What is graphene Ohmic loss? What is its role in the plasmonic resonance effect when light incident onto a structure consisted of a monolayer graphene and a periodic nanostructure? 

further description:

A monolayer graphene film covers on a periodic structure(the element looks like a bowl; or imagine a cubic and scoop a ball from inside, then cut it equally into two, that is what the element looks like), then transfer a monolayer graphene film onto it. This project can be utilized to enhance the light absorption of graphene effectively.

In the paper, it said,    'The red-shifted plasmonic resonances  and suppressed reflectance are attributed to the presence  of graphene and the graphene Ohmic loss'.

And I don't understand it.