An electrooptical channel waveguide array was constructed in potassium lithium tantalate niobate substrate by the implantation of He(+) ions at high energies. The array was fabricated by two successive implantation sessions at 1.6 MeV and 1.2 MeV through a comb-like stopping mask that limited the implanted ions to penetrate the substrate in 1 microm wide stripes periodically distributed at 3.5 microm intervals. This generated a grating of amorphized stripes with reduced refractive index. This was followed by a uniform implantation of He(+) ions at 1.8 MeV which created a bottom cladding layer below the array. Wave propagation in the array was studied by focusing a light beam at 636 nm into the central channel, and observing the wavefront it created at the output plane of the array. It was found that applying an electric field across the array strongly affects the coupling between adjacent channels and governs the width of the wavefront at the output plane.