Upconversion emission investigation of Tb3+/Yb3+ codoped CdF2 single crystals under infrared laser pump

Tb³⁺/Yb³⁺ co-doped CdF₂ single crystals were successfully fabricated by the Bridgman technique from a vacuum furnace in fluoride atmosphere. The structural and luminescent properties were investigated by X-ray diffraction, optical absorption and luminescence techniques at room temperature. The emission spectra exhibit a weak blue and green emission under 350 nm excitation and a strong emission under 975 nm in the spectral range 450 – 510 nm and 510 – 570 nm which are assigned to ⁵D₄ → ⁷F₆ and ⁵D₄ → ⁷F₅ transitions of Tb³⁺ ions, respectively. Furthermore, the time resolved decay time spectra are also obtained using pulse laser. The obtained upconversion spectra under 940 nm diode laser excitation at different powers showed the two-photon absorption process responsible of blue, green and red emissions.