In this letter we demonstrate broadband electro-optic modulation with frequencies up to 40 GHz in slotted photonic crystal waveguides based on silicon-on-insulator substrates covered and infiltrated with a nonlinear optical polymer. Two dimensional photonic crystal waveguides in silicon enable integrated optical devices with an extremely small geometrical footprint on the scale of micrometers. The slotted waveguide design optimizes the overlap of the optical and electric field in the second order nonlinear optical medium and hence the interaction of the optical and electric wave.
