Abstract

On resonant excitation of the D levels of LaF₃:Nd with a tunable dye laser, fluorescence is observed from the R, S, A, D, E, K and L levels of which the last three levels are higher than the D levels. It has been reported by the authors¹ recently that both sequential two photon excitation process (STEP) and energy upconversion process (ETU) are responsible for the population drain mechanism from the lower D levels to the higher L level. In the present paper, the fluorescence from the R, S, and E levels and the processes through which they are populated will be discussed. Excitation spectra of the fluorescence from the R, S, and E levels have been recorded using the tunable laser excited by N₂ laser. The decay times for the D, R and S levels for three different concentrations 0.5, 2.0 and 5.0 percent by weight of Nd³⁺ have been determined. The decay times for R and S come out to be equal and they are 600, 400 and 150µs respectively for the three concentrations respectively. The fluorescence spectrum from the R level has been studied for concentrations of Nd³⁺ (0.1, 0.5, 2.0 and 5.0 percent by weight). The intensity increases as the concentration increases from 0.1 to 2.0 percent and then it decreases when the concentration becomes 5.0 percent. These studies indicate that the R level gets populated and depopulated through ion pair relaxations. The S levels are found to be populated due to thermal contribution from R levels. The two processes STEP and ETU are possibly responsible for the population of E level in the same manner as for the L level.

© 1984 Optical Society of America