Roughness effects on absorption and scattering of left‐handed materials

Abstract

AbstractBistatic scattering and absorptivities from both Gaussian and exponentially correlated rough surfaces of the left‐handed materials (LHMs) are studied numerically for 2‐D geometries in a numerical Maxwell model. The multilevel UV method is employed to accelerate the matrix equation solver. Accuracy is ensured by energy conservation check. Using a set of physical surface parameters of root‐mean‐square heights and correlation lengths, numerical results are illustrated for absorptivities, bistatic scattering, and bistatic transmission of the LHMs. The numerical results show that the presence of the second opposite transmission, from lower medium to upper one for exponentially correlated LHM surfaces, dramatically reduces the absorptivities and enhances the bistatic scattering remarkably. In particular, the exponentially correlated roughness has negative effect on absorption for transverse electric (TE) case. Then all absorptivities for TE case are below that of the planar interface and decrease continuously with the increasing roughness. Due to both the Brewster angle effect and the opposite transmission across exponentially correlated interface, the absorptivities for the transverse magnetic (TM) case of the LHMs increase at first and decrease subsequently down below that of the planar interface. Both polarimetric absorptive characteristics are in completely contrary to those of the right‐handed materials (RHMs), where the absorptivities for both the TE and TM cases are monotonic increasing with the increase of roughness because of its fine‐scale surface features and the increasing effective surface areas. For Gaussian correlated LHM surfaces, however, the second opposite transmission does not exist, thus does not show any evident differences from RHMs, except for the maximum transmission in different directions and beam broadening. In addition, comparisons are also made with the second‐order small perturbation method and Kirchhoff's approximation. In contrary to RHM, the second‐order small perturbation method is no longer valid for TE case for both absorptivity and scattering from exponentially correlated LHM surfaces even for very small perturbation cases. Similar to RHM surfaces, the Kirchhoff's approximation can be only valid to the LHM surfaces with Gaussian correlation function.