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.