ObjectiveSqueezed states are an important resource in quantum information processing. Utilizing squeezed light can enhance the sensitivity of physical measurements and surpass the standard quantum limit, making it an indispensable element in quantum information science. Integrated photonics chips provide a reliable and easily scalable research platform for generating squeezed states, and the high stability and reproducibility of modern lithographic techniques offer hope for achieving large-scale quantum technologies. The four-wave mixing process based on silicon nitride micro-ring resonators is an important approach for generating squeezed states. The main factors limiting the generation of on-chip high-level-squeezing include micro-ring resonator design, nonlinear noise, and, especially, photonic loss. To further improve the level of squeezing generated on-chip, the preparation of low-loss or high-Q silicon nitride micro-ring resonators is particularly crucial.MethodsIn this work, we employed low-pressure chemical vapor deposition (LPCVD) to deposit high-quality silicon nitride films. To achieve micro-ring resonators with varying states of coupling, we designed a series of micro-ring resonators with different coupling gaps. Using scanning electron microscopy, we optimized both the deposition process of high-quality silicon nitride films and the etching process of micro-ring resonators on the silicon nitride platform. As a result, we successfully fabricated low-loss silicon nitride micro-ring resonators with various sizes and structures. We also set up a testing system for the micro-ring resonators, using lensed fibers for end-face coupling with the chip. Then, we experimentally characterized these micro-rings and systematically analyze their transmission spectra, coupling regimes, and quality factors.Results and DiscussionsResults show that the prepared micro-ring resonators have similar intrinsic quality factors. Notably, the intrinsic quality factor of the micro-ring resonator with a cross-sectional size of 2000 nm × 290 nm reaches 1.5×10⁶, corresponding to a waveguide transmission loss of 0.23 dB/cm. Theoretical calculations indicate that this structure can optimally generate squeezed states with up to 9 dB of squeezing. When the total efficiency is 40%, approximately 2 dB of squeezing can be observed experimentally.ConclusionsIn this work, we fabricate silicon nitride micro-ring resonators with high quality factors. After optimizing the fabrication process, the quality factor of the micro-ring resonators can reach up to 1.5×10⁶. Theoretical calculations suggest that this could enable the direct observation of squeezed states with approximately 2 dB of squeezing. This study provides an experimental foundation for on-chip generation of high-quality continuous variable squeezed states, thus paving the way for future advancements in integrated quantum photonics.