Intense Two Photon Green-Red Upconversion in Er3+/Yb3+/KF/BaO Doped Perovskite SrTiO3 Glass Ceramic

Er³⁺/Yb³⁺ doped perovskite SrTiO₃ matrix was crystallized in borosilicate glass ceramic in order to investigate its optical properties. Powder x-ray diffraction analysis showed two major crystalline phases SrTiO₃ and β-TiO₂, present in the glass ceramic. Particle size in crystalline matrix, calculated by Scherrer’s formula lies in the range of 50-100nm, which was confirmed by SEM micrographs later. Emission spectra of both glass and glass ceramic consisted of two intense green and one red band. Upconversion in glass ceramic was found around 10 times more intense than that in glass. Power dependence studies suggested that 2 excitation photons are participating in various upconversion mechanisms. Transitions ²H_11/2/ ⁴S_3/2→ ⁴I_15/2 and ⁴F_9/2 →⁴I_15/2, responsible for green and red emissions respectively, were visualized through excited state absorption and energy transfer mechanisms.