Robustness of bound states in the continuum in anisotropic slab waveguides
Phys. Rev. A 114, 023521 – Published 24 August, 2026
DOI: https://doi.org/10.1103/mybs-w526
Abstract
In wave-guiding structures, a bound state in the continuum (BIC) is a special guided mode with no leakage loss even though lateral radiation channels exist. The BICs are related to high- resonances and have found numerous applications in photonics. A particularly simple class of BICs has been found in slab waveguides with an anisotropic core and anisotropic substrate [Gomis-Bresco et al., Nat. Photon. 11, 232 (2017)]. Many of these BICs are robust with respect to structural parameters. In this paper we demonstrate the robustness of BICs for a broad class of anisotropic waveguides of which the core is nonuniform in general. Using a perturbation method, we show that generic BICs persist when the structure is perturbed with any sufficiently small perturbation satisfying some simple conditions. The theory improves the theoretical understanding of BICs in anisotropic media and provides useful guidance for realizing their practical applications.
