Abstract

Efficient infrared (1480mn) to visible (407nm, 540mn and 670nm) frequency upconversion has been studied in a new host material doped with erbium very promising for photonics applications. The fluoroindate host glass employed is transparent from the UV (200nm) to the middle-inlrared 8µm), resistant to atmospheric moisture and capable of incorporating large concentrations of RE ions to the matrix|1|. In this work, un efficient CW pumped upconversion scheme has been realized. The glass sample used had the following composition in mol %: 39-x InF3 - 20 ZnF₂ - 16 BaF₂ - 20 SrF₂ - 2GdF3 - 2NaF - 1 GaF₃ – xErF₃ (x = 1,2,3). The glass was obtained by fluoration of In₂O₃ at 400°C with NH₄F and HF in a platinum crucible. Then, all fluoride components were mixed and heated in a dry box under argon atmosphere at 700°C for melting and 800° C for finning. After this process, the melt was poured and cooled into a pre-heated brass mold. The samples obtained have good optical quality and volumes of a few cubic centimeters. Optical absorption was readily obtained with a conventional spectrophotometer and the upconversion processes were studied pumping with a cw semiconductor laser diode with maximum intensities of 200W/cm², corresponding to 5.6mW average power. The observed emissions corresponding to radiative transitions of the 4l⁺¹ electrons in the Er³⁺- ions from excited slates to the ground state are identified in fig. 1, where the excitation pathway is also indicated. The lines at ~540nm and ~670nm are readily visible by the naked eye and all spectroscopic measurements were taken at room temperature. The recorded spectra were analized with respect to their pump power dependence and temporal behavior The results showed that different number of photons were involved in the mechanisms leading to the unconverted emissions.

© 1996 IEEE