Characterization and modeling of thulium:ZBLAN blue upconversion fiber lasers

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 (1)G(4) 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. (C) 1997 Optical Society of America.