Spectroscopic ellipsometry was employed to study the optical response of N+ irradiated titanium thin films synthesized by pulsed laser deposition technique. The ellipsometric parameters were measured in the energy range of 1.5 to 5.5 eV. A combined Drude Lorentz (DL) model was employed to quantitatively describe the behavior of the dielectric response as a function of N+ irradiation fluence. A modeling based on effective medium approximation (EMA) was carried out to compute the volume fractions of Ti and TiN from the dielectric response functions. The plasma energy as computed from the DL model, decreased with increasing fluence. The results are explained on the basis of formation of TiN phase which was revealed from grazing incidence X-ray diffraction studies. This was further corroborated from the alterations on volume fraction of titanium as inferred from EMA based computation. (C) 2009 Elsevier B.V. All rights reserved.