Ultralow-threshold thin-film lithium niobate optical parametric oscillator

Materials with strong second-order ( χ ( 2 stretchy="false">) ) optical nonlinearity, especially lithium niobate, play a critical role in building parametric oscillators (OPOs). However, chip-scale integration of low-loss materials remains challenging and limits the threshold power on-chip OPO. Here we report an niobate oscillator at telecom wavelengths using quasi-phase-matched, high-quality microring resonator, whose ∼ 30 width="thickmathspace" µ W is 400 times lower than that previous integrated photonics platforms. An conversion efficiency 11% obtained from pump to signal idler fields 93 µW. The OPO wavelength tuning achieved by varying frequency chip temperature. With lowest among all OPOs demonstrated so far, as well advantages including high efficiency, flexibility quasi-phase-matching, device scalability, thin-film opens new opportunities for chip-based tunable classical quantum light sources provides potential platform realizing photonic neural networks.