Thermal analysis and optical transition of Yb~(3+), Er~(3+) co-doped lead-germanium-tellurite glasses

摘要

In this article, we present a study of a new glass system: lead-germanium-tellurite glasses in the form of 0.05K_2O-0.1ZnO-0.1BaO-0.2PbO-xGeO_2-(0.55 -x)TeO_2 with x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.55. Differential temperature analysis of this glass system shows that increasing GeO_2 content raises the glass transition temperature (T_g) and suppresses the crystallization tendency in a large temperature range from T_g to the glass melting temperature. The maximum vibrational frequency is intermediate between germanate and fluoride glasses, in the range of 750 cm~(-1) to 820 cm~(-1). Subsequently, Optical absorption, photoluminescence, and upconversion fluorescence were measured for Yb~(3+), Er~(3+) co-doped lead-tellurium-germanate glasses. It was found that the full width at half-maximum of the fluorescence spectrum at 1534 nm decreases and the measured radiative lifetime increases with the replacement of TeO_2 by GeO_2. Excitation at 976 nm into the glass system leads to an intense green emission and a relatively weak red emission. With the addition of GeO_2, the increase of red fluorescence and the decrease of green emission in intensity are due to the increase of nonradiative transition rates between the ~4S_(3/2) and ~4F_(9/2) states of Er~(3+) ions. The quadratic dependence of the green and red emissions on excitation power indicates that two-photon absorption process occurs in this glass system excited at 976 nm.