In this work the refractive index depth profile, its relaxation and the absorption were investigated in 2 MeV proton irradiated PDMS. The above parameters were determined by the spectroscopic ellipsometry technique. The refractive index depth profile follows roughly the shape of the Bragg curve for the penetrating protons. It is shown that the observed difference between the refractive index of the surface (dn = 0.01) and deeper regions (dn = 0.08) is high enough to accomplish waveguiding that is also demonstrated in this paper. This work serves as basis for the production of integrated optical components, e.g. waveguides, gratings or other optical devices, which are planned to be produced by ion irradiation in PDMS. (C) 2011 Elsevier B.V. All rights reserved.