Up‐conversion luminescence of ytterbium and thulium codoped potassium yttrium double tungstate crystal

Thulium and ytterbium co‐doped double tungstate Yb³⁺,Tm³⁺: NaY(WO₄)₂ single crystals were prepared by using RF‐heating Czochralski (CZ) pulling method. Its polarized transmittance spectra have been recorded in the region of 290‐2000 nm at room temperature. The energy levels transitions were assigned to the corresponding absorption line. The up‐conversion luminescences at 793 nm and 475 nm were measured when the sample were pumped by 972 nm LD and the energy transfer mechanism between Yb³⁺ and Tm³⁺ ions was analyzed.