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 substrate is investigated at 514.5 nm. The study is conducted for several directions of the grating vector relative to the optical c axis. The maximum gain 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 losses, we show that the experimental values for the gain are in good agreement with theory. The feasibility of photorefractive interactions between TE guided waves with different mode orders is demonstrated. The characteristics of the photorefractive effect in the waveguide are shown to be different from those in the bulk (opposite transfer direction, shorter response time), which suggests that the nature of the dominant charge carriers and the electro-optic properties are modified by the implantation. (C) 1999 Optical Society of America [S0740-3224(99)02611-9].