Study of near-zone fields of a small aperture

Abstract

The structure or the near-zone field transmitted through an electrically small aperture in a perfectly conducting plane is investigated. We dwell on two issues that are of importance to engineers analyzing small aperture problems. The first question addressed is how far should one recede from the aperture in order to justifiably use the well-known aperture dipole approximations. Alternatively, how close may a source or a backing object be located without appreciably effecting the aperture quasistatic field distributions. The second consideration is to what distance the radiation emanating from the aperture remains collimated and how strongly is the near-field intensity dependent upon distance. The model used for our calculation is that of a small circular aperture for which the quasistatic aperture field distributions are analytically derivable. It is presumed that this should give an indication of the near-zone field characteristics to be expected in the general case.

Collection-mode near-field imaging with 0.5-THz pulses

“…The latter are usually referred to as evanescent modes. The amplitude of the evanescent modes is significantly larger than that of the propagating modes (real ) at a short distance from the aperture ( ) [15]. At a distance approximately equal to the aperture size, their contribution is comparable.…”

“…The curve is normalized to the amplitude of the incident field. The calculations, based on the modal approximation [15], distinguish waves with real and imaginary wavenumbers. The wavelength of 430 m corresponds to the spectral maximum of the terahertz field measured by the probe.…”

Dressed photon technology

“…A na ï ve wave-optical picture of the optical near-fi eld has been given [11] . This picture, however, is not adequate for use as a theoretical basis for realizing qualitative innovations; to do so requires a quantum optical approach and quantum fi eld theory.…”

Complex Image Method Analysis of a Plane Wave-Excited Subwavelength Circular Aperture in a Planar Screen

“…The first numerical studies of the transmitted field distribution based on the BB aperture model were by Leviatan [9], Dürig et al [10], and Nakano and Kawata [11], using the space domain method, and by Van Labeke et al [12][13][14] and Grober et al [15], using the spectral domain approach. The latter method has the advantage that the fields may be expressed as one-dimensional integrals [2,14,15], and that planar and layered dielectric samples may be easily incorporated in the formulation [3,13,14,16].…”