GeSx glass for Pr3+-doped fiber amplifiers at 1.3 μm

Germanium sulfide glass is investigated as host glass material for Pr3+-doped fiber amplifiers in the 1.3 μm telecommunications window. The solubility limit for Pr in GeSx glass is low. Only around 400 ppm Pr are soluble in GeS2 and 200 ppm in GeS2.5 and GeS3. At higher dopant levels, phase separation of a secondary crystalline (GeS2)3(Pr2S3)2 phase in the amorphous glass matrix produces a glass-ceramic material. The Pr3+ 1G4±3H5 photoluminescence spectrum of Pr-doped GeSx glass is located at 1.340 μm with a full-width at half-maximum of 0.11 μm. The emission lifetime of the Pr3+ 1G4 state at room temperature is 360 μs in (hydroxyl-free) GeSx glass. At a temperature of 10 K, the lower multiphonon relaxation rate of the non-radiative 1G4±3F4 transition increases the emission lifetime to 400 μs and it is shown that this lifetime can be considered to be the radiative lifetime of the Pr3+ 1G4 state in GeSx glass. The quantum efficiency is 0.9 in this glass at room temperature. Impurity hydroxyl, identified in some of the glasses by infrared spectroscopy, is shown to reduce the emission lifetime by non-radiative energy transfer from excited Pr to OH vibrations; OH is a serious Pr luminescence quencher in GeSx glass.