High performance of two-wave mixing in a BaTiO3 waveguide realized by He+ implantation

Two-wave mixing in a He+-implanted waveguide fabricated with it BaTiO3 subs trate is investigated at 514.5 nm. The study is conducted for several direc tions of the grating vector relative to the optical c axis. The maximum gai n of 58 cm(-1) is far higher than the value of 15 cm(-1) that is measurable in the same conditions in bulk samples. Taking into account the mode losse s, we show that the experimental values for the gain are in good agreement with theory. The feasibility of photorefractive interactions between TE gui ded waves with different mode orders is demonstrated. The characteristics o f the photorefractive effect in the waveguide are shown to be different fro m those in the bulk (opposite transfer direction, shorter response time), w hich suggests that the nature of the dominant charge carriers and the elect ro-optic properties are modified by the implantation. (C) 1999 Optical Soci ety of America [S0740-3224(99)02611-9].