Transformation optics

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

Transformation Optics Inspired Multibeam Lens Antennas for Broadband Directive Radiation

Abstract: Recent advancements in transformation optics (TO) and metamaterials have inspired tremendous interest in the electromagnetic community, creating a variety of novel antennas with enhanced performance, such as broad bandwidth, large gain, and high polarization efficiency. Although there could be infinitely many transformations for designing a given device, most of them result in rather complicated material compositions. This paper compares two recently introduced TO techniques, both of which lead to much simpler material requirements. In particular, a linear geometrical transformation or a quasi-conformal mapping was employed to design multi-beam collimating lenses, which possess either homogeneous or isotropic constituent materials. A systematic comparison is made for the first time between these two TO design approaches for a specific example of a quad-beam focusing lens, where the advantages and disadvantages of each method are clearly identified. Full-wave numerical simulations were performed to demonstrate the well-collimated beams produced by the TO lenses designed by either transformation. The characteristics of the two lens antennas, such as radiation pattern and bandwidth, were contrasted, providing valuable guidance on design tradeoffs for a specific application.

Independent Manipulation of Heat and Electrical Current via Bifunctional Metamaterials

Abstract: Spatial tailoring of the material constitutive properties is a well-known strategy to mold the local flow of given observables in different physical domains. Coordinate-transformation-based methods (e.g., transformation optics) offer a powerful and systematic approach to design anisotropic, spatially-inhomogeneous artificial materials ("metamaterials") capable of precisely manipulating wave-based (electromagnetic, acoustic, elastic) as well as diffusion-based (heat) phenomena in a desired fashion. However versatile these approaches have been, most designs have so far been limited to serving single-target functionalities in a given physical domain. Here we present a step towards a "transformation multiphysics" framework that allows independent and simultaneous manipulation of multiple physical phenomena. As a proof of principle of this new scheme, we design and synthesize (in terms of realistic material constituents) a metamaterial shell that simultaneously behaves as a thermal concentrator and an electrical "invisibility cloak". Our numerical results open up intriguing possibilities in the largely unexplored phase space of multi-functional metadevices, with a wide variety of potential applications to electrical, magnetic, acoustic, and thermal scenarios.

Goos-Hänchen effect in epsilon-near-zero metamaterials

Abstract: Light reflection and refraction at an interface between two homogeneous media is analytically described by Snell's law. For a beam with a finite waist, it turns out that the reflected wave experiences a lateral displacement from its position predicted by geometric optics. Such Goos-Hanchen (G-H) effect has been extensively investigated among all kinds of optical media, such as dielectrics, metals, photonic crystals and metamaterials. As a fundamental physics phenomenon, the G-H effect has been extended to acoustics and quantum mechanics. Here we report the unusual G-H effect in zero index metamaterials. We show that when linearly polarized light is obliquely incident from air to epsilon-near-zero metamaterials, no G-H effect could be observed for p polarized light. While for s polarization, the G-H shift is a constant value for any incident angle.

Implementing Quantum Search Algorithm with Metamaterials.

Abstract: Metamaterials, artificially structured electromagnetic (EM) materials, have enabled the realization of many unconventional EM properties not found in nature, such as negative refractive index, magnetic response, invisibility cloaking, and so on. Based on these man-made materials with novel EM properties, various devices are designed and realized. However, quantum analog devices based on metamaterials have not been achieved so far. Here, metamaterials are designed and printed to perform quantum search algorithm. The structures, comprising of an array of 2D subwavelength air holes with different radii perforated on the dielectric layer, are fabricated using a 3D-printing technique. When an incident wave enters in the designed metamaterials, the profile of beam wavefront is processed iteratively as it propagates through the metamaterial periodically. After ≈N roundtrips, precisely the same as the efficiency of quantum search algorithm, searched items will be found with the incident wave all focusing on the marked positions. Such a metamaterial-based quantum searching simulator may lead to remarkable achievements in wave-based signal processors.

Design of High-Gain Lens Antenna by Gradient-Index Metamaterials Using Transformation Optics

Abstract: Transformation of space coordinates can be used as a convenient tool for producing a controlled electromagnetic field pattern. In this paper, using a conformal transformation, the design procedure of a lens antenna with high gain and low sidelobes is presented which can be realized by isotropic graded refractive index (GRIN) materials. Applying proper simplifying techniques, the designed lens can be made by non-resonant metamaterials or non-magnetic dielectrics having wide frequency band and low loss. A graded photonic crystal (GPC) operating in metamaterial regime is used for this purpose. By placing the lens in a horn antenna, a highly directive beam is achieved. It is also shown that by lateral displacement of the lens medium, the beam direction can be controlled to some extent. A multibeam antenna in which each beam can be controlled independently is also presented. Simulation results are used to justify the design approach.