6,002 research outputs found
Theory of Transmission of Light by Sub-wavelength Cylindrical Holes in Metallic Films
This paper presents theory and finite-difference time-domain (FDTD)
calculations for a single and arrays of sub-wavelength cylindrical holes in
metallic films presenting large transmission. These calculations are in
excellent agreement with experimental measurements. This effect has to be
understood in terms of the properties exhibited by the dielectric constant of
metals which cannot be treated as ideal metals for the purpose of transmission
and diffraction of light. We discuss the cases of well-differentiated metals
silver and tungsten. It is found that the effect of surface plasmons or other
surface wave excitations due to a periodical set of holes or other roughness at
the surface is marginal. The effect can enhance but also can depress the
transmission of the arrays as shown by theory and experiments. The peak
structure observed in experiments is a consequence of the interference of the
wavefronts transmitted by each hole and is determined by the surface array
period independently of the material. Without large transmission through a
single hole there is no large transmission through the array. We found that in
the case of Ag which at the discussed frequencies is a metal there are
cylindrical plasmons at the wall of the hole, as reported by Economu et al 30
years ago, that enhanced the transmission. But it turns out, as will be
explained, that for the case of W which behaves as a dielectric, there is also
a large transmission when compared with that of an ideal metal waveguide. To
deal with this problem one has to use the measured dielectric function of the
metals. We discuss thoroughly all these cases and compare with the data.Comment: 13 pages and 9 figure
The Happer's puzzle degeneracies and Yangian
We find operators distinguishing the degenerate states for the Hamiltonian
at that was given by Happer
et al to interpret the curious degeneracies of the Zeeman effect for
condensed vapor of Rb. The operators obey Yangian commutation relations.
We show that the curious degeneracies seem to verify the Yangian algebraic
structure for quantum tensor space and are consistent with the representation
theory of .Comment: 8 pages, Latex fil
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