TE-TM mode splitter using directional coupling between heterogeneous waveguides in LiNbO/sub 3/

We propose and demonstrate a novel passive TE-TM mode splitter using an anomalous directional coupler consisting of Ti-diffused and annealed, proton-exchanged waveguides in LiNbO/sub 3/. The extraordinary wave was successfully power-transferred to the cross output with the extinction ratio of >12 dB in both X- and Z-cut LiNbO/sub 3/. The ordinary wave experienced no power transfer without any excess loss due to side-way diffusion of Ti or proton. The coupler length was only <1 mm at /spl lambda/=0.813 mm, which was short enough for optical integration.< >