Emission properties of TM3+-Ln3+ (Ho3+, Tb3+, Eu3+) co-doped tellurite glasses by energy transfer

Generally, it is difficult for 1.4 mum band amplification to form population inversion between the initial H-3(4) and the terminal F-3(4) levels in Tm3+, because lifetime of the initial level is shorter than that of the terminal level. Accordingly emission properties and lifetimes of tellurite glasses co-doped with Tm3+ and various rare earth ions (Ho3+, Tb3+ and Eu3+) were investigated in order to improve the population inversion by co-doping method. These co-doped ions depopulated the terminal level rapidly by energy transfer from the terminal level to the co-doped ion. Especially, for the initial level, Ho3+ did not affect the population of the initial level because Ho3+ cannot easily cause cross-relaxation. Ho3+ had the largest effect on lifetime of the terminal level without decreasing the population of the initial level. Ho3+ showed the best performance among three investigated rare earth ions as a co-doped ion.