Transmission of light through slit apertures in metallic films

The University of Arizona, Tucson, Arizona, United States
Optics Express (Impact Factor: 3.49). 01/2005; 12(25):6106-21. DOI: 10.1364/OPEX.12.006106
Source: PubMed


Transmission of polarized light through sub-wavelength slit apertures is studied based on the electromagnetic field distributions obtained in computer simulations. The results show the existence of a cutoff for E|| and a strong transmission (with no cutoff) for E?; here || and ? refer to the direction of the incident E-field relative to the long axis of the slit. These observations are explained by the standard waveguide theory involving inhomogeneous plane waves that bounce back and forth between the interior walls of the slit aperture. We examine the roles played by the slit-width, by the film thickness, and by the real and imaginary parts of the host material's dielectric constant in determining the transmission efficiency. We also show that the slit's sharp edges can be rounded to eliminate highly-localized electric dipoles without significantly affecting the slit's throughput. Finally, interference among the surface charges and currents induced in the vicinity of two adjacent slits is shown to result in enhanced transmission through both slits when the slits are separated by about one half of one wavelength.

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    • "The weaker electric field intensities inside the slit and Au/Si interface were also observed under nonresonance conditions, as shown in Fig. 1(d) and (f). These results indicate that the slit functions as a resonator of the SPP mode [21], [22], and that the high intensity SPP mode at the Au/Si interface is excited under resonance conditions. "
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    • "Both the film and the nanostrips are made of silver with relative permittivity ε m = -48.8 + i3.16 according to Ref. [11]. The wavelength of the surface plasmon wave on the metal-air interface is usually estimated by formula λ sp "
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    • "Theoretical and experimental work from several groups now seem to converge on the idea that SPs do play a central role in enhancing the transmission [30]. Similar enhanced transmission effects were also intensely studied for isolated subwavelength slits or slit arrays, showing that the transmission efficiency normalized by the slit area can be well over 100 % [31]. Figure 1a shows a sample nanohole array fabricated on a gold film on a glass slide (refer to section 3 for fabrication details). "
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