Transmission of light through a periodic array of slits in a thick metallic film

The University of Arizona, Tucson, Arizona, United States
Optics Express (Impact Factor: 3.49). 07/2005; 13(12):4485-91. DOI: 10.1364/OPEX.13.004485
Source: PubMed


Finite-difference-time-domain (FDTD) computer simulations reveal interesting features of the transmission of a linearly polarized plane-wave through a periodic array of sub-wavelength slits in a thick metal film (incident E-field perpendicular to the slits' long axis). The results show that slit transmission has a quasi-periodic dependence on both the film thickness and the period of the slits. This indicates that resonant surface waves excited at the top and bottom facets of the metal film as well as resonant guided modes along the depth of the slits play major roles in determining the transmission efficiency of the array. When the slit periodicity is an integer-multiple of the surface-plasmon wavelength, transmission drops to zero regardless of film thickness; in other words, excitation of surface plasmons reduces the transmission efficiency. When the slit periodicity deviates from the aforementioned value, maximum transmission through the slits is achieved by adjusting the film thickness. In the thickness dimension, transmission maxima occur periodically, with a period of half the effective wavelength of the guided mode in each slit waveguide. Optimum transmission is thus achieved by simultaneously adjusting the film thickness and the period of the slits. Computed field profiles clarify the role played by the induced surface charges and currents in enhancing the light's coupling efficiency into and out of the slits.

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Available from: Masud Mansuripur, Aug 17, 2014
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    • "The analysis of EM/optical propagation through these PIM-NIM PBG structures, where the longitudinal refractive index changes may be significant and abrupt, requires the use of numerical techniques. There are several methods for numerically solving electromagnetic problems for any arbitrary geometry, such as the Green's function method [47], the multiple multipole technique [48], and the finite difference time domain (FDTD) technique [49], [50]. While the multiple multipole technique requires relatively little computational load, it requires a significant investment in user learning. "
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