Fluoride-assisted hydroxyl reduction in Er3+-doped tellurite glass and amorphous thin films for enhanced optical and spectroscopic performances

Abstract

Tellurite glass with the composition 68.25 TeO₂–19.5 ZnO–9.75 Bi₂O₃–2.5 Er₂O₃ (in mol%) is a promising material for integrated photonics. However, the emission efficiency of erbium ions in the glass host is constrained by the strong absorption of hydroxyl groups present in the glass. To counteract these losses arising from hydroxyl groups, ammonium bifluoride as a dehydrating agent is added to the glass batch before melting and its impact not only on the optical, thermal, structural, and spectroscopic properties of the glass but also on the properties of amorphous thin films is examined. A reduction in hydroxyl group concentration is confirmed in the bulk, leading to an enhancement in the glass spectroscopic properties. However, residual fluorine originating from the ammonium bifluoride remains in the glass. While the presence of fluorine in the glass target has minimal impact on the deposition process itself, fluorine is also found in the film, resulting in a film with a lower refractive index than initially targeted. Nevertheless, the films deposited from the dehydrated glass target are seen to exhibit similar properties close to those of films from a non-dehydrated target.