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

In rare earth doped chalcogenide glasses, hydrocarbon and hydroxyl based impurities affect the absorption and fluorescence properties. Corresponding to Fourier transform infrared spectroscopy (FTIR) investigations sulfur is the 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 arsenic sulfide (900°C, evacuated sealed quartz glass ampoules) hydrocarbon species tend to react with oxide impurities (As2O3, GeO2) and hydroxyl with carbon oxysulfide and carbon dioxide. Excess of carbon appears as carbon disulfide (CS2) in the FTIR spectra. The specific absorption coefficient of CS2 is found to be 0.012±0.003cm−1/wt.ppm. Hydrocarbon impurities additionally increase the hydrosulfide content of samples. Based on the FTIR investigationes the specific absorption coefficient of the alkane C24H50 is estimated to be 0.006±0.001cm−1/wt.ppm. The `oxygen trap process' of carbon and hydrocarbon components in chalcogenide glasses is confirmed by thermodynamic calculations. The defined adjustment of hydrosulfide (500–1000 wt.ppm) and hydroxyl content (less 3 wt.ppm) of the As–Ge–Ga–S glass by carbon/hydrocarbon doping allowed us to prepare optimised fibers with attenuation 1.5–2 dBm−1 and a sufficient lifetime of the excited level 1G4 220–180 μs at 750 wt.ppm Pr3+. The glass is introduced as core material in a single mode fiber for 1.3 μm amplification.