A thin film polymer device including a waveguide core surrounded by dielectric material positioned on a platform. The core has a passive input portion and a passive output portion joined by a necked down active portion. A layer of EO polymer material positioned on the dielectric material overlying the active portion of the core and the core, the EO polymer, and the dielectric material all having refractive indices with the refractive index of the EO polymer being higher than the refractive index of the dielectric material. Light progressing through the core from the passive input portion to the passive output portion transitions to the layer of EO polymer material as it enters the necked down active portion and transitions back to the core as it leaves the necked down active portion.