White Upconversion in $Yb^{3+}//Tm^{3+}//Ho^{3+}$ Co-Doped Antimony-Germanate Glasses

In the paper the spectroscopic properties of antimony-germanate glass co-doped with $Yb^{3+}//Ho^{3+}$ has been investigated. Fabricated $Yb^{3+}//Tm^{3+}/Ho^{3+}$ co-doped glass is characterised by the emission of simultaneous multicolour upconversion luminescence. Strong blue $\text{}^{1}G_{4} \rightarrow \text{}^{3}H_{6}(Tm^{3+})$, green $\text{}^{5}F_{4} \rightarrow \text{}^{5}I_{8}(Ho^{3+})$ and red $\text{}^{5}F_{5} \rightarrow \text{}^{5}I_{8}(Ho^{3+})$ upconversion emission bands have been measured under 976 nm excitation at room temperature. Influence of molar ratio of active ions and excitation power on the colour coordinates (CIE-1931) have been investigated.