Laser-diode-excited Blue Upconversion in Tm3+/Yb3+-codoped TeO2-Ga2O3-R2O (R=Li, Na, K) Glasses

摘要

This paper reports on intense blue upconversion in Tm3+/Yb3+ codoped TeO2-Ga2O3-R2O(R=Li, Na, K) glasses upon excitation with commercial available laser diode (LD). Effects of alkali ions on the Raman spectra, thermal stability and spectroscopic properties of the tellurite-gallium glasses have also been investigated. Energy transfer and the involved upconversion mechanisms have been discussed. Intense blue upconversion emission centered at 476 nm along with a weak red emission at 650 nm has been observed upon excitation of 977 nm LD, assigned to the transitions of ${}^{1}G_{4} to {}^{3}{text{H}}_{{text{6}}} $ , and ${}^{1}G_{4} to {}^{3}{text{H}}_{{text{4}}} $ and/or ${}^{3}{text{F}}_{{2,3}} to {}^{3}{text{H}}_{{text{6}}} $ of Tm3+, respectively. The blue upconversion intensity has a cubelike dependence on incident pump laser power, indicating a three-photon process. However, a quadratic dependence of the 476 nm upconversion intensity on the incident pump laser power has been observed when samples under excitation of 808 nm LD due to a two-photon absorption process. Enhanced upconversion luminescence have been observed with replacing K+ for Na+ and Li+.