Transformation optics

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

Metamaterials in Electromagnetic Wave Absorbers

Abstract: Stealth technology in terms of absorption of electromagnetic waves is a most valuable research area for military purposes. Development of radar absorbing materials (RAM) had been actively researched for a quite long time. In the RAM design, weight, thickness, absorptivity, environmental resistance and mechanical strength are the key factors and therefore development of RAM with low density and high strength is a challenging task. As an alternative, research interest has shifted towards radar absorbing structures (RAS) and metamaterial is one of the lucrative options for the development of RAS. Metamaterials are a new class of ordered composites that exhibit exceptional electromagnetic properties not readily observed in nature. Built from microstructure that is small compared to wavelength of operation, metamaterials can be designed with effective permittivity and permeability values that can be large or small or even negative at any selected frequency. In this review paper, we first place the stealth technology in brief and then concept of metamaterials in context of conventional materials. We then discuss reflection theory of metamaterials from stealth point of view. Next section deals with recent progress towards its application as electromagnetic absorbers and future prospects especially in higher frequency region. Defence Science Journal, 2012, 62(4), pp.261-268 , DOI:http://dx.doi.org/10.14429/dsj.62.1514

Directional invisibility by genetic optimization

Abstract: In this Letter, the design of a directional optical cloaking by a genetic algorithm is proposed and realized experimentally. A three-dimensional finite-difference time-domain method is combined with the genetic optimization approach to generate the cloaking structure to directionally cloak a cylindrical object made of a perfect electrical conductor by suppressing the undesired scattered fields around the object. The optimization algorithm designs the permittivity distribution of the dielectric polylactide material to achieve an optical cloaking effect. Experimental verifications of the designed cloaking structure are performed at microwave frequencies, where the proposed structure is fabricated by 3D printing. The imperfect conformal mapping from a large-scale permittivity distribution and the compensation of the remaining scattering by a small-scale permittivity distribution are the basic physical mechanisms of the proposed optical cloaking.

Core-Shell Particles as Building Blocks for Systems with High Duality Symmetry

Abstract: Material electromagnetic duality symmetry requires a system to have equal electric and magnetic responses. Electromagnetic duality enables technologically important effects like artificial optical activity and zero back-scattering, is a requirement for metamaterials in transformation optics, Huygens wave-front control, and maximal electromagnetic chirality, and appears in topological photonic systems. Intrinsically dual materials that meet the duality conditions at the level of the constitutive relations do not exist in many frequency bands. Nevertheless, discrete objects like metallic helices and homogeneous dielectric spheres can be engineered to approximate the dual behavior. The discrete objects can then be used as building blocks with the objective of obtaining composite systems with high duality symmetry. Here, we exploit the extra degrees of freedom of a core-shell dielectric sphere to obtain a particle whose duality symmetry is more than one order of magnitude better than previously reported non-magnetic objects. We show that the improvement is transferred onto the duality symmetry of composite objects when the core-shell particle is used as a building block instead of homogeneous spheres.

Transformation media based super focusing antenna

Abstract: We propose a new kind of focusing antenna with a large effective diameter based on transformation optics. The device contains a traditional parabolic antenna embedded in a dielectric core and coated by a negative index shell. Numerical simulations are performed to illustrate its advantages.

All-dielectric metasurface for fully resolving arbitrary beams on a higher-order Poincaré sphere

Abstract: Characterizing the amplitude, phase profile, and polarization of optical beams is critical in modern optics. With a series of cascaded optical components, one can accurately resolve the optical singularity and polarization state in traditional polarimetry systems. However, complicated optical setups and bulky configurations inevitably hinder future applications for integration. Here, we demonstrate a metadevice that fully resolves arbitrary beams on a higher-order Poincare sphere (HOPS) via a single-layer all-silicon metasurface. The device is compact and capable of detecting optical singularities and higher-order Stokes parameters simultaneously through a single intensity measurement. To verify the validity of the proposed metadevice, different beams on HOPS0,0 and HOPS1,−1 are illuminated on the metadevices. The beams are fully resolved, and the reconstructed higher-order Stokes parameters show good agreement with the original ones. Taking the signal-to-noise ratio into account, the numerical simulations indicate that the design strategy can be extended to fully resolve arbitrary beams on HOPS with order up to 4. Because of the advantages of compact configuration and compatibility with current semiconductor technology, the metadevice will facilitate potential applications in information processing and optical communications.