Optical properties of Tm-Er codoped aluminate glasses

Transparent CaO-Al₂O₃-B₂O₃ glasses codoped with Tm³⁺ and Er³⁺ were prepared by melt quenching and subsequent heating. Optical absorption spectra revealed an ultraviolet to visible absorption band corresponding to a relative electronic transition of Tm³⁺ and Er³⁺. For Tm-only doped glasses, the 791-nm absorption line is prominent and also has comparable strength in Tm-Er codoped glasses. Both 405-nm and 791-nm wavelengths have been used as excitation sources to comparatively study the photoluminescence characteristics of Tm³⁺ and Er³⁺. Only Er³⁺ emission at 1528 nm has been observed under a pumping wavelength of 405 nm. However, both Tm ³⁺ and Er³⁺ emission can be found with an excitation wavelength of 791 nm. It implies that 791 nm should be very effective for pumping Tm-Er codoped aluminate glass for application in broadband optical waveguide amplifiers.