Bragg gratings with parasitic scattering suppression for surface plasmon polaritons

In the present work, we numerically study the performance (reflectance and scattering /absorption losses) of dielectric Bragg gratings for surface plasmon polaritons using a rigorous coupled-wave analysis technique. We demonstrate that the main reason behind the low efficiency of such Bragg reflectors is the parasitic out-of-plane scattering of SPP at the grating ridges. As efficient approaches for scattering suppression, we propose an increase in the grating period at a fixed aspect ratio and the utilization of a two-layer geometry of the grating ridge. We show that these two approaches enable increasing the efficiency of the SPP Bragg grating by 15-35%. The obtained results may find applications in the design of high-efficiency plasmonic elements.