Abstract

The spectroscopic properties of Er³⁺ -doped and Yb³⁺, Er³⁺-codoped sodium- and alumino-silicate glasses, potential planar optical waveguide amplifier materials for 1.55 μm, are investigated. With the exception of ⁴I_13/2, multiphonon relaxation is dominant for all Er³⁺ excited-state multiplets, allowing efficient population of the emitting ⁴I_13/2 state by ⁴I_11/2 excitation around 980 nm. In both glasses, multiphonon relaxation from ⁴I_13/2 is negligible up to 678 K, and the respective 300 K absolute quantum yields are ~0.9 for 0.05 mol% Er³⁺-doped samples under low-power ⁴I_11/2 excitation. OH⁻ impurities are able to efficiently quench ⁴I_13/2 excitation. Absolute ⁴I_13/2 (Er³⁺) and ²F_5/2 (Yb³⁺) quantum yields are used to predict an optimum Yb³⁺, Er³⁺ concentration range for sensitization. Yb³⁺ codotation strongly enhances pump-light absorption and increases ⁴I_13/2 population by almost two orders of magnitude in some samples. Relative ²H_11/2/⁴S_3/2 upconversion luminescence intensities are shown to be a sensitive measure for the substantial internal sample heating observed in Yb³⁺ codoped glasses.

© 1996 Optical Society of America