Figure 1: Schematic illustration of the GPC band-stop filter.
From: Tunable Band-Stop Filters for Graphene Plasmons Based on Periodically Modulated Graphene
A silica layer with periodic thickness is used to periodically modulate the chemical potential of graphene. The chemical potential ratio between two regions is 
and the period is D = 2w = 50 nm. Influence of the silicon grating on GPs is eliminated since both d1 and d2 are always larger than 100 nm.
