Upconversion and color tunability in Tm³⁺/Ho³⁺/Yb³⁺ doped low phonon energy bismuth tellurite glasses

Low phonon energy Tm³⁺/Ho³⁺/Yb³⁺ triply doped bismuth tellurite glasses exhibiting multicolor upconversion fluorescences have been fabricated and characterized. The multicolor fluorescence composed of three primary colors green, red and blue upconversion emissions from Ho³⁺ and Tm³⁺ has been investigated. By adjusting the excitation power, the fluorescence colors can be tuned from multicolor to white color, and the dependence of color tunability on pump power has been presented in the CIE 1931 chromaticity diagram. With the increase in pumping power, the color coordinates move along the down-left direction and hit the equal energy point. The upconversion and color tunability via changing the pump power of infrared excitation in Tm³⁺/Ho³⁺/Yb³⁺ triply doped bismuth tellurite glasses will lead to new breakthrough in the field of three-dimensional solid-state displays and white-light emitting devices.