We report on the optical planar waveguide formation and modal characterization in Nd: GdVO4 crystals by triple oxygen ion implantation at energies of (2.4, 3.0, and 3.6 MeV) and fluences of (1.4, 1.4, and 3. 1) x 10(14)ions/cm(2). The prism-coupling method is used to investigate the dark-mode property at wavelength of 632.8 nm. The refractive index profiles of the waveguide are reconstructed by an effective refractive index, n(eff) method. The modal analysis shows that the fields of TE modes are well restricted in the guiding region, which means the formation of nonleaky waveguide in the crystal. (C) 2007 Elsevier B.V. All rights reserved.