The X-cut, Y-propagation LiNbO 3 crystals were implanted by 2.8 MeV P + ions with doses of ∼1 x 10 14 ions/cm 2 at room temperature. Planar optical waveguides were formed by P + implantation at doses of 1 × 10 14 , 2 × 10 14 . 3 × 10 14 and 4 x 10 14 ions/cm 2 . Contrary to high-dose ion-implanted waveguides, the extraordinary refractive index was found to increase in the guide region for implantation with low doses by the dark mode. When the light beam was coupled to the LiNbO 3 waveguide which was formed by MeV P + implantation at a dose of 1 x 10 14 ions/cm 2 and a following annealing at 200 °C for 30 min in air, obvious light was found propagating through the entire length of the waveguide, and Rutherford Backscattering (RBS)/channeling technique was used to characterize the lattice reconstruction of LiNbO 3 crystals after the annealing treatment.