Crosstalk in Ti:LiNbO3directional coupler switches caused by Ti concentration fluctuations

We have observed random fluctuations in the local Ti concentration profiles of Ti-diffused LiNbO
3
waveguides. Calculations show that these variations explain the degraded switch extinction ratio (i.e., crosstalk) and other nonideal characteristics observed in LiNbO
3
optical switches. We also demonstrate by calculation a new device configuration for eliminating this source of crosstalk.