materials with an index of refraction of zero

[Trexman89]

http://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/nanostructured-metamaterial-enables-invisibility-cloak?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+IeeeSpectrum+%28IEEE+Spectrum %29

"We can even have amplification of light instead of its absorption. Here, for the first time, we showed that metamaterials can have a negative refractive index and amplify light."

this statement just ends up confusing me.

[mgb_phys]

They still take extra power, rather like a laser takes in energy from a pumping source to create a population inversion - then 'amplify' a single photon.