Engineered Second-Order Nonlinearity in Silicon Nitride.
We overcome this drawback and demonstrate a successful induction of χ(2) in Si3N4 through electrical poling with an externally-applied field to align the Si-N bonds. This alignment breaks the centrosymmetry of Si3N4, and enables the bulk χ(2). The sample is heated to over 500°C to facilitate the poling. The comparison between the EO responses of poled and non-poled Si3N4, measured using a Si3N4 micro-ring modulator, shows an enhancement in the amplitude of the measured EO responses as well as a remarkable improvement in its speed from 3GHz to at least 15GHz (3dB bandwidth) after the poling, which confirms the χ(2) nature of the EO response induced by poling.