Transformation optics

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

Optically induced metal-to-dielectric transition in Epsilon-Near-Zero metamaterials.

Abstract: Epsilon-Near-Zero materials exhibit a transition in the real part of the dielectric permittivity from positive to negative value as a function of wavelength. Here we study metal-dielectric layered metamaterials in the homogenised regime (each layer has strongly subwavelength thickness) with zero real part of the permittivity in the near-infrared region. By optically pumping the metamaterial we experimentally show that close to the Epsilon-Near-Zero (ENZ) wavelength the permittivity exhibits a marked transition from metallic (negative permittivity) to dielectric (positive permittivity) as a function of the optical power. Remarkably, this transition is linear as a function of pump power and occurs on time scales of the order of the 100 fs pump pulse that need not be tuned to a specific wavelength. The linearity of the permittivity increase allows us to express the response of the metamaterial in terms of a standard third order optical nonlinearity: this shows a clear inversion of the roles of the real and imaginary parts in crossing the ENZ wavelength, further supporting an optically induced change in the physical behaviour of the metamaterial.

Electromagnetic source transformations using superellipse equations

Abstract: Transformation optics can be used to design media with unique properties that alter the behavior of electromagnetic waves in passive space and recently in space containing source distributions. We present source transformations where current from a linear radiator is spread over a cylindrical shell with various cross sections. The semianalytic transformations are based on superellipse equations. Finite-element full-wave simulations of transformations from a dipole to a cylinder, diamond-shaped cylinder, and flattened cylinder are presented. The radiation pattern of the dipole seen by an outside observer is replicated in all cases demonstrating the potential applicability of source transformations to conformal antenna design.

Complex band structure of nanostructured metal-dielectric metamaterials.

Abstract: We study complex eigenmodes of layered metal-dielectric metamaterials. Varying losses from weak to realistic, we analyze band structure of the metamaterial and clarify effect of lossess on its intrinsic electromagnetic properties. The structure operates in a regime with infinite numbers of eigenmodes, whereas we analyze dominant ones.

Conformal carpet and grating cloaks.

Abstract: We introduce a class of conformal versions of the previously introduced quasi-conformal carpet cloak, and show how to construct such conformal cloaks for different cloak shapes. Our method provides exact refractive-index profiles in closed mathematical form for the usual carpet cloak as well as for other shapes. By analyzing their asymptotic behavior, we find that the performance of finite-size cloaks becomes much better for metal shapes with zero average value, e.g., for gratings.