SPECTROSCOPIC PROPERTIES AND MECHANISMS OF EXCITED-STATE ABSORPTION AND ENERGY-TRANSFER UP-CONVERSION FOR ER3+-DOPED GLASSES

The upconversion fluorescences near 0.55 and 0.66 mum and Stokes fluorescences near 0.98 and 2.72 mum were measured for Er3+-doped aluminate, gallate and several other glasses under infrared excitation into the I-4(9/2) level. It was found that the quantum efficiencies of emissions from a given level, except the I-4(13/2) level, increased in the order of decreasing phonon energies of the glass hosts. The fluorescence originating from the I-4(13/2) level and its quantum efficiency are not dependent upon the phonon energies of glass hosts, due to influences of the energy transfer upconversion and excited state absorption from the I-4(13/2) level. Moreover this fluorescence is closely related to the I-4(11/2) lifetimes, in which the stronger fluorescence can be observed in a glass which has a shorter I-4(11/2) lifetime. The green upconversion fluorescence originating from the S-4(3/2) level mainly results from the excited state absorption from the I-4(13/12) level and the red upconversion fluorescence coming from the F-4(9/2) level mainly generates from the energy transfer upconversion through the I-4(13/2) level for Er3+-doped aluminate and gallate glasses.