Showing papers by "John B. Pendry published in 2005"

Surfaces with holes in them: new plasmonic metamaterials

Abstract: In this paper we explore the existence of surface electromagnetic modes in corrugated surfaces of perfect conductors. We analyse two cases: one-dimensional arrays of grooves and two-dimensional arrays of holes. In both cases we find that these structures support surface bound states and that the dispersions of these modes have strong similarities with the dispersion of the surface plasmon polariton bands of real metals. Importantly, the dispersion relation of these surface states is mainly dictated by the geometry of the grooves or holes and these results open the possibility of tailoring the properties of these modes by just tuning the geometrical parameters of the surface.

Saturation of the Magnetic Response of Split-Ring Resonators at Optical Frequencies

Abstract: We investigate numerically the limits of the resonant magnetic response with a negative effective permeabilityeff for single-ring multicut split-ring resonator (SRR) designs up to optical frequencies We find the breakdown of linear scaling due to the free electron kinetic energy for frequencies above � 100 THz Above the linear scaling regime, the resonance frequency saturates, while the amplitude of the resonant permeability decreases, ultimately ceasing to reach negative value The highest resonance frequency at whicheff < 0 increases with the number of cuts in the SRR A LC circuit model provides explanation of the numerical data

Perfect corner reflector.

Abstract: We numerically investigate the electromagnetic field radiated by a line source within a perfect lens [Phys. Rev. Lett. 85, 3966 (2000)] consisting of two orthogonal planes delimiting positive and negative index media. Use of a coordinate transformation [J. Phys. Condens Matter 15, 6345 (2003)] together with a well-adapted transfer-matrix method permits rigorous calculation of the vector field. We find that two negative corners combine to make a cavity that traps light along closed trajectories. Finally, we numerically show that the field presents some spatial oscillations with a period that is proportional to absorption sigma inside the negative materials as 1/ln sigma and that it is associated with an infinite density of states when sigma tends toward 0.

Generating Bessel beams by use of localized modes.

Abstract: We propose a novel method for generating both propagating and evanescent Bessel beams. To generate propagating Bessel beams we propose using a pair of distributed Bragg reflectors (DBRs) with a resonant point source on one side of the system. Those modes that couple with the localized modes supported by the DBR system will be selectively transmitted. This is used to produce a single narrow band of transmission in κ space that, combined with the circular symmetry of the system, yields a propagating Bessel beam. We present numerical simulations showing that a propagating Bessel beam with central spot size of ∼0.5λ0 can be maintained for a distance in excess of 3000λ0. To generate evanescent Bessel beams we propose using transmission of a resonant point source through a thin film. A transmission resonance is produced as a result of the multiple scattering occurring between the interfaces. This narrow resonance combined with the circular symmetry of the system corresponds to an evanescent Bessel beam. Because propagating modes are also transmitted, although the evanescent transmission resonance is many orders of magnitude greater than the transmission for the propagating modes, within a certain distance the propagating modes swamp the exponentially decaying evanescent ones. Thus there is only a certain regime in which evanescent Bessel beams dominate. However, within this regime the central spot size of the beam can be made significantly smaller than the wavelength of light used. Thus evanescent Bessel beams may have technical application, in high-density recording for example. We present numerical simulations showing that with a simple glass thin film an evanescent Bessel beam with central spot size of ∼0.34λ0 can be maintained for a distance of 0.14λ0. By choice of different material parameters, the central spot size can be made smaller still.

Electromagnetic response of a point-dipole crystal

Abstract: We study the electromagnetic response of a cubic array of polarizable and resonant point dipoles. We show, that in addition to the formation of photonic and polaritonic bands and gaps in the dispersion of transverse waves, the array allows for bulk and surface plasmon wave propagation, as well as negative refraction in a polaritonic band, and subwavelength lensing. We suggest experimental arrangements for demonstration of these effects, both at microwave and optical frequencies.

Infrared spectroscopy and ellipsometry of magnetic metamaterials

Abstract: We present S and P polarized measurements of artificial bianisotropic magnetic metamaterials with resonant behavior at infrared frequencies. These metamaterials consist of an array of micron sized (~40μm) copper rings fabricated upon a quartz substrate. Simulation of the reflectance is obtained through a combination of electromagnetic eigenmode simulation and Jones matrix analysis, and we find excellent agreement with the experimental data. It is shown that although the artificial magnetic materials do indeed exhibit a magnetic response, care must be taken to avoid an undesirable electric dipole resonance, due to lack of reflection symmetry in one orientation. The effects of bianisotropy on negative index are detailed and shown to be beneficial for certain configurations of the material parameters.