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Showing papers by "John B. Pendry published in 2001"


Journal ArticleDOI
TL;DR: A fully three-dimensional theoretical study of the extraordinary transmission of light through subwavelength hole arrays in optically thick metal films shows that the enhancement of transmission is due to tunneling through surface plasmons formed on each metal-dielectric interface.
Abstract: We present a fully three-dimensional theoretical study of the extraordinary transmission of light through subwavelength hole arrays in optically thick metal films. Good agreement is obtained with experimental data. An analytical minimal model is also developed, which conclusively shows that the enhancement of transmission is due to tunneling through surface plasmons formed on each metal-dielectric interface. Different regimes of tunneling (resonant through a ``surface plasmon molecule,'' or sequential through two isolated surface plasmons) are found depending on the geometrical parameters defining the system.

1,577 citations



Journal ArticleDOI
TL;DR: In this article, it was shown that the optical transmission through subwavelength holes in metal films can be enhanced by several orders of magnitude by enabling interaction of the incident light with independent surface plasmon (SP) modes on either side of the film.

495 citations


Journal ArticleDOI
02 Feb 2001-Science
TL;DR: It is shown that a new magnetic material offers novel possibilities for guiding RF flux to the receiver coil, permitting a clear image to be obtained where none might otherwise be detectable.
Abstract: Magnetic resonance imaging and spectroscopy systems use coils, either singly or as arrays, to intercept radio-frequency (RF) magnetic flux from regions of interest, often deep within the body. Here, we show that a new magnetic material offers novel possibilities for guiding RF flux to the receiver coil, permitting a clear image to be obtained where none might otherwise be detectable. The new material contains microstructure designed according to concepts taken from the field of photonic band gap materials. In the RF range, it has a magnetic permeability that can be produced to specification while exhibiting negligible direct-current magnetism. The latter property is vital to avoid perturbing the static and audio-frequency magnetic fields needed to obtain image and spectral data. The concept offers a new paradigm for the manipulation of RF flux in all nuclear magnetic resonance systems.

454 citations


Journal ArticleDOI
TL;DR: In this paper, the speed of light in vacuum can be defined as c = 1/√0μ0, where 0 is the permittivity of free space and μ0 is the permeability.
Abstract: Electrical permittivity and magnetic permeability are concepts that are deeply embedded in electromagnetism. The electrical permittivity of a material determines its response to an applied electric field, while the permeability summarizes how it reacts to an applied magnetic field. Together the permittivity and permeability determine how the material responds to electromagnetic radiation of all wavelengths. Indeed, the speed of light in vacuum can be defined as c = 1/√0μ0, where 0 is the permittivity of free space and μ0 is the permeability.

76 citations


Patent
20 Jun 2001
TL;DR: In this paper, the singularity in the flux pattern has the result that magnetic resonant disturbances in a plane C,E normal to the line C,D are focussed into a plane D,F also normal to C, D and vice versa.
Abstract: A material having magnetic permeability at rf frequency, for example a microstructured magnetic material has a magnetic permeability of negative value but unity magnitude over a particular rf frequency range The singularity in the flux pattern has the result that magnetic resonant disturbances in a plane C,E normal to the line C,D are focussed into a plane D,F also normal to the line C,D and vice versa This is particularly applicable to magnetic resonance apparatus, since the material can be used to transfer the rf magnetic flux distribution in a target region in a patient, for example at C,E to D,F where the flux may be directly measured by receive coils Equally, transmit coils may generate flux to be focussed into the target region by the material Magnetic resonance apparatus may be constructed which does not require gradient coils, and rf hypothermia may be carried out in a focussed way, minimising damage to surrounding tissue

16 citations


Journal ArticleDOI
TL;DR: In this article, a new method to describe the emission properties of cavity structures is developed, which starts with incident radiation from a source outside the structure and records the resulting energy reaching the position of the desired source inside the cavity.
Abstract: A new method to describe the emission properties of cavity structures is developed. Rather than solving the problem directly, we start with incident radiation from a source outside the structure and record the resulting energy reaching the position of the desired source inside the cavity. Time-reversal symmetry then gives us the emissivity in the chosen direction. The implementation of the approach is very straightforward and essentially requires the calculation of the reflection and transmission properties of the structure. Example calculations of the emission properties in 1 D planar cavities are presented to verify the approach. Finally the emission from a cavity structure comprising 2D photonic crystals is calculated which shows a sigificant reduction in wasted emission away from the main cavity mode.

10 citations


Book ChapterDOI
01 Jan 2001
TL;DR: In this paper, the dielectric response of metals is dominated by the plasma-like behavior of the electron gas at optical frequencies, and the damping factor is introduced through damping factors, which in turn can be related to the conductivity of the metal.
Abstract: At optical frequencies the dielectric response of metals is dominated by the plasma like behaviour of the electron gas: $$ \varepsilon \left( \omega \right) = 1 - \frac{{\omega _p^2}}{{\omega \left( {\omega + i\gamma } \right)}}.$$ There is a characteristic plasma frequency which is the natural frequency of oscillation of the electron gas $$ \omega _p^2 = \frac{{n{e^2}}}{{{\varepsilon _0}{m_e}}}.$$ Dissipation is introduced through the damping factor, γ, which in turn can be related to the conductivity of the metal if we assume that the same form persists to low frequencies, $$ \gamma = {\sigma ^{ - 1}}{\varepsilon _0}.$$ It is customary to ignore the dependence of e on wave vector, q, and this is a good approximation for many purposes. However in some circumstances, for example where we consider the response of nanostructures to light, we may have to worry about the short wavelength, large q behaviour of e. One obvious cut-off length is the separation between electrons in the metal. Another might be the inelastic scattering length for electrons which is typically a few nanometres. The very short wavelength response of metals at optical frequencies has been studied in the electron microscope where losses at large momentum transfers can be measured.

6 citations


Proceedings ArticleDOI
11 May 2001
TL;DR: In this paper, it was shown that at the frequency where epsilon = -1 a highly conducting metal such as silver can act as a lens, refocusing electrostatic fields defined in some object plane, into an image plane some distance away.
Abstract: Summary form only given. Most metals have negative dielectric functions and their surfaces support plasma modes that couple to incident light. Focusing of surface plasma modes is not restricted by the free space wavelength offering the possibility of huge concentrations of radiative energy in very small volumes. In a recent refinement we showed that at the frequency where epsilon = -1 a highly conducting metal such as silver can act as a lens, refocusing electrostatic fields defined in some object plane, into an image plane some distance away.