White upconversion luminescence in Tm³⁺/Ho³⁺/Yb ³⁺ triply doped K⁺-Na⁺ ion-exchanged aluminum germanate glass channel waveguide

Rare-earth ions doped K⁺-Na⁺ ion-exchanged aluminum germanate (NMAG) glass channel waveguides have been designed and fabricated. Under 980 nm laser pumping, an intense upconversion white light transmission trace was observed in Tm³⁺/Ho³⁺/Yb³⁺ triply doped NMAG glass channel waveguide and a high-brightness light spot was achieved from the output end of the fiber connected to the waveguide channel. The fluorescent colors were diverse and located within or near the white region in CIE chromaticity diagram under various pumping powers. These admirable results indicate that Tm³⁺/Ho³⁺/Yb³⁺ triply doped NMAG channel waveguide is a promising light source for medical and high-precision processing illumination.