On-chip χ² microring optical parametric oscillator

Optical parametric oscillators (OPOs) have been widely used for decades as tunable, narrow linewidth laser sources for reaching long wavelengths and are attractive for applications such as quantum random number generation and Ising machines. To date, OPO lasers have been realized in traditional bow-tie laser cavities and millimeter-sized whispering gallery mode resonators fabricated from χ² materials such as lithium niobate. With the advance in integrated photonic techniques demonstrated by ultra-efficient second harmonic generation in aluminum nitride (AlN) photonic circuits, highly compact and stable chip-scale implementation of OPO lasing is feasible. Here, we employ phase-matched AlN microring resonators to demonstrate low-threshold OPO lasing in the telecomm infrared band with an on-chip efficiency up to 17% and milliwatt-level output power. A broad phase-matching window is observed, enabling tunable generation of signal and idler pairs over a 180 nm bandwidth across the C band. This result establishes an important milestone in integrated nonlinear optics and paves the way towards chip-based quantum light sources and tunable lasers for spectroscopy and chemical sensing.