Diffraction Focusing of Electromagnetic Radiation by Transmission through Sub-Wavelength Nanoapertures

Diffraction of a Plane Electromagnetic Wave by a Circular Aperture in a Conducting Screen of Finite Thickness

“…A(α) and Ā(α) are not yet determined amplitudes of these modes, and the coefficients i/k 2 and i/(k 2 β) are extracted from the integrands in order to simplify the following formulas. For the same purpose, expressions for incident (6) and reflected plane waves in the given region are specially distinguished in (13a).…”

“…The classical problem of electromagnetic wave diffraction by a slot or a circular aperture in a conducting screen is of great interest in the context of the recent discovery of two interesting phenomena: the occurrence of an anomalously high local intensity of the transmitted radiation [1][2][3] and the appearance of lensless focusing of the diffraction slot image, when the effective width of this image turns out to be several times smaller than the transverse dimensions of the aperture [4,5]. An effective theoretical method for searching the region of existence of the latter effect was proposed in [6,7] † . It is obvious that these two phenomena are interconnected, since a high local intensity of the field can take place when it is concentrated in a small region, and these phenomena are noticeably manifested only for microapertures in the near zone, when the aperture dimensions, the screen thickness, and the distance from it to the plane of the diffraction pattern observation have dimensions on the order of one to several wavelengths of radiation.…”