Infrared laser imaging based on up-conversion luminescence of SrF2:RE (RE = Er, Tm, Yb, Ho)

At the present time, infrared laser imaging based on up-conversion luminescence is used in different applications. These include bioimaging, biomedicine, infrared microscopy, detection of pollutions and greenhouse gases, solar energy etc. Thereby, in the present paper, we investigated the up-conversion luminescence (UCL) of fluoride phosphors. Fluorite-type SrF2:RE (RE = Er, Tm, Yb, Ho) phosphors were synthesized by co-precipitation from an aqueous nitrate solution technique. Upon laser excitation at 1532, 1645 and 1940 nm UCL of SrF2:RE (RE = Er, Tm, Yb, Ho) phosphors in the visible and near-infrared spectral region were recorded. The rare-earth concentration ions dependence of UCL intensity was studied. Also, we estimated the UCL energy yield in the visible and near-infrared spectral range. Calculated chromaticity coordinates and color temperatures showed that SrF2:RE (RE = Er, Tm, Yb, Ho) phosphors are characterized by the yellow-green and red-orange UCL. The application of up-conversion phosphors for visualization of near-infrared laser radiation is discussed.