Metamaterials for optical and THz ranges: design and characterization

Abstract

The thesis is devoted to the field of metamaterials (MtMs) - effectively continuous artificial composites with advantageous electromagnetic properties not normally met in nature. The main goal of the work is the engineering of MtMs with new and extreme electromagnetic properties and their electromagnetic characterization.

The first part of the thesis is focused on the artificial magnetism and isotropic negative permittivity and permeability in the near-infrared and visible ranges. Several design solutions based on resonant complex-shaped inclusions are proposed and studied analytically and numerically. In the first design utilization of clusters of plasmonic dimers leads to the negative permeability in the near-infrared range. Next suggested MtM consisting of the clusters of plasmonic triangular nanoprisms possesses isotropic negative permeability on the boundary between the near-infrared and visible ranges. The third design based on core-shell metal-dielectric particles allows for the isotropic negative refractive index in the near-infrared range.

The second part of the thesis is devoted to the problem of characterization of planar and bulk MtMs. At first, the applicability of the so-called Holloway-Kuester method is studied for the planar arrays of complex inclusions. It is shown, that despite the fact that the approach initially was developed for the arrays of solid particles in the quasi-static approximation, it is also applicable for the arrays of rather optically substantial resonant clusters of plasmonic nanoparticles. Then, the method of homogenization of bulk MtMs is suggested, based on the account of electromagnetic interaction between crystal planes forming an orthorhombic lattice. The method reveals the electromagnetic properties not covered by the standard quasi-static homogenization procedures.

The last research problem studied in the thesis is the engineering of planar multifunctional MtMs for the THz range. The suggested MtM consists of resonant metal stripes put on both sides of an elastic polymer film and allows for the combination of polarization transformation properties with sensitivity to the applied strain. The design is studied theoretically, numerically, and experimentally. For the last purpose an original fabrication method is developed, allowing for the rather simple creation of optically large samples. The fabricated sample experimentally demonstrates a high sensitivity to stretching in the transmission coefficient for the co-polarized field.