Costas M. Soukoulis

Determination of effective permittivity and permeability of metamaterials from reflection and transmission coefficients

We analyze the reflection and transmission coefficients calculated from transfer matrix simulations on finite lengths of electromagnetic metamaterials, to determine the effective permittivity ~«! and permeability ~m! .W e perform this analysis on structures composed of periodic arrangements of wires, split ring resonators ~SRRs!, and both wires and SRRs. We find the recovered frequency-dependent« and m are entirely consistent with analytic expressions predicted by effective medium arguments. Of particular relevance are that a wire medium exhibits a frequency region in which the real part of « is negative, and SRRs produce a frequency region in which the real part of m is negative. In the combination structure, at frequencies where both the recovered real parts of « and m are simultaneously negative, the real part of the index of refraction is also found to be unambiguously negative.

Past achievements and future challenges in the development of three-dimensional photonic metamaterials

Photonic metamaterials are man-made structures composed of tailored micro- or nanostructured metallo-dielectric sub-wavelength building blocks that are densely packed into an effective material. This deceptively simple, yet powerful, truly revolutionary concept allows for achieving novel, unusual, and sometimes even unheard-of optical properties, such as magnetism at optical frequencies, negative refractive indices, large positive refractive indices, zero reflection via impedance matching, perfect absorption, giant circular dichroism, or enhanced nonlinear optical properties. Possible applications of metamaterials comprise ultrahigh-resolution imaging systems, compact polarization optics, and cloaking devices. This review describes the experimental progress recently made fabricating three-dimensional metamaterial structures and discusses some remaining future challenges.

Magnetic Metamaterials at Telecommunication and Visible Frequencies

Arrays of gold split rings with a 50-nm minimum feature size and with an LC resonance at 200 THz frequency (1.5 microm wavelength) are fabricated. For normal-incidence conditions, they exhibit a pronounced fundamental magnetic mode, arising from a coupling via the electric component of the incident light. For oblique incidence, a coupling via the magnetic component is demonstrated as well. Moreover, we identify a novel higher-order magnetic resonance at around 370 THz (800 nm wavelength) that evolves out of the Mie resonance for oblique incidence. Comparison with theory delivers good agreement and also shows that the structures allow for a negative magnetic permeability.

Negative-index metamaterial at 780 nm wavelength.

We further miniaturize a recently established silver-based negative-index metamaterial design. By comparing transmittance, reflectance, and phase-sensitive time-of-flight experiments with theory, we infer a real part of the refractive index of -0.6 at a 780 nm wavelength--which is visible in the laboratory.

Photonic band gaps in three dimensions: New layer-by-layer periodic structures

Abstract A new three-dimensional (3D) periodic dielectric structure constructed with layers of dielectric rods of circular, elliptical, or rectangular shape is introduced. This new structure possesses a full photonic band gap of appreciable frequency width. At midgap, an attenuation of 21 dB per unit cell is obtained. This gap remains open for refractive indices n ≥ 1.9. Furthermore, this new 3D layer structure potentially has the additional advantage that it can be easily fabricated using conventional microfabrication techniques on the scale of optical wavelengths.

Metamaterial with negative index due to chirality

Artificial magnetism, negative permeability and negative refractive index are demonstrated in 3D-chiral metamaterial that shows giant polarization rotation and circular dichroism. ∗ As presented at the Quantum Electronics and Laser Sciences Conference (CLEO/QELS 2008), San Jose, CA, USA, 5 May 2008, paper QMA4.

Low-loss negative-index metamaterial at telecommunication wavelengths

We fabricate and characterize a low-loss silver-based negative-index metamaterial based on the design of a recent theoretical proposal. Comparing the measured transmittance and reflectance spectra with theory reveals good agreement. We retrieve a real part of the refractive index of Re(n)= -2 around 1.5 microm wavelength. The maximum of the ratio of the real to the imaginary part of the refractive index is about three at a spectral position where Re(n)= -1. To the best of our knowledge, this is the best figure of merit reported for any negative-index photonic metamaterial to date.

Low-loss metamaterials based on classical electromagnetically induced transparency

We demonstrate theoretically that electromagnetically induced transparency can be achieved in metamaterials, in which electromagnetic radiation is interacting resonantly with mesoscopic oscillators rather than with atoms. We describe novel metamaterial designs that can support a full dark resonant state upon interaction with an electromagnetic beam and we present results of its frequency-dependent effective permeability and permittivity. These results, showing a transparency window with extremely low absorption and strong dispersion, are confirmed by accurate simulations of the electromagnetic field propagation in the metamaterial.

Cut-wire pairs and plate pairs as magnetic atoms for optical metamaterials.

We study the optical properties of metamaterials made from cut-wire pairs or plate pairs. We obtain a more pronounced optical response for arrays of plate pairs, a geometry that also eliminates the undesirable polarization anisotropy of the cut-wire pairs. The measured optical spectra agree with simulations, revealing negative magnetic permeability in the range of telecommunications wavelengths. Thus nanoscopic plate pairs might serve as an alternative to the established split-ring resonator design.

Photonic band gaps and localization

Localization, Diffusion, and Correlation: The Localization of Light S. John. The Speed of Diffusing Light B.A. van Tiggelen, A. Lagendijk. Diffusion of Classical Waves in Random Media C.M. Soukoulis, et al. Accurate Measurement of Backscattered Light from Random Media P.N. den Outer, et al. Photonic Band Gaps: Photonic Band Structure E. Yablonovitch. Photonic Gaps for Electromagnetic Waves in Periodic Dielectric Structures K.M. Ho, et al. Plane-Wave Calculation of Photonic Band Structure K.M. Leung. Measurements of Localization and Photonic Band Gap Systems in Two Dimensions S. Schultz, D.R. Smith. Wave Propagation in Random Media: Localization Transition in Anisotropic and Inhomogenous Systems P. Sheng, Z.Q. Zhang. Statistical Inversion of Stratified Media from Acoustic Pulses Scattered at Two Angles of Incidence B. White, et al. 30 additional articles. Index.