Cooperative upconversion effects on the performance of Er^3+-doped phosphate glass waveguide amplifiers

Abstract

The cooperative upconversion processes of erbium ions in silver film ion-exchanged waveguides in a phosphate glass were studied from the pump intensity dependence of luminescence decay curves. Cooperative upconversion coefficients of the 4I13/2 level, 7.7±0.7×10-19 and 9.3±0.7×10-19 cm3/s, were obtained for an Er3+ concentration of 1×1020 cm-3 in bulk and waveguide samples, respectively. These values are 1 order of magnitude smaller than the ones reported for silica glass. The increase in the cooperative upconversion coefficient with the increase in Er3+ concentration was found to be small. The effects of cooperative upconversion on the gain performance were analyzed for different Er3+ concentrations by a theoretical model based on experimentally measured gain with a 1.48-µm pump wavelength. Given the small cooperative upconversion coefficients in this glass, Er3+ concentrations potentially as high as 3.7×1020 cm-3 were shown to be feasible. Such high concentrations would result in a 12-dB gain at 150-mW pump power with a 4-cm-long waveguide.