Article

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: 3.53). 07/2005; 13(12):4485-91. DOI: 10.1364/OPEX.13.004485
Source: PubMed

ABSTRACT 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.

Full-text

Available from: Masud Mansuripur, Aug 17, 2014
1 Follower
 · 
78 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Phase resonances in transmission compound structures with subwavelength slits produce sharp dips in the transmission response. For all equal slits, the wavelengths of these sharp transmission minima can be varied by changing the width or the length of all the slits. In this paper we show that the width of the dip, i.e., the frequency range of minimum transmittance, can be controlled by making at least one slit different from the rest within a compound unit cell. In particular, we investigate the effect that a change in the dielectric filling, or in the length of a single slit, produces in the transmission response. We also analyze the scan angle behavior of these structures by means of band diagrams and compare them with previous results for all-equal slit structures.
    Physical Review E 08/2007; 76(1 Pt 2):016604. DOI:10.1103/PhysRevE.76.016604 · 2.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Sub-wavelength metallic tapered gratings with different-shaped slit walls are proposed in this research report. The transmission properties of the gratings have been investigated by finite difference time domain (FDTD) method. The simulation indicates that the transmission spectra strongly depend on the shapes of the slit walls. For TM-polarized light with normal incidence, the transmission coefficient and the bandwidth in the tapered gratings with the concave-parabolic slit walls are larger compared with the gratings with the convex-parabolic walls. For TE polarized light with normal incidence, the simulated results are reverse. In the visible range, the valley positions or peak positions of the transmission spectra are almost unchanged for all the gratings with different-shaped slit walls. The interaction of the electromagnetic (EM) waves on the slit walls with impendence match model has also been proposed in this paper.
    03/2014; 44(1):20-25. DOI:10.1007/s12596-014-0228-3
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In recent years, multilayer photonic bandgap structures comprising stacks of alternating layers of positive and negative index have been proposed for a variety of applications, such as perfect imaging, filters, sensors, coatings for tailored emittance, absorptance, etc. Following a brief review of the history of negative index materials, the performance of such stacks is reviewed, with emphasis on analysis of plane wave and beam propagation, and possible applications in sensing. First, the use of the transfer matrix method to analyze plane wave propagation in such structures to determine the transmittance and reflectance is developed. Examples of cases where the Bragg bandgap and the so-called zero < (n ) > gap can be used for possible applications in sensing are illustrated. Next, the transfer matrix approach is extended to simulate the spatial evolution of a collection of propagating and nonpropagating TE and TM plane waves (or plane wave spectra) incident on such multilayer structures. The use of the complex Poynting theorem in checking the computations, as well as monitoring powers and the stored electric or magnetic energy in any section of the multilayer stack, is illustrated, along with its use in designing alternating positive and negative index structures with optimal gain to compensate for losses in the negative index material. Finally, the robustness of PIM-NIM stacks with respect to randomness in the dimensions of the PIM-NIM structure is examined. This should be useful in determining the performance of such structures when they are physically fabricated.
    01/2014; 2:437-450. DOI:10.1109/ACCESS.2014.2321661