Resonance in anisotropic layered media

When a periodic anisotropic layered medium is interrupted by a slab of contrasting material, electromagnetic resonance can be manifest in a variety of ways. In one scenario, anisotropy allows for frequency intervals in which waves propagating perpendicular to the layers coexist with evanescent waves. This permits energy to be trapped within the slab at frequencies embedded in the continuous spectrum. These are unstable states that result in resonance under small perturbations. In another scenario, a stationary inflection point in the dispersion relation of an ambient magnetic anisotropic layered medium leads to unidirectional propagation and resonant interaction between Bloch waves and the contrasting layer. Analysis of energetic interactions between waves allows for a detailed understanding of these resonances.