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 diffraction of a monochromatic plane E-polarized electromagnetic wave on a composite structure like a periodic strip grating bordering a half-space filled with a lossy homogeneous gyrotropic ferromagnetic medium. The work seeks to develop a method of the diffraction problem solution and determine diffraction characteristics of the electromagnetic wave interaction with the composite structure in the frequency region where the effective permeability of the ferromagnetic medium takes negative values. Methods and Methodology. The method of the diffraction problem solution is based on the analytical regularization idea. The initial diffraction 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 infinite system of linear algebraic equations for the Fourier coefficients of the diffraction field expansion in plane (Floquet) modes, which is solved by truncation. Results. A solution method has been developed for the diffraction 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 reflection coefficient 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 reflection of the surface wave of the ferromagnetic half-space from the grating strip edges. Conclusion. The developed solution method for the plane electromagnetic wave diffraction 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 reflection coefficients can be essential to the synthesis of radar absorbing coatings.

Keywords

• diffraction
• ferromagnetic medium
• periodic strip grating
• riemann problem
• surface wave