Experimental determination of the upconversion rate in erbium-doped silicate glasses

A new experimental method for direct determination of the upconversion coefficient C(up) in Er-doped glasses is presented. This method is based on measurement of the dependence on pump power of the fluorescence quantum yield at 1.54 microm and of the excited-state absorption. Two methods are used for determination of the population of the excited Er ions. The first is based on the measurement of the variation in stimulated emission and on the variation in ground-state absorption for the (4)I(15/2)<-->(4)I(13/2) transition range. In the second, the excited-state absorption is measured for the (4)I(13/2) -->(4)F(7/2) transition. This method is successfully applied to Er-doped silicate glass fibers. The value of C(up) experimentally obtained is in good agreement with previously published results.