From Electromagnetically Induced Transparency to Superscattering with a Single Structure: A Coupled-Mode Theory for Doubly Resonant Structures

We observe from simulations that a doubly resonant structure can exhibit spectral behavior analogous to electromagnetically induced transparency, as well as superscattering, depending on the excitation. We develop a coupled-mode theory that explains this behavior in terms of the orthogonality of the radiation patterns of the eigenmodes. These results provide insight in the general electromagnetic properties of photonic nanostructures and metamaterials.

Figure 1

Doubly resonant structures can exhibit behavior that is (a),(b) a classical analogue of EIT, as well as (c),(d) akin to superscattering in their transmission cross section spectra, depending on the excitation. Theory (blue line) matches finite-difference frequency-domain simulations (red dots). The insets show the simulated double-slit structure with broken symmetry (permittivities of materials in the slits are 40 and 40.16) and the incident plane wave. The dashed lines correspond to the Lorentzian transmission cross section spectra of the individual slits.

Figure 2

(a) Two deep-subwavelength slits spaced a distance $d$ couple to an outgoing plane wave (under an angle $\theta$ with the normal) with phase difference $\varphi$. The slits are assumed to be isotropic radiators. (b) Overlap between the radiation patterns of the individual radiators.

Figure 3

Transmission cross section spectra for (a) perfect omnidirectional EIT and (b) omnidirectional superscattering.