![]() Epsilon-near-zero metamaterials and electromagnetic sources: tailoring the radiation phase pattern. Macroscopic invisibility cloaking of visible light. ![]() Three-dimensional invisibility cloak at optical wavelengths. Multifrequency optical invisibility cloak with layered plasmonic shells. Metamaterial electromagnetic cloak at microwave frequencies. Overcoming the diffraction limit with a planar left-handed transmission-line lens. Optical Metamaterials Fundamentals and Applications (Springer, New York, 2010). General relativity in electrical engineering. The Classical Theory Of Fields (Butterworth-Heinemann, Oxford, 1975). Now, with new abilities to construct 3D curved structures with nanometric resolution, it is intriguing to study what happens when the 3D photonic structures have features comparable to the wavelength of the light propagating within them. However, these pioneering experiments were only carried out in macroscopic systems, always in the paraxial regime, and for 3D bodies whose curvature varies slowly with respect to the wavelength. In the past few years, curved-space photonic settings have been studied in experiments with curved surface waveguides coating 3D bodies 15, 16, 17. Because these settings use traditional 2D fabrication techniques, they generally do not exploit the ability to create true curved space in 3D systems 14. This challenge has been addressed by using various methods ranging from tailoring combinations of different materials at nanoscale resolution 7 to the development of alternative plasmonic materials 13. ![]() However, the fabrication of materials with specific inhomogeneous optical properties is still a major challenge, especially for operation in the visible-light regime. These applications include, in particular, superlenses 4 and cloaking schemes 5, 6, 7, 8, the realization of which often requires negative-refractive-index metamaterials 9 and epsilon near-zero media 10, 11, 12. Starting in 2000, the rapid development of the field of metamaterials suggested emulation of GR phenomena for optical applications as one of its main routes 2, 3. However, for a long time no technology could implement GR concepts in optics. This generic concept can serve as the basis for curved nanophotonics and can be employed in integrated photonic circuits.įor decades, general relativity (GR) phenomena have provided exciting inspiration in the field of electromagnetism, as reflected in the famous statement by Landau and Lifshitz: ‘We may say that, with respect to its effect on the electromagnetic field, a static gravitational field plays the role of a medium with electric and magnetic permeabilities ε, μ’ 1. Finally, our structure exhibits tunnelling through an electromagnetic bottleneck by transforming guided modes into radiation modes and back. Our construction allows control over the trajectories, the diffraction properties and the phase and group velocities of wavepackets propagating within the curved-space structure. ![]() We demonstrate this concept by studying the evolution of light in a paraboloid structure inspired by the Schwarzschild metric describing the space surrounding a massive black hole. We present a new class of nanophotonic structures with intricate design in three dimensions inspired by general relativity concepts, where the evolution of light is controlled through the space curvature of the medium. Conventional nanophotonic structures are fabricated in planar settings, similar to electronic integrated circuits. Nanophotonics is based on the ability to construct structures with specific spatial distributions of the refractive index. ![]()
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