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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, the authors studied the thermal emission of highly doped silicon surfaces and showed that by modifying the doping, they can tune the frequency of emission, which can be used to realize a spatially partially coherent thermal source and a quasi-isotropic source.
77 citations
TL;DR: In this article, the authors derived a general expression for the signal in scanning near-field optical microscopy, based on the reciprocity theorem of electromagnetism, which is an overlapping integral between the local electric field and a function that characterizes the tip.
Abstract: We derive a general expression for the signal in scanning near-field optical microscopy. This expression, based on the reciprocity theorem of electromagnetism, is an overlapping integral between the local electric field and a function that characterizes the tip. In particular, it includes the dependence on wavelength, illumination conditions, and polarization. To illustrate the potentiality of this theory, we discuss the polarization behavior and the spectral response of the apertureless setup.
77 citations
TL;DR: In this article, the rotational symmetry breaking of the scalar Greens function was studied from a source point of view, and a suitable mathematical machinery for dealing with the symmetry breaking procedure from the source point-of-view was developed in detail.
Abstract: We continue in this paper a comprehensive theory of antenna near fields inaugurated in Part I. The concept of near-field streamlines is introduced using the Weyl expansion in which the total field is decomposed into propagating and nonpropagating parts. This process involves a breaking of the rotational symmetry of the scalar Greens function that originally facilitated the derivation of the Weyl expansion. Such symmetry breaking is taken here to represent a key to understanding the structure of the near fields and how antennas work in general. A suitable mathematical machinery for dealing with the symmetry breaking procedure from the source point of view is developed in detail, and the final results are expressed in clear and compact form susceptible to direct interpretation. We then investigate the concept of energy in the near field where the localized energy (especially the radial localized energy) and the stored energy are singled out as the most important types of energy processes in the near-field zone of general antenna systems. A new devolvement is subsequently undertaken by generalizing the Weyl expansion in order to analyze the structure of the near field, but this time from the far-field point of view. A hybrid series combining the Weyl and Wilcox expansions is derived, after which only the radial streamline picture turns out to be compatible with the far-field description via Wilcox series. We end up with an explication of the general mechanism of far-field formation from the source point of view. It is found that the main formative processes in the antenna near-field zone are reducible to simple geometrical and filtering operations.
77 citations
TL;DR: The physical pictures of Laguerre-Gaussian beams are well illustrated from the vectorial structure, which may provide a new approach to manipulate laser beams.
Abstract: Based on the vector angular spectrum of the electromagnetic beam and the method of stationary phase, the analytical vectorial structure of the Laguerre-Gaussian beam has been presented in the far field. According to the analytical electromagnetic representations of the TE and TM terms, the energy flux distributions of the TE term, the TM term, and the whole beam are investigated in the far field, respectively. The formulas obtained are applicable not only to the paraxial case, but also to the nonparaxial case. The physical pictures of Laguerre-Gaussian beams are well illustrated from the vectorial structure, which may provide a new approach to manipulate laser beams.
77 citations
16 Aug 2000
TL;DR: In this article, the authors focused on the calculations of intensity distributions as a function of typical parameters in laser cleaning, and examined the effects of the optical resonance within the transparent particle with size a approximately (lambda) (radiation wavelength) on the intensity distribution in the contacted area (substrate surface).
Abstract: The optical resonance within the transparent particle with size a approximately (lambda) (radiation wavelength) strongly influences the intensity distribution in the contacted area (substrate surface). As a result, the efficiency of dry laser cleaning is a strong non-monotonous function of the particle size. Another important effect is related to the interaction between scattered and reflected light of the particle on the surface (near-field effect). Examination of these effects is done within the frame of exact solution of the light scattering problem. The distribution of absorbed intensity is the basic input characteristic for the laser cleaning model. It is used during solution of heat equation and equations of theory of the elasticity (thermal expansion and acoustic wave generation). This paper concentrates on the calculations of intensity distributions as a function of typical parameters in laser cleaning.
77 citations