Direct white light luminescence from Ho3+/Pr3+ co-doped fluoride fiber with blue diode pumping

White light luminescence induced by a blue diode laser was investigated in a double-clad Ho3+/Pr3+ co-doped ZrF4-BaF2-LaF3-AlF3-NaF (ZBLAN) fiber. The pump laser at 442 nm can simultaneously excite Ho3+ and Pr3+ ions, resulting in synergistic luminescence. The emission spectra include multiple visible bands in the blue, green, orange, red, and deep-red spectral regions, which correspond to the 4f-4f electronic transitions of Ho3+ and Pr3+ ions. The relative intensity of emission bands is dependent on the pump power, and the CIE 1931 chromaticity diagram illustrates the dependence of color tunability on the pump power. Under laser excitation at 442 nm, the CIE coordinates are within the white light range, and the CCT values are between 6900 and 8700 K. The results indicate that double-clad Ho3+/Pr3+ co-doped ZBLAN fibers that are directly blue diode-pumped have the potential to be used in high-power white light fiber lasers.