In situ control of effective Kerr nonlinearity with Pockels integrated photonics

Nanophotonic cavities with Kerr nonlinearities are a versatile platform both to explore fundamental physics and to develop practical photonic technologies(1-3). This is possible because nanoscale structures allow precise dispersion control and provide significant field enhancement. To improve the functionality and performance of photonic devices even further, direct control of the Kerr nonlinearity would be desirable. Here, we report the in situ control of integrated Kerr nonlinearity through its interplay with the cascaded second-order nonlinear process(4-9). We observe a Fano resonance in the nonlinear spectrum rather than in the linear transmission(10), confirming the quantum interference between competing optical nonlinear pathways. The Kerr nonlinearity is tuned over a dynamic range of 10 dB without modifying the photonic structure. We also demonstrate the suppression of the intrinsic material nonlinearity and we use the tunable nonlinearity to control the spectral brightness and coincidence-to-accidental ratio of single-photon generation.