Disordered laser gain media:: Er3+ doped CaGdAlO4 and Ca3Ga2Ge4O14

We report on the optical spectroscopy of trivalent erbium ions doped into compositionally disordered oxide host materials, CaGdAlO4 and Ca3Ga2Ge3O14. In either material, averaged spectral linewidths of close to 40 cm(-1) are measured to be concentration independent up to 5 mol% of the dopant ion. For laser excitation resonant with the I-4(15/2) --> F-4(9/2) and I-4(13/2) --> F-4(5/2) and F-4(3/2) transitions, intense blue and green upconversion fluorescence is observed. Dips in the upconversion excitation spectra are attributable to radiative energy transfer (or self-absorption) which is known to enhance energy storage and upconversion. (C) 2000 Elsevier Science B.V. All rights reserved.