Analysis of Doubly-Stacked Rotated Gratings Using Asymptotic Corrugations Boundary Conditions

In this paper, we present a highly efficient analysis of double-layered stacked gratings that are rotated from each other by any arbitrary angle using the asymptotic corrugations boundary conditions (ACBC) along with classical vector potentials. By casting the resultant system of linear equations into a homogeneous matrix equation, the eigenvalue problem can then be solved, after which the surface-wave dispersion diagram may be generated. In addition to the solutions for modal resonances under sourceless conditions, reflection and transmission analyses of plane-wave incidences constituting source-driven problems are also presented for both normal and oblique incidences. The properties of copolarization and cross-polarization levels in those scenarios are also discussed. The results computed by the code written based on this proposed modal method are compared and validated with those simulated using a commercial full-wave solver. A prototype of the structure was also manufactured and measured.