Multicolor up conversion emission and color tunability in Yb/Tm/Ho triply doped heavy metal oxide glasses

Multicolor and white light emissions have been achieved in Yb³⁺, Tm³⁺ and Ho³⁺ triply doped heavy metal oxide glasses upon laser excitation at 980 nm. The red (660 nm), green (547 nm) and blue (478 nm) up conversion emissions of the rare earth (RE) ions triply doped TeO₂–GeO₂–Bi₂O₃–K₂O glass (TGBK) have been investigated as a function of the RE concentration and excitation power of the 980 nm laser diode. The most appropriate combination of RE in the TGBK glass host (1.6 wt% Yb₂O₃, 0.6 wt% Tm₂O₃ and 0.1 wt% Ho₂O₃) has been determined with the purpose to tune the primary colors (RGB) respective emissions and generate white light emission by varying the pump power. The involved infrared to visible up conversion mechanisms mainly consist in a three-photon blue up conversion of Tm³⁺ ions and a two-photon green and red up conversions of Ho³⁺ ions. The resulting multicolor emissions have been described according to the CIE-1931 standards.