Upconversion in LaF3:Tm3+

Abstract

When excited by the 6471-Å line from a krypton laser, blue and uv fluorescence has been observed in La${\mathrm{F}}_3$: ${\mathrm{Tm}}^{3+}$ at room temperature. The main emission features have been identified as originating from the ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$ and ${}_{}{}^1{}_{}{}^{}G_4^{}{}_{}{}^{}$ levels, reached by a stepwise excitation process. A set of accurate Judd-Ofelt $\Omega$ parameters for La${\mathrm{F}}_3$: ${\mathrm{Tm}}^{3+}$ has been derived from the measured lifetime of the ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$, ${}_{}{}^1{}_{}{}^{}G_4^{}{}_{}{}^{}$, ${}_{}{}^3{}_{}{}^{}H_4^{}{}_{}{}^{}$, and ${}_{}{}^3{}_{}{}^{}F_4^{}{}_{}{}^{}$ levels.