DOI:10.1016/j.cjph.2025.06.030, Abstract: A novel erbium (Er3+)-doped Si rich oxide (EDSRO) thin film embedded with Si nanocrystals (SiNCs) is developed, which shows near-infrared luminescence at lambda = 1540 nm. The EDSRO here makes use of high solubility of Er3+ in SiO2, with SiNCs acting as sensitizers to excite Er3+ions. High photoluminescence quantum yield (PLQY) of the pristine EDSRO is obtained to be 3.3 After treatments of the EDSRO by hydrogen passivation, ytterbium-ions doping, and the introduction of extra SiNCs in sequence, further higher PLQY is achieved to be 20.6 %. Meanwhile, the net optical gain finally attained is 272 cm-1 or 24.3 dB/cm. Both of the PLQY and optical gain are one or two orders of magnitude larger than those of typical erbium-doped Si rich oxides previously reported. The energy transfer efficiency from SiNCs to Er3+ is 11.48 %. The results reported here may find applications in developing highly efficient erbium-doped light sources for optical communication.