Intensity difference squeezing in a strongly overcoupled silicon nitride microresonator

Journal article, 2026

Integrated nonlinear microring resonators are promising sources of bright twin-beams exhibiting intensity difference squeezing. To take advantage of the noise reduction of these quantum states, many applications require high squeezing levels. However, the attainable on-chip squeezing is constrained by the ratio of intrinsic to coupling loss, which is strongly related to design and fabrication limits. Here, we demonstrate a silicon nitride microring resonator engineered to enable a set of periodic strongly overcoupled resonances from which the estimated on-chip intensity difference squeezing is 11.8 dB, exceptionally high for an integrated device. Due to significant setup loss, we directly measure 1.4 +/- 0.2 dB of squeezing, corresponding to an on-chip level of 9.2 +/- 5.1 dB. In addition, the new, to the best of our knowledge, design inherently suppresses mode competition in the modes surrounding the twin-beams, enabling a constant high squeezing level up to moderate powers. These results represent a significant step toward the miniaturization of integrated devices whose performance benefits from surpassing the quantum noise limit using squeezed states, with particular relevance to sensing applications. Published by Optica Publishing Group under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.