1　at%　Dy3+:　CaF2　and　1　at%　Dy3+/5　at%　Y3+:　CaF2　crystals　were　grown　by　Bridgman　method.　Absorptions,　visible　and　mid-infrared　emissions,　and　fluorescence　decay　curves　were　measured.　By　applying　Judd-Ofelt　(J-O)　theory,　for　Dy3+/Y3+:　CaF2　crystal　stronger　oscillator　strength　and　radiation　transition　probability　were　derived.　The　effect　of　Y(3+)ions　incorporation　into　CaF2　crystals　on　the　light　emission　of　Dy3+　ions　was　discussed.　Co-doped　Y3+　ions　can　destroy　Dy　clusters,　cripple　the　concentration　quenching　effect,　and　enhance　the　yellow　and　mid-infrared　fluorescence　intensity.　The　yellow　fluorescence　intensity　of　Dy3+/Y3+:　CaF2　is　similar　to　70　times　higher　than　that　of　Dy3+:　CaF2　crystal.　The　local　structure　of　Dy3+　ions　was　analyzed,　and　co-doping　Y3+　can　increase　the　quantity　of　tetragonal　Dy　clusters.　In　Dy3+/Y3+:　CaF2　crystal,　the　tetragonal　Dy　clusters　occupy　the　dominant　position,　and　the　fluorescence　lifetime　(tau(f))　is　relatively　short.　It　can　be　concluded　that　Dy3+:　CaF2　and　Dy3+/Y3+:　CaF2　crystals　are　expected　to　achieve　yellow　and　mid-infrared　laser　output　simultaneously.　(C)　2020　Elsevier　B.V.　All　rights　reserved.