Does a negative refractive index always result in negative refraction? - Effect of loss

The phenomenon of negative refraction has been demonstrated experimentally and by numerical simulation assuming Drude and Lorentz models for the permittivity and permeability. It has been assumed that a negative refractive index results in negative refraction and hence will lead to a variety of exciting applications for metamaterials. Loss cannot be avoided in real metamaterials and in this paper, we analyze the effect of loss on negative refraction using experimentally extracted data for the permittivity, permeability and refractive index of a combined wire-Split Ring Resonator sample and for a sample with alternately oriented split ring resonators. Both samples are very lossy in the plasmonic resonance region and both display a negative refractive index. We show that obliquely incident waves on such samples may not always lead to negative refraction due to the effect of losses in the material.