Topic
Transformation optics
About: Transformation optics is a research topic. Over the lifetime, 2687 publications have been published within this topic receiving 102378 citations.
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TL;DR: In this paper, the design of arbitrarily shaped electromagnetic (EM) concentrators and their potential applications are studied. But the design is restricted to the case of a rectangular concentrator, which is much more efficient and easier than the existing techniques.
Abstract: We study the design of arbitrarily shaped electromagnetic (EM) concentrators and their potential applications. To obtain closed-form formulas of EM parameters for an arbitrarily shaped concentrator, we employ nonuniform rational B-spline (NURBS) to represent the geometrical boundary. Using the conformally optical transformation of NURBS surfaces, we propose the analytical design of arbitrarily shaped concentrators, which are composed of anisotropic and inhomogeneous metamaterials with closed-form constitutive tensors. The designed concentrators are numerically validated by full-wave simulations, which show perfectly directed EM behaviors. As one of the potential applications, we demonstrate a way to amplify plane waves using a rectangular concentrator, which is much more efficient and easier than the existing techniques. Using NURBS expands the generality of the transformation optics and could lead toward making a very general tool that would interface with commercial softwares such as 3D STUDIOMAX and MAYA.
174 citations
TL;DR: In this article, a micromachined reconfigurable metamaterial is presented, whose unit cell consists of a pair of asymmetric split-ring resonators (ASRRs); one is fixed to the substrate while the other is patterned on a movable frame.
Abstract: A micromachined reconfigurable metamaterial is presented, whose unit cell consists of a pair of asymmetric split-ring resonators (ASRRs); one is fixed to the substrate while the other is patterned on a movable frame. The reconfigurable metamaterial and the supporting structures (e.g., microactuators, anchors, supporting frames, etc.) are fabricated on a silicon-on-insulator wafer using deep reactive-ion etching (DRIE). By adjusting the distance between the two ASRRs, the strength of dipole–dipole coupling can be tuned continuously using the micromachined actuators and this enables tailoring of the electromagnetic response. The reconfiguration of unit cells endows the micromachined reconfigurable metamaterials with unique merits such as electromagnetic response under normal incidence and wide tuning of resonant frequency (measured as 31% and 22% for transverse electric polarization and transverse magnetic polarization, respectively). The reconfiguration could also allow switching between the polarization-dependent and polarization-independent states. With these features, the micromachined reconfigurable metamaterials may find potential applications in transformation optics devices, sensors, intelligent detectors, tunable frequency-selective surfaces, and spectral filters.
173 citations
TL;DR: This work considers practical phonon-polaritonic metamaterials for thermal engineering in the mid-infrared range and shows that the effect exists in spite of the losses, absorption and finite unit cell size.
Abstract: We explore the near-field radiative thermal energy transfer properties of hyperbolic metamaterials. The presence of unique electromagnetic states in a broad bandwidth leads to super-planckian thermal energy transfer between metamaterials separated by a nano-gap. We consider practical phonon-polaritonic metamaterials for thermal engineering in the mid-infrared range and show that the effect exists in spite of the losses, absorption and finite unit cell size. For thermophotovoltaic energy conversion applications requiring energy transfer in the near-infrared range we introduce high temperature hyperbolic metamaterials based on plasmonic materials with a high melting point. Our work paves the way for practical high temperature radiative thermal energy transfer applications of hyperbolic metamaterials.
170 citations
TL;DR: In this article, an invisibility carpet cloak was designed using quasi conformal mapping and fabricated in a silicon nitride waveguide on a specially developed nanoporous silicon oxide substrate with a very low refractive index (n < 1.25).
Abstract: We report an invisibility carpet cloak device, which is capable of making an object undetectable by visible light. The cloak is designed using quasi conformal mapping and is fabricated in a silicon nitride waveguide on a specially developed nanoporous silicon oxide substrate with a very low refractive index (n<1.25). The spatial index variation is realized by etching holes of various sizes in the nitride layer at deep subwavelength scale creating a local effective medium index. The fabricated device demonstrates wideband invisibility throughout the visible spectrum with low loss. This silicon nitride on low index substrate can also be a general scheme for implementation of transformation optical devices at visible frequencies.
164 citations
TL;DR: An imaging system capable of magnification, subwavelength-resolution and impedance matching, which minimizes reflection losses is developed, which is based on available materials and existing fabrication technologies.
Abstract: We propose an approach to optical imaging beyond the diffraction limit, based on transformation optics in concentric circular cylinder domains. The resulting systems allow image magnification and minimize reflection losses due to the impedance matching at the input or output boundaries. While perfect impedance matching at both surfaces can be obtained only in a system with radius-dependent magnetic permeability, we demonstrate that comparable performance can be achieved in an optimized nonmagnetic design.
164 citations