We report on Nd:CNGG active planar waveguides produced by 6.0 MeV carbon ion implantation at fluence from 1 x 10(14) ions/cm(2) to 8 x 10(14) ions/cm(2). The refractive index profiles, which were reconstructed according to the measured dark mode spectroscopy, showed that the refractive indices had negative changes in the surface region, forming typical barrier waveguide. The width of waveguide structure induced by carbon ion implantation is similar to 3.8 mm. The typical barrier-shaped distribution may be mainly due to the nuclear energy deposition of the incident ions into the substrate. By performing a modal analysis on the observed TE modes, it was found that the TE0 and TE1 modes can be well-confined inside the waveguide. (C) 2009 Elsevier B.V. All rights reserved.