Integrated Si3N4 microresonator-based quantum light sources with high brightness using a subtractive wafer-scale platform

The silicon nitride (Si 3 N 4 ) platform, demonstrating a moderate third-order optical nonlinearity and a low optical loss compared with those of silicon, is suitable for integrated quantum photonic circuits. However, it is challenging to develop a crack-free, wafer-scale, thick Si 3 N 4 platform in a single deposition run using a subtractive complementary metal-oxide-semiconductor (CMOS)-compatible fabrication process suitable for dispersion-engineered quantum light sources. In this paper, we demonstrate our unique subtractive fabrication process by introducing a stress-release pattern prior to the single Si 3 N 4 film deposition. Our Si 3 N 4 platform enables 950 nm-thick and 8 μm-wide microring resonators supporting whispering-gallery modes for quantum light sources at 1550 nm wavelengths. We report a high photon-pair generation rate of ∼1.03 MHz/mW 2 , with a high spectral brightness of ∼5×10 6 pairs/s/mW 2 /GHz. We demonstrate the first heralded single-photon measurement on the Si 3 N 4 platform, which exhibits a high quality of conditional self-correlation gH (2) (0) of 0.008 ± 0.003.