A discussion elsewhere made me realize that, even though this area is taking off like mad and it has been known for quite a while, a number of people are still unfamiliar with it, especially the concept. So I thought I'd give what I think is the best "tutorial" on this area. It is a Physics Today article co-written by John Pendry, so I believe is one of the discoverer/inventor of the metamaterial that exhibit such property.
I'm a bit familiar with this area because one of our graduate student is working in it. He's trying to build a set of these metamaterial into a waveguide structure. We're hoping to have electron beam bunches going through these material and maybe generate a reverse Cerenkov radiation. If we can do that, it will be a major accomplishment, not just in terms of the physics, but also for electron beam diagnostic. This is because the Cerenkov radiation will not be in the forward direction as in ordinary medium, along with other forms of radiation that can add to the noise of the detected signal, but rather in the backward direction, which is less noisy.
However, the task in doing this is formidable. The structures on printed circuit boards, and have to be alligned very carefully. We also don't know how well it will do when it encounters our electron beam. Previous results have also shown that the beam will excite several different modes that might drown out what we want.
Oh well. We shall see....