Er~(3+) fluorescence in rare-earth aluminate glass

摘要

Er~(3+) ion fluorescence was excited with a 980-nm pump laser in Er-doped rare-earth aluminate (REAl) glasses with Er-dopant concentrations from 0.5-30 mol % (oxides basis). The spectral and decay characteristics were measured at ～1550 nm from Er~(3+) ~4I_(13/2) and at ～2750 nm from Er~(3+) ~4I_(11/2). Red and green light emissions were also observed, from Er~(3+) ~4F_(9/2) and ~4S_(3/2)+~2H_(11/2), respectively. The fluorescence decay rates are described by a model that yields an accurate fit of results at Er concentrations from 0.5 to 7 mol %. The radiative lifetime of Er~(3+) ~4I_(13/2) in Er:REAl glass is 6.12±0.26 ms. Hydroxyl ion quenching occurs at a rate given by 9.88 X 10~(-20) a_(OH)n_(Er) Hz, where a_(OH) is the glass absorption coefficient (in cm~(-1)) at a wavelength of 2950 nm and n_(Er) is the total Er ion concentration. The ~4I_(13/2) upconversion rate constant increases with the Er concentration to 1.35+0.05 X 10~(-18) cm~3/s at and above 7-mol % Er_2O_3. Er~(3+) ~4I_(11/2) fluorescence decays primarily by multiphonon quenching to ~4I_(13/2), at 7700±800 Hz, a rate that is slightly less than in tellurite glasses. The addition of 20-mol % silica to the glass has only a small influence on the fluorescence decay rates and greatly improves glass formation from the liquid to allow melting and casting of Er-doped REAl glass from platinum crucibles. The application of these Er-doped glasses in laser and optical device applications is briefly discussed.