Analysis of he laser performance of Tm3+，Tb3+(Ho3+):YVO4 crystals at～1.5μm wavelength

摘要

The absorption spectra of Tb,Tm:YVO4 and Ho,Tm:YVO4 are measured. The radiant and non-radiant transition probabilities from higher level to lower level, Ai,j and ?i,j, and the cross-relaxation probability are calculated in virtue of Judd-Ofelt and Dexter theories. The fluorescence lifetime of Tm3+ in the Tb3+ (or Ho3+) co-doped crystal is calculated. It indicates that the lifetime of initial level 3H4 of the laser transition can be shorter than that of terminal level 3F4 of the transition if the atomic percentage of Tb3+ (or Ho3+) ions is bigger than about 1 at%: namely, by means of the co-doping Tb3+ (or Ho3+) ions the self-termination phenomenon of laser light can be eliminated. Inserting the optic parameters to the formula deduced here on the laser threshold power Pth(4) and the slope efficiency ?s(4) of the four-energy-level system, we obtain the relationship of threshold power Pth(4) to the concentration of Tm3+ ions and discuss the effect of Tb3+ (or Ho3+) ion concentration on the laser threshold power Pth(4) around 1.5?m wavelength. The result shows that Tb,Tm:YVO4 crystal is a better choice to make the laser at ～1.5?m wavelength than Ho,Tm:YVO4crystal. We give the appropriate composition of (1-2) at% Tb, (1-2) at% Tm:YVO4, just for reference.