Silicon photonics has attracted a lot of interest in recent years. The mature silicon technology has made silicon-on-insulator (SOI) an attractive material system for high density photonic integration. Specifically, the high refractive index and low absorption of silicon at telecommunication wavelengths allows for excellent optical mode confinement and guiding. However, second-order nonlinear optical functionalities cannot be realized easily when relying on the intrinsic properties of silicon, due to its centrosymmetric crystal structure. By combining the excellent high-index guiding properties of SOI waveguides with the intrinsically ultrafast electro-optic (EO) effect of organic materials, ultrafast tuning in very compact devices seems feasible. Recently, highly responsive modulators with slotted silicon waveguide configurations have been demonstrated [1,2]. © 2011 IEEE.