Coupled-wave formalism for bound states in the continuum in guided-mode resonant gratings

Abstract

We present simple yet extremely accurate coupled-wave models describing the formation of bound states in the continuum (BICs) in 1D-periodic guided-mode resonant gratings (GMRGs) consisting of a slab waveguide layer with a binary grating attached to one or both of its interfaces. Using these models, we obtain simple closed-form expressions predicting the locations of the BICs and quasi-BICs in the $\omega$-$k_x$ parameter space. We study two mechanisms of the BIC formation: coupling between two counter-propagating guided modes and coupling between a guided mode and a Fabry-Pérot mode. The BIC conditions for the two considered mechanisms are formulated in terms of the scattering coefficients of the binary grating. The predictions of the presented models are in excellent agreement with the results of rigorous numerical simulations obtained using the Fourier modal method.

9 pages, 5 figures

References in corpus (4)

• Topological nature of bound states in the radiation continuum
• Bloch bound states in the radiation continuum in a periodic array of dielectric rods
• Numerical methods for calculating poles of the scattering matrix with applications in grating theory
• Polarized bound state in the continuum and resonances with tunable Q-factor in an anisotropic photonic crystal

Cited by in corpus (1)

• Topologically protected bound states in the continuum and strong phase resonances in integrated Gires-Tournois interferometer