Showing papers by "Sheldon Schultz published in 2000"

Composite Medium with Simultaneously Negative Permeability and Permittivity

Abstract: We demonstrate a composite medium, based on a periodic array of interspaced conducting nonmagnetic split ring resonators and continuous wires, that exhibits a frequency region in the microwave regime with

Direct calculation of permeability and permittivity for a left-handed metamaterial

Abstract: Recently, an electromagnetic metamaterial was fabricated and demonstrated to exhibit a “left-handed” (LH) propagation band at microwave frequencies. A LH metamaterial is one characterized by material constants—the permeability and permittivity—which are simultaneously negative, a situation never observed in naturally occurring materials or composites. While the presence of the propagation band was shown to be an inherent demonstration of left handedness, actual numerical values for the material constants were not obtained. In the present work, using appropriate averages to define the macroscopic fields, we extract quantitative values for the effective permeability and permittivity from finite-difference simulations using three different approaches.

Spectral response of plasmon resonant nanoparticles with a non-regular shape

Abstract: We study the plasmon resonances of 10–100(nm) two-dimensional metal particles with a non-regular shape. Movies illustrate the spectral response of such particles in the optical range. Contrary to particles with a simple shape (cylinder, ellipse) non-regular particles exhibit many distinct resonances over a large spectral range. At resonance frequencies, extremely large enhancements of the electromagnetic fields occur near the surface of the particle, with amplitudes several hundred-fold that of the incident field. Implications of these strong and localized fields for nano-optics and surface enhanced Raman scattering (SERS) are also discussed.

Field polarization and polarization charge distributions in plasmon resonant nanoparticles

Abstract: We study the plasmon resonances for small two-dimensional silver particles (nanowires) with elliptical or triangular shapes in the 20 nm size range. While the elliptical particle has only two resonances, a well known fact, we demonstrate that the triangular particle displays a much more complex behaviour with several resonances over a broad wavelength range. Using animations of the field amplitude and field polarization, we investigate the properties of these different resonances. The field distribution associated with each plasmon resonance can be related to the polarization charges on the surface of the particles. Implications for the design of plasmon resonant structures with specific properties, for example, for nano-optics or surface enhanced Raman scattering are discussed.

Negative permeability from split ring resonator arrays

Abstract: Summary form only The range of values observed for the magnetic permeability, /spl mu/(/spl omega/), appears to be more restricted than the values observed for the electric permittivity, /spl epsi/(/spl omega/), where very large, and even negative values are observed This is in part due to the simple fact that there are no magnetic monopoles to provide the analogous response to that of electrons In particular, as one moves away from zero frequency, the magnitude of the magnetic response from most materials, or /spl mu/(/spl omega/), decreases rapidly, and has never been observed to take negative values While the general lack of magnetic response is observed to be the case, Maxwell's equations do not preclude a material having a large /spl mu/(/spl omega/), either positive or negative The essential requirement on the material constants appears only to be d/d and d/d for frequency-dependent materials Pendry et al (1999) have introduced conducting nonmagnetic split ring resonators (SRRs), and predicted that periodic arrays of SRRs can have a resonantly enhanced effective permeability displaying frequency regions with large positive or negative values Combining numerous SRRs into a lattice forms an effective medium, for which there exists a band of frequencies where the effective permeability is negative The SRR medium offers the possibility of engineering materials to respond to time-varying magnetic fields as well as time-varying electric fields Combining such composite media with standard materials offers the potential to yield novel and advantageous electromagnetic devices