Coupling Ideality of Integrated Planar High-QMicroresonators

Photonic integrated circuits for linear, nonlinear, and quantum optics rely on microresonators, which enable complex filters and high-speed modulators, efficient parametric processes at low input power, and generation of squeezed light and correlated photons. Systematically measuring integrated Si₃N₄ optical microresonators, the authors identify the high impact of design-dependent losses on device performance. Fully three-dimensional simulations reveal the origin of this loss to be poor resonator-waveguide coupling, which could be minimized thanks to the insight from this study.