Bottom-up nanocolloidal metamaterials and metasurfaces at optical frequencies

Abstract

Metamaterials and metasurfaces are artificial composite media engineered to exhibit extraordinary properties of wave propagation. In bulk (3D) metamaterials, such extreme properties may result from non-conventional values of effective homogeneous optical parameters such as the electric permittivity and the magnetic permeability. These features generally originate in the collective response of the constitutive structural elements, which have to be of sub-wavelength dimensions to satisfy the requirement of optical homogeneity, and which have to be highly polarizable to provide efficient optical functions. For visible light applications, sub-wavelength dimensions imply structuration at the nanoscale whereas high polarizability can be achieved by optical resonators such as plasmonic or Mie resonators. Metasurfaces, on the other hand, are 2D equivalent of metamaterials, designed to control the phase, amplitude and possibly polarization of incident EM waves with subwavelength thickness, using interfacial discontinuities effects. This review shows how the bottom-up approach based on nano-chemistry and the self-assembly methods of colloidal physical-chemistry can be used to produce nano-sized tunable magneto-electric resonators which can subsequently be assembled in bulk nanostructured metamaterials as well as in optically thin metasurfaces. Focusing mainly on work carried out at the University of Bordeaux over the past decade, we review some of the optical properties observed in visible light from the fabricated systems. Specific optical experiments and numerical simulations are of crucial importance for the design of the most efficient structures and the extraction of the effective optical parameters.

Keywords

• Metamaterials
• Metasurfaces
• Self-assembly
• Colloids
• Bottom-up
• Optical resonances