Optical characterization of glass materials doped with rare-earth elements

Abstract

ABSTRACT Suiphide glasses of GeGaS and GeGaAsS systems doped with rare earth ions are promising materials for various photonicapplications. Because the solubility of rare earth elements is influenced by the purity of host glass, namely by OH groupconcentration, the attention has been paid to the preparation of highly pure and homogeneous undoped and rare earthdoped glasses. Particularly the systems Ge0.25Ga0.1S0.65Pr and Geo.25Gao5Aso.o5So.65Pr with x500, 1000, 3000, 6000wt. ppm have been prepared. Synthesised material systems have been characterised by Raman and low-temperaturephotoluminescence spectroscopies. The optimal Pr concentration has been found to be around 1000 wt.ppm.. Theappearance oftemperature induced radiative transitions have been observed on GeGaS:Er samples.Key words: sulphide glasses, rare earth elements, photoluminescence, fibre lasers 1. INTRODUCTION There is a revival of interest in the rare-earth (RE) elements in the context of semiconductor and glass materials.Inspired by the spectacular results obtained on RE doped silica fibers which function as excellent fiber lasers and opticalamplifiers, there is a growing effort to prepare new glass materials doped with RE. This interest has been motivated by twocharacteristic properties of RE elements:a) sharp luminescence from screened inner shell (4f - 4ftransitions) practically independent ofthe host;b) strong tendency of RE to form oxides as well as compounds with elements of the 5th and the 6th rows of the atomicperiodic table.RE doped semiconductor compounds are attractive materials because they have the potential to combine the advantages ofoptical properties of RE ions and the electronic properties of semiconductor hosts. However, to introduce RE atoms intothe crystal lattice is difficult. On the other hand, RE doping of glass materials represents usually no problem.Luminescence from ions embedded into the glass host is broadened due to the inhomogeneous nature ofthe glass.Sharp luminescence from RE doped glass is thus observed only when RE forms cAystallites in the glass.Active, glass based, devices utilising the spectroscopic properties of rare earth (RE) cations are the subject of numerous