Wavelength tunability of green upconversion luminescence in Er/Yb interlayer-doped silica glass induced by Al ₂ O ₃ modification

Er/Yb-doped silica glasses are promising for three-dimensional displays and optical sensing, but their fixed emission wavelengths limit spectral tunability. Although Al ₂ O ₃ is conventionally used to modify glass networks and suppress rare-earth-ion clustering, here we demonstrate its ability to tune upconversion (UC) emission. Er/Yb interlayer-doped silica glasses with varying Al ₂ O ₃ contents were fabricated by selective laser sintering (SLS). The samples exhibited robust green ( ² H _11/2 , ⁴ S _3/2 → ⁴ I _15/2 ) and red ( ⁴ F _9/2 → ⁴ I _15/2 ) UC emissions. Increasing the Al ₂ O ₃ content shifted the green emission maximum from 500 to 550 nm. This tunability is attributed to Al ₂ O ₃ -induced modifications of the glass network. These results provide a strategy for wavelength-tunable green emission with potential applications in full-color 3D displays and biomedical imaging.