Analysis of cross relaxation between Tm3+ ions in PbO−Bi2O3−Ga2O3−GeO2 glass

Abstract

Mechanisms of cross relaxation (3H4, 3H6→3F4, 3F4) in Tm3+ -doped PbO−Bi2O3−Ga2O3−GeO2 glass were analyzed. The energy gap between the absorption (3H6→3F4) and emission (3H4→3F4) spectra was approximately 600 cm−1. A large decrease in cross relaxation rates at low temperatures indicated that cross relaxation is controlled by a phonon-assisted energy transfer. The bending vibration of the Ga–O–Ga bonds between GaO4 tetrahedra (∼550 cm−1) was directly responsible for this energy transfer. Although GeO2 was added to enhance the thermal stability of PbO−Bi2O3−Ga2O3 glass, the phonon mode associated with vibration of GeO2 (∼770 cm−1) was not involved in the cross relaxation process.