Green up-conversion luminescence of erbium-doped oxyfluoride germanate fiber under continuous-wave laser-diode excitation

Up-conversion luminescence of Er3+-doped oxyfluoride germanate optical fiber is observed under laser-diode excitation. The enhanced green emission line is due to 2H11/2,4S3/2 → 4I15/2 transition of Er3+. The integrated luminescence intensity related to 2H11/2,4S3/2 → 4I15/2 (green) and 4F9/2 → 4I15/2 (red) transitions of Er3+ is reduced with increasing temperature. Several spectroscopic parameters of Er3+ ions in optical fibers were determined. The spectral linewidth is reduced, whereas the maximum of emission peak is shifted to longer wavelengths with increasing fiber length.