Linear and nonlinear photoluminescence in Ho³⁺, Yb³⁺ doped CaBi₂Nb₂O₉ phosphor for photonic applications

Abstract CaBi 2 Nb 2 O 9 (CBNO) phosphors doped with Ho 3+ and Yb 3+ ions were synthesized through a conventional solid-state reaction technique. The microstructure of the prepared samples was characterized using scanning electron microscopy. The energy bandgap was determined using diffuse reflectance spectroscopy. Down-and up-converted photoluminescence (PL) analyses were conducted to examine the excitation and emission behaviors of the as prepared phosphors, along with the decay lifetimes measurement under 980 nm excitation. Up-conversion (UC) emission spectra revealed emission bands at 545 nm, and 658 nm, which correspond to the 5 F 4 / 5 S 2 to 5 I 8 , and 5 F 5 to 5 I 8 , transitions of Ho 3+ ions, respectively. Analysis of UC emission intensity variation with pump power of 980 nm laser source confirmed the involvement of a two-photon absorption mechanism. The chromaticity coordinates derived from the emission spectra positioned the light emission in the green region. Studies of temperature-dependent PL highlighted the phosphor’s high thermal stability, supported by its notable thermal activation energy. This study shows encouraging results thereby demonstrating the potential of CBNO phosphors for applications in solid-state lighting, display systems, security printing, phototherapy, and other UC-based technologies.