Sm³⁺ photoluminescence and excited-state dynamics in lithium-barium borate glasses co-doped with CuO

The effect of CuO co-doping on orange/red-emitting Sm³⁺-doped borate glasses prepared by melting was investigated by various spectroscopic techniques. The glasses were first characterized by X-ray diffraction and Fourier transform-infrared spectroscopy for basic structural properties. Absorption spectroscopy showed that CuO addition leads to the development of the Cu²⁺ absorption band around 735 nm. Photoluminescence (PL) spectra obtained for the CuO-free reference glass under 250 nm excitation displayed host-sensitized Sm³⁺ PL along with intrinsic band emission from the borate host. The CuO doping produced a new contribution to band emission characteristic of Cu⁺. Further, significant decrease of Sm³⁺ visible luminescence was evidenced in accord with a quenching effect induced by Cu²⁺. The analysis of Sm³⁺ emission decay curves harmonized with the occurrence of two populations of Sm³⁺ ions (single, interacting). The two decay components showed significant ⁴G_5/2 lifetime decrease with increasing CuO content demonstrating an efficient Sm³⁺ → Cu²⁺ energy transfer.