Diabolical points in coupled ridge resonators

In this paper, the resonant optical properties of two coupled ridges on the surface of a single-mode dielectric slab waveguide are theoretically investigated. The diabolical points of a structure can be achieved by near-field coupling and far-field interference of resonance modes in the ridges. The uniform unity transmission and 2 pi spectral phase span are demonstrated around the diabolical points. By using the temporal coupled-mode theory, we analyze the generating conditions of diabolical points in coupled ridges and the corresponding group delay around diabolical points. The influences of optical loss and excitation beam width on the optical response at diabolical points of a structure are also discussed. Diabolical points in the waveguide system have potential applications in dispersion compensation and phase-only modulators in integrated optical circuits. (c) 2023 Optica Publishing Group