Simulation of the diffraction characteristics of a one-dimensional dual-periodicity superlattice

The diffraction characteristics of a dual-periodicity superlattice-a diffraction grating whose unit cell contains two different regions, one homogeneous and the other periodically nonhomogeneous-were numerically simulated. After choosing the second region to have sinusoidally varying permittivity, the widely used rigorous coupled-wave approach was applied to compute the reflection and transmission efficiency spectrums. An extensive parametric study revealed that the dual-periodicity superlattice exhibits anomalies in the long-wavelength regime which can be considered to be resonance anomalies (RAs), which are distinct from the Rayleigh-Wood anomalies. Also, double-periodicity superlattices exhibit RAs at higher wavelengths than single-periodicity superlattices.