We have designed, fabricated, and demonstrated a unique integrated PPLN switched directional couplers and polarization mode converters in Ti:LiNbO3 waveguides. A completely crossover coupling was obtained from such a device with a six-domain-inversion coupling section of 6mm long and a waveguide spacing of 4.5 μm when an external voltage of 200 V was applied along the crystal z axis. A completely crossover coupling can also be observed with other samples with single-domain and other multiple-domain-inversion configurations. We found in general, a device with higher number of domain inversions in the coupling section will have a less constraint on the coupling length for a completely crossover coupling and can perform more times of crossover couplings with EO tuning. We also successfully demonstrated the unique capability of this PPLN Ti:LiNbO3 waveguide device where the polarization mode and the directional coupling can be EO switched simultaneously or separately to increase its device functionality and applicability.
