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Long wavelength Near Field Microscopy

principles. physical. Amplitude field. Evanescent term. Distance from the waveguide horizontal plane 0.22mm. The detection of evanescent fields. makes possible beating the. Abbe. diffraction limit. , which states that in. diffraction limit. optics it’s impossible to get a. subwaveleng.

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Long wavelength Near Field Microscopy

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  1. principles physical Amplitude field Evanescent term Distance from the waveguide horizontal plane 0.22mm The detection of evanescent fields makes possible beating the Abbe diffraction limit , which states that in diffraction limit optics it’s impossible to get a subwaveleng th resolution. This subwaveleng th resolution. detection is based on the optical frustration principle : onto a prism the frustration principle l l d << d << total internal reflection can be avoided if a second prism is brought very near to the first one.This phenomenon is called optical tunnel effect : on the surface of optical tunnel effect the first prism exists an evanescent field; if a suitable dielectric material is immersed in it, this one will be converted into a propagating field in order to respect the continuity conditions at the interface. A general structure of such non-propagating fields is this one Propagation term Time dependence Z (mm) Y (mm) Z (mm) X (mm) Physical principles, mathematical treatment and realization of a new near field microscope in the THz region(1011-1013 Hz) D.Coniglio, A.Doria ENEA, FIS-ACC via Enrico Fermi 45, 00044 Frascati (Rome) ITALY Visible-Infrared near field microscopy Long wavelength Near Field Microscopy Waveguide with a localised source Subwavelength aperture: Bethe’s theory Equivalent principles Equivalent electric and magnetic dipoles Dipoles’ electromagnetic field: stored energy Stored energy and electromagnetic field produced by both the dipole Fields Energy Wavelenght 2.6mm Hole radius 0.13mm (l\20) Waveguide dimensions 1mm-4mm Waveguide fundamental mode TE 10 Electromagnetic fields in tapered metallic waveguide Results References H.A.Bethe, Theory of diffraction by small holes Phy. Rev. Vol. 66, pp 163-182, 1944 Collin, Foundation for microwave engennering. S.A.Shelkunoff, Field equivalence Theorems, Comm. On Pure and Appl. Math, vol.4 pp. 43-59, 1951 Electromagnetic Field in the cutoff regime of tapered metallic waveguides. B.Knoll,F.Keilmann. Opt. Comm. 162

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