Effects of carbon, hydrocarbon and hydroxide impurities on praseodymium doped arsenic sulfide based glasses

In rare earth doped chalcogenide glasses, hydrocarbon and hydroxyl based im purities affect the absorption and fluorescence properties. Corresponding t o Fourier transform infrared spectroscopy (FTIR) investigations sulfur is t he main source of these impurities. The simultaneous occurrence of H, O, C impurities leads to an interaction influenced by the preparation conditions . Under melting conditions of arsenic sulfide and germanium/gallium doped a rsenic sulfide (900 degreesC, evacuated sealed quartz glass ampoules) hydro carbon species tend to react with oxide impurities (As2O3, GeO2) and hydrox yl with carbon oxysulfide and carbon dioxide. Excess of carbon appears as c arbon disulfide (CS2) in the FTIR spectra. The specific absorption coeffici ent of CS2 is found to be 0.012 +/- 0.003 cm(-1)/wt.ppm. Hydrocarbon impuri ties additionally increase the hydrosulfide content of samples. Based on th e FTIR investigationes the specific absorption coefficient of the alkane C2 4H50 is estimated to be 0.006 +/- 0.001 cm(-1)/wt.ppm. The 'oxygen trap pro cess' of carbon and hydrocarbon components in chalcogenide glasses is confi rmed by thermodynamic calculations. The defined adjustment of hydrosulfide (500-1000 wt.ppm) and hydroxyl content (less 3 wt.ppm) of the As-GeGa-S gla ss by carbon/hydrocarbon doping allowed us to prepare optimised fibers with attenuation 1.5-2 dB m(-1) and a sufficient lifetime of the excited level (1)G(4) 220-180 mus at 750 wt.ppm Pr3+. The glass is introduced as core mat erial in a single mode fiber for 1.3 mum amplification. (C) 2001 Elsevier S cience B.V. All rights reserved.