Planar and channel optical waveguides were fabricated in Cu doped KTiOPO4 (KTP) substrates using Rb+:K+ ion exchange process and annealing process. The effective refractive indices were measured using the m-line method and the refractive index profiles of these waveguides were calculated using the inverse WKB method. For waveguides in Cu:KTP substrates the difference of diffusion depth d and index change Δn at the z- and z+ surfaces can hardly be observed. This observation is different from KTP. Compared with undoped KTP substrates the diffusion depth d at the z- surfaces is larger, whereas the index change Δn is smaller. At the z+ surfaces both d and Δn are larger. The light induced effective index changes in Cu doped KTP channel waveguides were measured at 0.476, 0.488, 0.514, 0.6328, and 0.83 μm wavelengths. No changes were observed at the power flow of 1×108 W/m2, revealing that Cu ion does not play an important role in photorefractive effect of KTP crystals. © 1997 American Institute of Physics.