Layered Babinet complementary patterns acting as asymmetric negative index metamaterial

TL;DR

This paper demonstrates multilayered Babinet complementary patterns that exhibit asymmetric optical responses, negative index behavior, and potential as ultrathin nonreciprocal metamaterials through polarization-dependent experiments.

Contribution

It introduces a novel multilayer design with Babinet complementary miniarrays that act as an ultrathin negative index metamaterial with asymmetric optical properties.

Findings

Observed asymmetric transmission and dichroism dependent on polarization and azimuthal orientation.

Demonstrated negative index behavior with overlapping electric and magnetic dipoles.

Proposed multilayer as a candidate for ultrathin nonreciprocal nanophotonic devices.

Abstract

Azimuthal orientation and handedness dependence of the optical responses, accompanied by asymmetric transmission and asymmetric dichroism, were demonstrated on multilayers constructed with subwavelength periodic arrays of Babinet complementary miniarrays, illuminated by linearly and circularly polarized light. In case of single-sided illumination asymmetric optical responses were observed at the spectral location of maximal cross-polarization that is accompanied by radiative electric dipoles on the nano-objects; whereas negative index material phenomenon was demonstrated, where the electric and magnetic dipoles overlap both spatially and spectrally. The NIM is accompanied by electric multipoles that add up non-radiatively and correlates with the magnetic dipoles characteristic on the nano-entities. By illuminating the multilayer with two counter-propagating circularly polarized beams it was proven that asymmetrical normal component displacement currents at the bounding interfaces arising along flat and tilted bands accompany the asymmetric co-polarized and cross-polarized transmission, respectively. The latter correlates with the asymmetric dichroism in the cross-polarized signal observed in case of single-sided circularly polarized light illumination. The dispersion maps in the single-sided asymmetrical co-polarized reflectance and absorptance indicate flat bands of analogous and complementary extrema, proving the dichroic nature of the observed asymmetric phenomena. The multilayer is proposed as an ultrathin NIM and nonreciprocal nanophotonic element.