Visible quantum cutting through downconversion in GdPO4:Tb3+ and Sr3Gd(PO4)3:Tb3+

Visible quantum cutting has been observed in GdPO4:Tb3+ upon Tb3+ 4f8–4f75d1 excitation and host excitation, and in Sr3Gd(PO4)3:Tb3+ upon Tb3+ 4f8–4f75d1 excitation. In the quantum cutting process, Tb3+ acts as a quantum cutter, which converts one short wavelength ultraviolet photon or one vacuum ultraviolet photon into more than one visible photon. The quantum cutting involves a cross-relaxation process between two neighboring Tb3+ and direct energy transfer between Tb3+ and Tb3+ or Tb3+ and Gd3+, depending on the excitation wavelength. The quantum efficiency variation of GdPO4:xTb3+ and Sr3Gd(PO4)3:xTb3+ shows a growing trend with increasing of Tb3+ content from x=1.5% to 13%.