Electromagnetic wave diffraction on a “strip grating – ferromagnetic half-space” composite structure: surface-wave resonances

Abstract

Subject and Purpose. A theoretic study is given to the diff raction of a monochromatic plane E -polarized electromagnetic wave on a composite structure like a periodic strip grating bordering a half-space fi lled with a lossy homogeneous gyrotropic ferromagnetic medium. The work seeks to develop a method of the diff raction problem solution and determine diff raction characteristics of the electromagnetic wave interaction with the composite structure in the frequency region where the eff ective permeability of the ferromagnetic medium takes negative values. Methods and Methodology. The method of the diff raction problem solution is based on the analytical regularization idea. The initial diff raction problem in terms of Maxwell’s equations is equivalently reduced to the Riemann problem in theory of analytical functions. The problem is explicitly solved to yield an infi nite system of linear algebraic equations for the Fourier coeffi cients of the diff raction fi eld expansion in plane (Floquet) modes, which is solved by truncation. Results. A solution method has been developed for the diff raction problem of plane waves on a periodic strip grating bordering a ferromagnetic half-space. A theoretic prediction has been made that the E -polarized plane wave refl ection coeffi cient of the ferromagnetic half-space bordered by a strip grating has resonances in the frequency region where the medium permeability takes negative values. It has been found that these resonances are mainly caused by the repeated refl ection of the surface wave of the ferromagnetic half-space from the grating strip edges. Conclusion. The developed solution method for the plane electromagnetic wave diff raction on a periodic strip grating lying on the medium interface can be generalized to the consideration of planar ferromagnetic layers instead of the ferromagnetic half-space. The theoretically predicted resonances of the refl ection coeffi cients can be essential to the synthesis of radar absorbing coatings.