Near-field region

Near-field region, when distance is of order of magnitude of photon dimensions, R ry. 

As noted in Eq. (124), the condition is valid FAPP in the far field. However, in the inner and the near-field regions, fields E, B are not orthogonal, except along the z-axis. 

Chubar, O. and Elleaume, P. (1998) Accurate and efficient computation of synchrotron radiation in the near field region, Proceedings of the EPAC98 Conference, 22-26 June, pp. 1177-9. 

In general, the plume flow field is divided into the near-field, transition, and far-field regions [5]. The near-field region which is shown in Fig. 29.1 consists of a nearly inviscid jet core dominated by strong wave structures and a thin... 

It is common to call tvp the beam-waist radius. In the literature one often finds the phrase at the beam waist, which refers to that value of z for which the function u has its minimum radial extent. For u defined by (8), this occurs at z = 0. The distance Zp is called the confocal distance. When z < Zp we say that the Gaussian beam is in the near field. When z > Zp, the Gaussian beam is in the far field. The majority of this chapter is concerned with the behavior of u in the range 0 < z < Zp, the near-field region. The phase and amplitude of m is a complicated function of position in the near field. When z Zp and p z or when we are in the far field and the paraxial approximation is valid, it is straightforward to show that the asymptotic behavior of u approaches a diverging spherical wave from a point source at z = 0. 

In the application of high-resolution imaging based on the near-field recording technique, it is interesting to observe various light properties such as polarization, absorption spectrum, fluorescence, and so forth, in near-field regions with the combination of functionalized films for the measurement of these properties. The system has the potential of being an application of the material science of thin films. 

Hamann et al. were among the first to use the apertureless near-field approach to greatly enhance optical processes in the near-field region. One important result of this investigation is that the spatial resolution of this approach is correlated with the radius of the tip apex, while the high cross section arises from an anteima enhancement provided by the tip volume [118]. This illustrates the high potential of this approach for local spectroscopy and optical imaging on the nanometer scale. 

Higher resolution can be achieved this is because in this design the solid immersion mechanism contributes to the resolution enhancement, as the working wavelength in the near-field region is scaled down by a factor of n (refractive index of solid immersion material). As shown... 

If near-field is to be used as a measurement tool for intrinsic fluorescence properties, then one needs to know the operating conditions or samples that are appropriate for lifetime and/or spectroscopic measurements. To address this question, the FDTD method was used to compute the spectral shift and fluorescence lifetime as a function of the tip-sample gap with the molecule directly under the center of the aperture. Fig. 18 shows these results. For a yg of about 3 x 10 /s, the frequency can red shift by about 10 GHz for distances less than 50 nm. This frequency shift is not important at room temperature where the vibronic bands are approximately 10 GHz wide. At low temperatures, the linewidths are in the 0.01 to 10 GHz range, and probe-induced frequency shifts should be measurable. The frequency dependence on distance was not calculated at the larger distances, 200-400 nm, relevant to the experiment of Moerner et al. [11] (Section 2.4.2). On the other hand, the fluorescence lifetime of high quantum yield molecules was predicted to be affected in first order throughout the near-field region. Bian et al. [25] point out that for systems with fast non-radiative decay channels, the perturbations by the probe may not be significant. 

Radiating near-field region. This region is characterized by the predictable distribution of the radiating field. In the near-held region, the relative angular distribution of the held is dependent on the distance from the antenna. 

The near-field region is modeled by conventional finite elements (Zienkiewicz et al. 1999). Discretized equations of motion can be obtained using the Galerkin method. 

The earthquake response, as a direct time-domain representation, of the cylindrical liquid storage tank installed in the water-saturated transversely isotropic soil strata can be obtained by employing the numerical models of the cyHndrical tank structure, the stored liquid, the near-field region of the ground, and the transmitting boundary. The equations of motion for the tank structure, the stored Hquid, and the near-field region of the ground can be written in the time domain as follows ... 

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