Rise kinetics of up-conversion luminescence of the LiY$_{0.8}$Yb$_{0.2}$F$_{4}$ : Tm$^{3+}$ (0.2 at.%) crystal with pulsed excitation

The regression analysis of the rise kinetics of up-conversion luminescence of the LiY$_{0.8}$Yb$_{0.2}$F$_{4}$ : Tm$^{3+}$ (0.2 at.%) crystal is performed. The kinetics curve is obtained with rectangular pulsed excitation by radiation from a laser diode (IR LD) with a wavelength of $\lambda_ p$ = 933 nm. The most important—in these experimental conditions—mechanisms of the energy transfer from Yb$^{3+}$ ions to Tm$^{3+}$ ions are established, which are responsible for the transitions between the ground $^{3}$H$_{6}$ and excited $^{3}$F$_{4}$, $^{3}$H$_{4}$,$^{1}$G$_{4}$, $^{1}$D$_{2}$, and $^{1}$I$_{6}$ terms of the Tm$^{3+}$ ions. The durations of the relevant energy transfer processes are determined. It is shown that the energy transfer between rare earth ions in the LiY$_{0.8}$Yb$_{0.2}$F$_{4}$ : Tm$^{3+}$ (0.2 at.%) crystal occurs through the dipole–dipole interactions.