Visualization of 2-μm radiation by BiF3:Ho3+ and BiF3:Ho3+/Yb3+ ceramics

A series of ceramic samples of the compositions BiF3:1%Ho3+, BiF3:4%Ho3+, BiF3:1%Ho3+ + 1%Yb3+, and BiF3:1%Ho3+ + 3%Yb3+ is synthesized and the conversion of Tm:YLF laser radiation (λ = 1908 nm) is studied. The luminescence spectra exhibit bands in the regions of 490, 545, and 650 nm. The kinetic measurements of the afterglow of the green and red bands show that the population of the 5S2 and 5F4 states in the BiF3:1%Ho3+ samples occurs due to successive absorption of excitation photons, while the 5F5 level of Ho3+ is populated due to the ion–ion interaction. Codoping with Yb3+ leads to a decrease in the visualization threshold power density to 2 W/cm2.