively excited to ⁵I₇ to create a uniform distribution of excited ions and emissions from higher excited states are monitored as a measure of the upconversion processes.

© 1992 Optical Society of America