We have investigated the performance of blue upconversion fiber lasers based on thulium-doped ZBLAN fiber, operating at 480 nm with a 1140-nm pump. Extensive fluorescence measurements have provided the necessary spectroscopic data to present a computer model that describes the performance of such lasers with good accuracy despite the complicated three-step upconversion mechanism and the influence of ion–ion energy transfer processes. We have identified the mechanisms that populate the levels above the <sup>1</sup>G<sub>4</sub> level and are able to specify the corresponding spectroscopic parameters. We discuss the relevance of these processes to the 480-nm laser performance. Furthermore, we have calculated optimized parameters for such lasers.
© 1997 Optical Society of America
R. Paschotta, P. R. Barber, A. C. Tropper, and D. C. Hanna, "Characterization and modeling of thulium:ZBLAN blue upconversion fiber lasers," J. Opt. Soc. Am. B 14, 1213-1218 (1997)