Open boundary conditions for the simulation of leaky modes

We propose an open-boundary method for the simulation of the modes of confining dielectric structures. The technique is inclusive of normal modes, but is especially advantageous for the simulation of quasi-normal, or leaky, modes. The central idea is to utilize the asymptotic form of targeted solutions to eliminate the outer part of the computational domain and bring the numerical boundary close to the simulated structure. While a similar approach was previously demonstrated for scalar quantum models, here we put forward a generalization for fully vectorial fields. Accuracy in this new context is validated using step-index and tube-type hollow core fiber geometries. The method has broad applicability, as quasi-bound modes are intrinsic to many systems of interest in optics and photonics.