In situ control of integrated Kerr nonlinearity

Abstract: Kerr nonlinearity in nanophotonic cavities provides a versatile platform to explore fundamental physical sciences and develop novel photonic technologies. This is driven by the precise dispersion control and significant field enhancement with nanoscale structures. Beyond dispersion and pump engineering, the direct control of Kerr nonlinearity can release the ultimate performance and functionality of photonic systems. Here, we report the in situ control of integrated Kerr nonlinearity through its interplay with the cascaded Pockels nonlinear process. Kerr nonlinearity is tuned over 10~dB dynamic range without modifying photonic structures. Fano resonance is observed with nonlinear spectrum, in contrast to standard linear transmission. This confirms the quantum interference between competing optical nonlinear pathways. Besides nonlinearity enhancement, we also demonstrate the novel capability to suppress the material intrinsic nonlinearity. Finally, we use the tunable nonlinearity to control the spectral brightness and coincidence-to-accidental ratio of single-photon generation. This work paves the way towards the complete nanoscale control of optical nonlinear processes at quantum level.