Concentration dependence of upconversion emission from Er:YAG fibers

Fibers of Er:YAG have been grown using the laser-heated pedestal growth method. Fibers with Er concentrations ranging from 0.5 to 10 mol. % have been produced and excitation at 965 nm has been used to produce intense upconversion emission at green and red wavelengths. The dependence of ground state absorption and upconversion emission on dopant concentration has been studied and shown to exhibit lower levels of self-absorption than previously reported. At Er concentrations of 5 mol. % and above; however, the variation of upconversion emission intensity with pump power deviates from theoretical predictions, exhibiting saturation behavior consistent with concentration quenching.