Transformation optics

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

Physical limitations on metamaterials: restrictions on scattering and absorption over a frequency interval

Abstract: A limitation on the extinction cross section, valid for all scatterers satisfying some basic physical assumptions, is investigated. The physical limitation is obtained from the holomorphic properties of the forward scattering dyadic. The analysis focuses on the consequences for materials with negative permittivity and permeability, i.e. metamaterials. From a broadband point of view, the limitations imply that there is no fundamental difference between metamaterials and ordinary materials with respect to scattering and absorption. The analysis is illustrated by three numerical examples of metamaterials modelled by temporal dispersion.

Multifunctional metasurface: from extraordinary optical transmission to extraordinary optical diffraction in a single structure

Abstract: We show that a metasurface composed of a subwavelength metallic slit array embedded in an asymmetric dielectric environment can exhibit either extraordinary optical transmission (EOT) or extraordinary optical diffraction (EOD). The cascaded refractive indices of the dielectrics can leverage multiple decaying passages into variant subsections with different diffraction order combinations according to the diffraction order chart in the k-vector space, providing a flexible mean to tailor resonance decaying pathways of the metallic slit cavity mode by changing the wavevector of the incident light. As a result, either the zeroth transmission or −1st reflection efficiencies can be enhanced to near unity by the excitation of the localized slit cavity mode, leading to either EOT or EOD in a single structure, depending on the illumination angle. Based on this appealing feature, a multifunctional metasurface that can switch its functionality between transmission filter, mirror, and off-axis lens is demonstrated. Our findings provide a convenient way to construct multifunctional miniaturized optical components on a single planar device.

Programmable Extreme Chirality in the Visible by Helix-Shaped Metamaterial Platform

Abstract: The capability to fully control the chiro-optical properties of metamaterials in the visible range enables a number of applications from integrated photonics to life science. To achieve this goal, a simultaneous control over complex spatial and localized structuring as well as material composition at the nanoscale is required. Here, we demonstrate how circular dichroic bands and optical rotation can be effectively and independently tailored throughout the visible regime as a function of the fundamental meta-atoms properties and of their three dimensional architecture in a the helix-shaped metamaterials. The record chiro-optical effects obtained in the visible range are accompanied by an additional control over optical efficiency, even in the plasmonic context. These achievements pave the way toward fully integrated chiral photonic devices.

A Broadband Negative Index Metamaterial at Optical Frequencies

Abstract: A broadband metamaterial presenting negative indices across hundreds of nanometers in the visible and near-infrared spectral regimes is demonstrated theoretically, using transformation optics to design the metamaterial constituents. The approach begins with an infinite plasmonic waveguide that supports a broadband but dark (i.e, not easily optically accessed) negative index mode. Conformal mapping of this waveguide to a finite split-ring-resonator-type structure transforms this mode into a bright (i.e, efficiently excited) resonance composed of degenerate electric and magnetic dipoles. A periodic array of such resonators exhibits negative refractive indices at optical frequencies in multiple regions exceeding 200 nm in bandwidth. The metamaterial response is confirmed through simulations of plane-wave refraction through a metamaterial prism. These results illustrate the power of transformation optics for new metamaterial designs and provide a foundation for future broadband metamaterial devices.

Liquid crystals, photonic crystals, metamaterials, and transformation optics

Abstract: Recent advances of modern optics have been made possible with the development of unique materials, most notably liquid crystals (LCs), photonic crystals (PCs), and metamaterials (MMs). LCs have already completed a revolution in the way we present information nowadays, enabling an entire industry of flat panel liquid crystal displays (LCDs). PCs (1) and MMs (2) are further behind in terms of broad commercialization, but the change they produce in our understanding of how matter can control light is no less revolutionary, fueling dreams that only recently were science fiction, such as subwavelength imaging and focusing, invisibility cloaking, black hole-like light trapping, and more. PCs and MMs are formed by building units of a size s intermediate between the molecular scale m = (1–3) nm and the optical wavelength λ and cannot be simply synthesized as small organic molecules that form LCs. Design, manufacturing, and control of properties of PCs and MMs at the scale m < s ≤ λ is the major challenge. There are a variety of ways by which the LCs can help in the development of PCs and MMs; one of the latest advances is presented in PNAS by Ravnik et al. (3).