Modeling and Analysis of Optical Reflection and Transmission of Double Nano-slit Metallic Gratings
Date Issued
2011
Date
2011
Author(s)
Lin, Sun-Jung
Abstract
Double nano-slit metallic gratings are one-dimensional periodic structures which have two nano-slits within each grating period. The characteristics of optical transmission and reflection as the light is incident onto the double nano-slit metallic gratings will be dominated by the properties of each nano-slit and the optical coupling between of the nano-slits. In this thesis, an analytical model of the optical transmission and reflection properties for the light incidence onto nano-slit metallic gratings was derived. The metal nano-slit region of double nano-slit metallic gratings are similar to the five-layer planar waveguides of staggered metal and dielectric materials, which has two surface plasmon modes. Thus, when the light is incident onto the double nano-slit metallic gratings, two surface plasmon modes may be excited in the metal nano-slit region. The modal characteristic equation of the metal-dielectric staggered five-layer planar waveguides was also derived and the solution to the modal characteristic equation yields the effective refractive indices of the two surface plasmon modes which can be used to describe the propagation characteristics of these two surface plasmon modes in the metal slit region. The Fabry-Pérot interference may occur as the two surface plasmon modes bounces back and forth independently along the metal nano-slits due to the abrupt reflective index change at the top and bottom interfaces. In case of resonance, dips in the reflectivity spectrum and peaks in the transmittance spectrum will appear. The orthogonality of the two surface plasmon modes as well as the boundary condition were then used to derived the analytical model of the optical transmission and reflection of the double nano-slit metallic gratings. The results obtained by using the analytical model are in good agreement with those by using rigorous coupled wave analysis (RCWA). Although the analytical model is not completely accurate, it allows us to obtain new physical insight into the behavior of the surface plasmon modes in the double nano-slit metallic gratings and to calculate the numerical solutions with a considerably reduced computation time.
Subjects
Nano-slits
Metallic gratings
Surface plasmons
Fabry-Perot resonators
Reflection
Transmission
Type
thesis
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