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Near and far field
About: Near and far field is a research topic. Over the lifetime, 15922 publications have been published within this topic receiving 220571 citations.
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TL;DR: In this paper, a generalization to three dimensions of the discrete wave number representation method was presented to study the near field of a 3D seismic source embedded in a layered medium, where elastic wave fields are represented by a superposition of plane waves propagating in discrete directions.
Abstract: We present the generalization to three dimensions of the discrete wave number representation method of Bouchon and Aki (1977). The method is developed to study the near field of a three-dimensional seismic source embedded in a layered medium. The elastic wave fields are represented by a superposition of plane waves propagating in discrete directions. The discretization is exact and results from a periodic two-dimensional arrangement of sources. The accuracy of the method is checked, in the case of a rectangular dislocation source radiating in an infinite medium, by comparing the results obtained with Madariaga's (1978) exact solution. Examples of the calculation of strong ground motion produced by a thrust fault and a strike slip fault are presented.
280 citations
TL;DR: In this article, the angular distribution of light emitted by an atomic system, e.g., a fluorescent molecule, located in a dielectric medium 1 at distance z 0 from the interface to a different dielectrous medium 2, was derived.
Abstract: We have derived analytic expressions for the angular distribution of light emitted by an atomic system, e.g., a fluorescent molecule, located in a dielectric medium 1 at distance z0 from the interface to a different dielectric medium 2. The theory is rigorously valid for electric and magnetic dipole transitions with arbitrary orientation of the dipole transition moment. (In Paper II [ J. Opt. Soc. Am.57, 1615– 1619 ( 1977)], only the special case of dipoles oriented perpendicular to the interface had been treated.) The radiation patterns of dipoles located on the interface (z0 = 0) and oriented parallel to it, and ensembles of such dipoles radiating incoherently with randomly oriented dipole moments were examined in particular. They differ greatly from the corresponding well-known dipole radiation patterns in an unbounded medium 1, due to the wide-angle interferences of emitted plane waves, and radiation from evanescent waves in the dipole’s near field into medium 2, if this is denser than medium 1.
279 citations
Patent•
21 Dec 2007TL;DR: A dielectric polyrod has at least one tapered section, where a section exposed outside of the waveguide is tapered a long a curve that depends on the Dielectric constant of the material used.
Abstract: A dielectric polyrod having at least one tapered section, where a section exposed outside of the waveguide is tapered a long a curve that depends on the dielectric constant of the material used. The invention also relates to an aperture matched polyrod antenna which includes the same and an inductive tuning element used to achieve wideband impedance match and to create a Gaussian beam in the radiating near field of the antenna, suitable to mimic a small region plane wave.
278 citations
TL;DR: A novel light-emitting probe for scanning near-field optical microscopy is investigated theoretically and the three-dimensional vectorial Helmholtz equation is solved for the new probe geometry by using the multiple multipole method.
Abstract: A novel light-emitting probe for scanning near-field optical microscopy is investigated theoretically. The three-dimensional vectorial Helmholtz equation is solved for the new probe geometry by using the multiple multipole method. The novel probe consists of a dielectric tip that is entirely metal coated. It provides a single near-field spot that can be smaller than 20 nm (FWHM). The dependence on tip radius, taper angle, and metal thickness in front of the tip is investigated for the power transmission through the probe as well as for the spot size.
277 citations
TL;DR: In this article, it was shown that far-field polarization microscopy can yield the 3D orientation of certain highly symmetric single chromophores (CdSe nanocrystal quantum dots in the present case).
Abstract: A complete understanding of any complex molecular system generally requires a knowledge of the three-dimensional (3D) orientation of its components relative both to each other, and to directional perturbations such as interfaces and electromagnetic fields. Far-field polarization microscopy is a convenient and widespread technique for detecting and measuring the orientation of single chromophores. But because the polarized electromagnetic field that is used to probe the system lacks a significant longitudinal component, it was thought that, in general, only 2D orientation information could be obtained1,2,3. Here we demonstrate that far-field polarization microscopy can yield the 3D orientation of certain highly symmetric single chromophores (CdSe nanocrystal quantum dots in the present case). The key requirement is that the chromophores must have a degenerate transition dipole oriented isotropically in two dimensions, which gives rise to a perpendicular ‘dark axis’ that does not couple to the light field. By measuring the fluorescence intensity from the dipole as a function of polarization angle, it is possible to calculate both the tilt angle between the dark axis and the sample plane, as well as the in-plane orientation, and hence obtain the 3D orientation of the chromophore
276 citations