Highly Er^3 ＋／Yb^3＋ Co-Doped Fluoroaluminate Glasses for Microchip Laser at 1.54μm

A series of highly Er^3 /Yb^3 co-doped fluoroaluminate glasses were investigated in order to develop a microchip laser at 1.54μm under 980nm excitation. Measurements of absorption, emission and up-conversion spectra were performed to examine the effect of concentration quenching on spectroscopic properties. In the glasses with Er^3 concentrations below 10% (mol fraction), concentration quenching is low and the Er^3 /Yb^3 co-doped fluoroaluminate glasses gave stronger fluorescence of 1.54μm from the 4113/2→^4I15/2 transition than those of Er^3 singly-doped glasses. In the glass with Er^3 concentrations above 10%, concentration quenching of 1.54μm obviously occurs more than that of the Er^3 singly-doped samples because of the back energy-transfer from Er^3 to Yb^3 . To obtain the highest emission efficien-cy at 1.54μm, the optimum doping-concentration ratio of Er^3 /Yb^3 is found to be approximately 1 : 1 in mol fraction when the Er^3 concentration is less than 10%.