Negative Index of Refraction in Atomic Gas

How do we perceive a negative index of refraction? What is the perfect lens? Harvard professor of Physics, Susanne Yelin, decribes the methods used to obtain a negative index of refraction.

Usually, in a vacuum the light just goes straight. If it goes in glass or water, it changes direction a little bit. Why? Because the index of refraction of water and glass is not 1. Water has one of about 1.3, and glass is around 1.5. What this does is refracts the light, so it changes the direction of the light.

Another effect is the application of the so-called perfect lens. Usually a lens can magnify or picture things, but the resolution is only as good as the length of the wavelengths. So typically with visible light it would be a little bit less than a micrometer. The perfect lens does not suffer from that kind of limitation. So, in principle, you have an infinitely good resolution.

In this case we can explicitly manipulate all matter such that for basically any given frequency the matter is transparent, but still couples very strongly with the light field, and therefore for example we can manipulate the index of refraction. However, the challenge in this material is really getting this magnetic permeability far away from one, and then actually into the minus regions.