Optical properties of metamaterials: Influence of electric multipoles, magnetoelectric coupling, and spatial dispersion

We present a study on the optical properties of metamaterial layers containing U-shaped resonators with resonances in the near infrared. We show that the description of the optical properties requires taking into account permittivity, permeability, and chirality tensors. The elements of these tensors were tentatively attributed to surface plasmon resonances of the arms, magnetoelectric coupling, and spatial dispersion. We show that measurements of the Mueller matrix of the sample in appropriately chosen conditions allow unambiguous discrimination of the contribution of the different elements of the tensors to the optical properties of the metamaterial. Emphasis is put on the description of transfers of polarization and symmetries among the Mueller matrix elements. The findings of the theoretical part are confirmed by spectroscopic ellipsometric measurements made on this sample. The spectral dispersion of the different elements of permittivity, permeability, and chirality, modeled using oscillators with Lorentzian line shape, allows correct adjustment of measurements.