Laser-induced fluorescence line narrowing in Sm2+-doped fluoride glass.

Abstract

Fluorescence line-narrowing experiments have been made for the ${\mathrm{Sm}}^{2+}$ ion in fluoride glass at 77 K under cw dye-laser excitation at various energies within the inhomogeneously broadened $^{7}$${\mathit{F}}_{0\mathrm{\ensuremath{-}}}^{5}$${\mathit{D}}_{0}$ and $^{7}$${\mathit{F}}_{0\mathrm{\ensuremath{-}}}^{5}$${\mathit{D}}_{1}$ absorption lines. The energies of the three Stark levels of the $^{7}$${\mathit{F}}_{1}$ and $^{5}$${\mathit{D}}_{1}$ manifolds have been obtained as a function of the $^{5}$${\mathit{D}}_{0\mathrm{\ensuremath{-}}}^{7}$${\mathit{F}}_{0}$ energy separation. From the analysis of this result, it has been found that the site-to-site variations of the energies of these Stark levels can be explained well only by taking into account the J-mixing effect. The low-energy levels of the 4${\mathit{f}}^{5}$5d configuration lie in the vicinity of the $^{5}$${\mathit{D}}_{\mathit{J}}$ states in this material. However, no effect of the crystal-field mixing of the 4${\mathit{f}}^{5}$5d states on the inhomogeneous distribution of the energies of the $^{7}$${\mathit{F}}_{1}$ and $^{5}$${\mathit{D}}_{1}$ states has been observed. The origin of the unusually intense $^{5}$${\mathit{D}}_{0\mathrm{\ensuremath{-}}}^{7}$${\mathit{F}}_{0}$ transition in ${\mathrm{Sm}}^{2+}$ is also discussed.