Strong blue, red and near-infrared photoluminescence has been observed from Si+-implanted and pulse-annealed SiO2 layers. Raman scattering and high-resolution electron microscopy analyses have revealed a correlation between the structure of the Si inclusions in the SiO2 matrix and the photoluminescence. Structural transformations in the Si-rich SiO2 layers during pulse and furnace annealing have been discussed in terms of the changes in the light emission observed experimentally. Small Si clusters, non-crystalline inclusions and nanocrystals are believed to be the light sources. The blue, red and near-infrared photoluminescence is associated with small complexes of excess Si atoms, non-crystalline Si nanoinclusions and quantum-confined Si nanocrystals, respectively.