Exceptional singular resonance in gain mediated metamaterials

We study the scattering of optical field by a hybridized metamaterial with properly imprinted gain. We predict that an occasionally real-eigen valued singularity in the interaction matrix of the coupled dark-bright meta-molecule would produce a high-Q resonance. This effect is demonstrated in full-wave three-dimensional finite element optical simulation. Field is efficiently amplified at this resonance. Further investigation shows that the resonance is associated with an exceptional point. The difference of this exceptional singularity from other high-Q resonances such as the spectral singularities in the scattering or transfer matrixes of parity-time symmetric systems and the bound states in the continuum is discussed. The non-Hermitian nature of the exceptional singularity promises some nonlinear applications.