Electromagnetic wave scattering from chiral layers

John Chih Liu, University of Pennsylvania

Abstract

This dissertation is an investigation of electromagnetic scattering from planar, spherical, and cylindrical chiral layers. The goal is to analyze, contrast and compare the scattering behavior of homogeneous and inhomogeneous chiral layers in these three canonic geometries. We review electromagnetic chirality and present an overview of existing techniques for determining the scattering characteristics of homogeneous planar chiral layers. We then formulate a Riccati equation for the scattering when the planar chiral layers are inhomogeneous along the axis of propagation. These techniques are applied to examine the use of chiral layers as anti-reflection screens. Of particular importance is the physical insight gained from our numerical examples. Part of the analytical tractability of planar layers is due to the fact that they are symmetric and unbounded along the axes transverse to the direction of propagation. However, this infinite nature is often unrealistic. A bounded, more practical configuration is the spherical layered geometry. We define wave functions appropriate to the spherical geometry and chiral nature of the medium and use them to determine the scattering of homogeneous, spherical, chiral layered configurations using boundary value techniques. Following the planar case, we formulate a matrix Riccati equation for the scattering from spherical chiral structures with radial inhomogeneities in permittivity, permeability, and chirality. High and low frequency limits, as well as weak reflection and constant impedance cases for this equation are examined analytically. We apply these results to investigate angular scattering from chiral coated spheres through differential scattering cross-sections and Mueller matrices. By definition, cylindrical layers do not display symmetry about the axes transverse to the direction of propagation. This suggests that cylindrical chiral layers exhibit inherently different behavior to the planar and spherical cases. Following analogously, we define wave functions applicable to cylindrical geometry, and use them to investigate several homogeneous, chiral, cylindrical scattering configurations through boundary value techniques. We formulate a cylindrical equivalent to the matrix Riccati equation for inhomogeneous chiral cylinders. Examining the angular scattering from chiral coated cylinders with appropriate scattering cross-sections and Mueller matrices, we remark on the relative contributions of geometry and degree of chirality on depolarization.

Subject Area

Electrical engineering|Materials science

Recommended Citation

Liu, John Chih, "Electromagnetic wave scattering from chiral layers" (1996). Dissertations available from ProQuest. AAI9627960.
https://repository.upenn.edu/dissertations/AAI9627960

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