Spectral properties of erbium-doped HMO glasses for 1.5 μm broadband amplification

The heavy metal oxide (HMO) glasses in the ternary Bi₂O₃-WO₃-TeO₂ system were prepared to investigate the Er³⁺ amplification properties. The present HMO glasses showed larger and broader Er³⁺ emission spectra as compared with the conventional silica-based glasses. Dominant factors on the emission intensity and bandwidth were explored on the basis of theories. The emission intensity was successfully explained by the theoretical radiative decay rate, and it was also confirmed that the refractive index was predominant on the emission intensity. A Judd-Ofelt Ω₆ parameter was also examined, and its influence on the bandwidth was not recognized. Other factors, such as O1s binding energy and structural variation around Er³⁺ ions, were estimated, and their effects on the bandwidth were however not clarified. The unique chemical bonding character in the HMO glasses might be responsible for the spectral broadening.