Solid state electric field-assisted diffusion has been widely applied to oxide glasses to make buried waveguides but rarely employed in chalcogenide glasses. We have previously fabricated Ag-doped Ge20Ga5Sb10S65 glasses by electric field-assisted diffusion and studied the Ag+ concentration profiles. However, the optical properties after the silver diffusion were left unexplored. In this article, we use the "scratch method" by atomic force microscopy to investigate the refractive index profile of Dy3(+) -doped Ge20Ga5Sb10S65 glass after the silver diffusion. The refractive index profile obtained after the diffusion is very symmetric. An enhanced Dy3+ 1.34 mu m emission has been found only in the presence of silver. The product of measured lifetime and emission cross-section (tau(mea)sigma(e)) is increased by 12% after the diffusion.