Correlation of the Orbach Relaxation Coefficient with Optical Linewidths: LaF3:Er3+

Abstract

We have measured the lifetime of the first excited state of trivalent erbium in lanthanum fluoride, and find, for 0.05% erbium concentration, an inverse lifetime $W=(7.0\mathrm{}\pm 0.9)\times {10}^{10}$ ${\sec }^{-1\mathrm{}}$. For this salt, this value is observed to be equal to the Orbach coefficient occurring in the spin-lattice relaxation of the ground-state doublet, recently measured by M. Schulz using electron-spin-resonance techniques. The equality of the inverse lifetime and the Orbach coefficient is in agreement with existing theory. We have also observed concentration-dependent satellite structure in the ground state of trivalent erbium in lanthanum fluoride, which we tentatively attribute to exchange-coupled pairs. We have also observed concentration-dependent broadening in the optical transitions studied; this may be evidence of energy transfer between impurity ions.