Short wavelength up-converted emission studies in Er3+ and Yb3+ doped ZBLAN glasses

In this work we present the results of our recent studies on up-conversion phenomena in erbium and ytterbium doubly doped ZBLAN glasses. The unique excitation sources - pressure-tuned semiconductor laser diodes, enabling wavelength tuning over a broad spectral range - have been deployed for the first time to investigate up-conversion efficiency and optimize the wavelength of excitation of ZBLAN glasses singly doped with Er3+ and doubly doped with Er3+ and Yb3+. The set of samples differing in activator and sensitizer concentrations was exposed to careful investigation by means of optical spectroscopy, with specific attention focused on the efficiency of up-conversion processes resulting in short-wavelength emission from 4S3/2 + 2H11/2 energy levels. The concentration-dependent luminescence characteristics were measured for all disposed samples under direct and up-converted excitation. These were complemented by analysis of the visible luminescence decay profiles obtained under direct excitation and power dependencies as well. The obtained results enabled modeling of mechanisms, analysis of the nature of processes observed in both types of active media and comparison of up-conversion efficiency.