Frequency comb generation in a quadratic nonlinear waveguide resonator

Enhancement of a nonlinear optical interaction through waveguides or resonators disclose unconventional interplay among multiple lights. Microresonator-based optical frequency comb (OFC) generation via third order nonlinearity is a typical example of such enhancements. Recently, quadratic-nonlinearity-based OFC with an external cavity configuration has been found and its on-chip implementation is highly demanded. Here we for the first time demonstrate such an on-chip OFC with a quadratic nonlinear waveguide resonator. Furthermore, we controlled the comb spectra separation by adjusting frequency difference of two pump light. This on-chip quadratic device will be useful for not only metrologies but also integrated quantum information technologies. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement