How to get the same magnitude of effective garphene permittivity .

hi i am trying to plot the effective permittivity of photonic crystal made up of several layers of dielectric material and graphene.
in the original results and my obtained results magnitude does not matched. i used the same parameters as that used in original paper. kindly help to figure out where the mistake. is. i attached the pic

a "photonic crystal" sounds like it would be anisotropic. Maybe that is your issue, you are looking at in at the wrong angle.