In addition, Soukoulis and his University of Karlsruhe colleagues have also shown that both the velocity of the individual wavelengths, called phase velocity, and the velocity of the wave packets, called group velocity, are both negative, which Soukoulis said accounts for the ability of negatively refracted light to seemingly defy Einstein’s theory of relativity and move backwards faster than the speed of light.
Elaborating, Soukoulis said, “When we have a metamaterial with a negative index of refraction at 1.5 micrometers that can disperse, or separate a wave into spectral components with different wavelengths, we can tune our lasers to play a lot of games with light. We can have a wavepacket hit a slab of negative index material, appear on the right-hand side of the material and begin to flow backward before the original pulse enters the negative index medium.” Continuing, he explained that the pulse flowing backward also releases a forward pulse out the end of the medium, a situation that causes the pulse entering the front of the material appear to move out the back almost instantly.
He predicted, “Snell’s law on the refraction of light is going to be different; a number of other laws will be different"
See movies that show what they are doing.
Metamaterials and superlens