Low-temperature photoluminescence in chalcogenide glasses doped with rare-earth ions

Sulfide and oxysulfide bulk glasses Ga-La-S-O, Ge-Ga-S and Ge-Ga-As-S doped, or co-doped, with various rare-earth (RE3+) ions are investigated for their room temperature transmission and low-temperature photoluminescence. Photoluminescence spectra are collected by using external excitation into the Urbach tail of the fundamental absorption edge of the host-glass. The low-temperature photoluminescence spectra are dominated by the broad-band luminescence of the host glass, with superimposed relatively sharp emission bands due to radiative transitions within 4f shells of RE3+ ions. In addition, the dips in the host-glass luminescence due to 4f-4f up-transitions of RE3+ ions are observed in the Ge-Ga-S and Ge-Ga-As-S systems. These superimposed narrow effects provide a direct experimental evidence of energy transfer between the host glass and respective RE3+ dopants.