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

We present an investigation of Er3+ photoluminescence in Y2O3 waveguides co doped with Eu3+. As a function of europium concentration we observe an incr ease in decay rate of the erbium I-4(11/2) energy level and an increase of the ratio of photoluminescence emission from the I-4(13/2) and I-4(11/2) st ates. Using a rate equation model, we show that this is due to an energy tr ansfer from the I-4(11/2)-->I-4(13/2) transition in erbium to europium. Thi s increases the branching ratio of the I-4(11/2) state towards the I-4(13/2 ) state and results in a higher steady state population of the first excite d state of erbium. Absolute intensity enhancement of the I-4(13/2) emission is obtained for europium concentrations between 0.1 and 0.3 at. %. In addi tion, the photoluminescence due to upconversion processes originating from the I-4(11/2) state is reduced. Using such state-selective energy transfer the efficiency of erbium doped waveguide amplifiers can be increased. (C) 2 000 American Institute of Physics. [S0021-8979(00)01321-9].