fig8

Figure 8. (A) Upconversion emission of LiNbO₃:Tm³⁺ under two excitation wavelengths. The inset shows the relevant energy levels and optical transitions^[111]. Reproduced from Ref.^[111] with permission from the Elsevier; (B) Upconversion emission spectra of LiNbO₃:Mg²⁺/Ho³⁺ with varying Mg concentrations under 808 nm excitation^[19]; (C) Energy levels of Ho³⁺ ion as well as the proposed upconversion mechanism in LiNbO₃:Mg²⁺,Ho^3+[19]. Reproduced from Ref.^[19] with permission from the Chinese Physics B; (D) CIE coordinates of LiNbO₃:Dy³⁺/Sm³⁺ phosphors under near-UV excitation, with inset photographs taken under 365 nm^[41]. Reproduced from Ref.^[41] with permission from the Elsevier; (E) Temperature-dependent luminescence spectra of LiNbO₃:Sm³⁺ under 402 nm excitation^[114]; (F) Temperature-dependent luminescence spectra of LiNbO₃:Dy³⁺ under 356 nm excitation^[114]. Adapted from Lisiecki et al.^[114] under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. LiNbO₃: Lithium niobate; CIE: Commission Internationale de l’Éclairage; UV: ultraviolet; Tm: thulium; Ho: holmium; Dy: dysprosium; Sm: samarium.