Transformation optics

About: Transformation optics is a research topic. Over the lifetime, 2687 publications have been published within this topic receiving 102378 citations.

Quantum optical effective-medium theory for loss-compensated metamaterials.

Abstract: A central aim in metamaterial research is to engineer subwavelength unit cells that give rise to desired effective-medium properties and parameters, such as a negative refractive index. Ideally one can disregard the details of the unit cell and employ the effective description instead. A popular strategy to compensate for the inevitable losses in metallic components of metamaterials is to add optical gain material. Here we study the quantum optics of such loss-compensated metamaterials at frequencies for which effective parameters can be unambiguously determined. We demonstrate that the usual effective parameters are insufficient to describe the propagation of quantum states of light. Furthermore, we propose a quantum optical effective-medium theory instead and show that it correctly predicts the properties of the light emerging from loss-compensated metamaterials.

Properties of planar electric metamaterials for novel terahertz applications

Abstract: Planar electric metamaterials are experimentally studied in transmission and reflection utilizing terahertz time-domain spectroscopy. Electrically resonant behavior is observed and provides an estimate of the frequency-dependent transmissivity, reflectivity, and absorptivity of metamaterial composites. Numerical simulations are in good agreement with the measured results and provide additional information helpful in understanding their electromagnetic response. Our results and approach help define the boundaries of a metamaterials-based design paradigm and should prove beneficial in future terahertz applications, particularly with respect to novel filtering, modulation, and switching devices. In addition, this work clarifies some of the mechanisms that limit efficient metamaterials operation at higher-frequencies.

Homogenization Processes and Retrieval of Equivalent Constitutive Parameters for Multisurface-Metamaterials

Abstract: Different procedures are presented for the retrieval of effective constitutive parameters of metamaterial structures realized by multilayer lossless periodic structures. These structures are modeled as Floquet-wave based multiport networks connected by pieces of transmission lines. A generalized Bloch method is then adopted to find the dominant modes of the volumetric homogenized metamaterial. Starting from the results of this analysis, the constitutive tensors of an equivalent homogeneous material are defined. Different levels of equivalence are defined, denoted as “external equivalence,” “dispersion equivalence,” “single-mode equivalence,” and “double-mode equivalence.” The corresponding homogenization processes are characterized by an increasing level of completeness (in the description of the metamaterial behavior) and of sophistication (concerning the processing of the full-wave analysis outcomes). The defined homogenization procedure accounts for dispersion in time (frequency) and space (wavenumber), as well as for anisotropy.

Invisibility Dips of Near-Field Energy Transport in a Spoof Plasmonic Metadimer

Abstract: Invisibility dips, minima in scattering spectrum associated with asymmetric Fano-like line-shapes, have been predicted with transformation optics in studying strong coupling between two plasmonic nanoparticles. This feature of strongly coupled plasmonic nanoparticles holds promise for sensor cloaking. It requires an extremely narrow gap between the two nanoparticles, though, preventing its experimental observation at optical frequencies. Here, the concept of spoof surface plasmons is utilized to facilitate the strong coupling between two spoof-localized-surface-plasmon (SLSP) resonators. Instead of observing in far field, the near-field energy transport is probed through the two SLSP resonators. By virtue of enhanced coupling between the two resonators stacked vertically, a spectral transmission dip with asymmetric Fano-like line-shape, similar to the far-field invisibility dips predicted by transformation optics, is observed. The underlying mode interference mechanism is further demonstrated by directly imaging the field maps of interfered waves that are tightly localized around the resonators. These near-field invisibility dips may find use in near-field sensing, on-chip switching, filters and logical operation elements.