Transformation optics

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

Manipulating scattering features by metamaterials

Abstract: We present a review on manipulations of electromagnetic scattering features by using metamaterials or metasurfaces. Several approaches in controlling the scattered fields of objects are presented, including invisibility cloaks and radar illusions based on transformation optics, carpet cloak using gradient metamaterials, dc cloaks, mantle cloaks based on scattering cancellation, “skin” cloaks using phase compensation, scattering controls with coding/programmable metasurfaces, and scattering reductions by multilayered structures. Finally, the future development of metamaterials on scattering manipulation is predicted.

Double negative elastic metamaterial design through electrical-mechanical circuit analogies

Abstract: Previous studies into solid elastic metamaterials which have a simultaneously negative effective bulk modulus and density have proposed designs for materials with relatively narrow bandwidths, because of the reliance on resonators to provide the dispersive material properties. Some of the proposed novel applications for metamaterials, such as invisibility cloaks and sub-wavelength lenses, generally require materials with inherently larger bandwidths for practical exploitation. In this paper, a well-known electromagnetic metamaterial design is used together with the electrical-mechanical circuit analogies to propose a simultaneously double negative elastic metamaterial design which does not suffer from the narrow bandwidth constraints of previous designs. An interesting consequence of the proposed design is that it has an effective wavelength which asymptotically goes to infinity with frequency.

Integrated photonic guided metalens based on a pseudo-graded index distribution

Abstract: In this article, we report an integrated optical nanolens exhibiting a pseudo-graded index distribution in a guided configuration. This dielectric metalens relies on a permittivity distribution through dielectric strips of the core material, which is compatible with existing silicon photonic technology. We show in this paper that effective medium theory (EMT) inaccurately predicts the focal length of such devices, and we propose an efficient and accurate design approach based on 2D finite element method (FEM) mode calculations that are in good agreement with 3D FDTD simulations. The lens was fabricated on a 200 mm silicon on insulator pilot line, and fibre-to-fibre optical characterizations revealed an excellent transmission of 85% for TM polarization, in line with the simulated performance (90%). The proposed approach can be easily extended to width-variable strips, enabling the realization of all types of graded index devices, especially those derived from transformation optics.

General properties of surface modes in binary metal-dielectric metamaterials

Abstract: We present general properties of surface modes in binary metal-dielectric metamaterials. We show mechanism for surface mode formation and analyze their existence conditions for semi-infinite metamaterials in the frame of couple mode theory.

Singular Lenses for Flexural Waves on Elastic Thin Curved Plates

Abstract: Transformation optics, which is generically applicable to other classical waves such as acoustic and elastic waves, provides an emerging design paradigm to manipulate waves. However, some lenses and optical-transformation devices require a singular refractive index; meeting this requirement is a significant challenge. A method called transmutation can relax some types of index singularity into finite anisotropy around the singularity. Here, we show that such lenses with a singularity for flexural waves can be obtained by approaching a near-zero thickness of the plate precisely at the location of the singularity. As examples, we demonstrate a series of Eaton lenses theoretically and experimentally by projecting the refractive index in space onto the thickness in plates and by working in a broad frequency range in which impedance mismatch is negligible. This framework offers an insight into feasible methods that can be used to develop singular devices such as cloaking devices on thin flexible curved plates and can be further extended to a general methodology for shaping elastic waves. We hope that this elastic platform can also be a test bed to indirectly study unprecedented phenomena enabled by gravitational and quantum fields in terms of analog models.