Linearly uncoupled resonators for ultrabroadband resonant frequency doubling on chip

Microresonators serve as powerful platforms for enhancing second-order nonlinear optical interactions, such as second-harmonic generation. Nevertheless, their performance has traditionally been limited by dispersion-related constraints, including phase-matching and doubly resonant conditions, which restrict operation to narrow bandwidths. In this work, we overcome these limitations by demonstrating ultrabroadband resonant frequency doubling in a novel SiN integrated device. The system features an electrically reconfigurable doubly resonant condition and exploits the formation of a photoinduced χ(2) grating to achieve broadband, efficient and tunable nonlinear conversion.