Er 3 + fluorescence in rare-earth aluminate glass

Abstract

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 0.5–30mol% (oxides basis). The spectral and decay characteristics were measured at ∼1550nm from Er3+I13∕24 and at ∼2750nm from Er3+I11∕24. Red and green light emissions were also observed, from Er3+F9∕24 and S3∕24+H11∕22, respectively. The fluorescence decay rates are described by a model that yields an accurate fit of results at Er concentrations from 0.5to7mol%. The radiative lifetime of Er3+I13∕24 in Er:REAl glass is 6.12±0.26ms. Hydroxyl ion quenching occurs at a rate given by 9.88×10−20 aOHnEr Hz, where aOH is the glass absorption coefficient (in cm−1) at a wavelength of 2950nm and nEr is the total Er ion concentration. The I13∕24 upconversion rate constant increases with the Er concentration to 1.35+0.05×10−18cm3∕s at and above 7-mol% Er2O3. Er3+I11∕24 fluorescence decays primarily by multiphonon quenching to I13∕24, at 7700±800Hz, 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.