Strong energy-transfer-induced enhancement of Er³⁺ luminescence in In₂O₃ nanocrystal codoped silica films

Co-doping of sol-gel processed SiO₂ thin films with Er ³⁺ ions and In₂O₃ nanocrystals produced a 100-fold enhancement of Er³⁺-related 1.54 μm emission compared to films doped only with Er³⁺. Quantitative studies of temperature-dependent photoluminescence spectra show that this dopant-concentration-dependent luminescence enhancement is a result of energy transfer from In₂O₃ to Er³⁺ ions. The dominant nonradiative recombination for Er³⁺ is energy transfer to hydroxyl groups, which is suppressed by proper thermal treatment. These results demonstrate that In₂O₃ nanocrystals have high potential for use as a sensitizer of Er³⁺ ions in high-performance fiber amplifiers.