Kerr effect in structured superluminal media

Kerr effect accounts for the change in refractive index of a material with the light intensity and appears in all known optical materials. In this work we analyze Kerr effect in structured superluminal media (e.g some specific types of resonators). We show that Kerr effect in these structures can be cancelled or even reversed (in comparison with the Kerr effect of the material composing the structure) depending on the group index of the structure. We also discuss some possible realizations of structured superluminal media.