Selective modification of the Er3+ 4I11/2 branching ratio by energy transfer to Eu3+

Abstract

We present an investigation of ${\mathrm{Er}}^{\mathrm{3+}}$ photoluminescence in ${\mathrm{Y}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}$ waveguides codoped with ${\mathrm{Eu}}^{\mathrm{3+}}.$ As a function of europium concentration we observe an increase in decay rate of the erbium ${}^4{I}_{\text{11/2}}$ energy level and an increase of the ratio of photoluminescence emission from the ${}^4{I}_{\text{13/2}}$ and ${}^4{I}_{\text{11/2}}$ states. Using a rate equation model, we show that this is due to an energy transfer from the ${}^4{I}_{\text{11/2}}{\to }^4{I}_{\text{13/2}}$ transition in erbium to europium. This increases the branching ratio of the ${}^4{I}_{\text{11/2}}$ state towards the ${}^4{I}_{\text{13/2}}$ state and results in a higher steady state population of the first excited state of erbium. Absolute intensity enhancement of the ${}^4{I}_{\text{13/2}}$ emission is obtained for europium concentrations between 0.1 and 0.3 at. %. In addition, the photoluminescence due to upconversion processes originating from the ${}^4{I}_{\text{11/2}}$ state is reduced. Using such state-selective energy transfer the efficiency of erbium doped waveguide amplifiers can be increased.