Computation of scattering resonances in absorptive and dispersive media with applications to metal-dielectric nano-structures

In this paper we consider scattering resonance computations in optics when the resonators consist of frequency dependent and lossy materials, such as metals at optical frequencies. The proposed computational approach combines a novel hp-FEM strategy, based on dispersion analysis for complex frequencies, with a fast implementation of the nonlinear eigenvalue solver NLEIGS. Numerical computations illustrate that the pre-asymptotic phase is significantly reduced compared to standard uniform h and p strategies. Moreover, the efficiency grows with the refractive index contrast, which makes the new strategy highly attractive for metal-dielectric structures. The hp-refinement strategy together with the efficient parallel code result in highly accurate approximations and short runtimes on multi processor platforms. •Fast and accurate computation of scattering resonances for lossy resonators.•Dispersion analysis of high order FE for Helmholtz problems with complex frequencies.•Novel hp-FE a-priori strategies result in a shorter pre-asymptotic phase of the error.•Convergence studies illustrate the effectiveness of the proposed solution strategies