Negative Refraction Without Metamaterials?
|Date/Time:||Thursday, 03 Feb 2011 - Wednesday, 02 Feb 2011|
|Channel:||Condensed Matter Physics|
Iowa State University and Ames Lab
The refractive index, n, of a transparent material usually is found by measuring the angle of refraction and using Snell's law. To date n is always positive in such materials. For opaque materials, e.g., metals, one usually cannot make this measurement due to high absorption. All other methods of measuring the refractive index of a metal require taking a square root and the positive sign is universally chosen. The advent of metamaterials has shown that a negative refractive index, hence angle of refraction, is possible. It has been observed in metamaterials . In this talk I will describe measurements of refraction in the visible region by thin wedge-shaped Cu films that show that in the region dominated by quasi-free electrons (Drude region) the refraction is negative, while in the interband-transition region the refraction is positive. Possible mechanisms for this phenomenon will be discussed, but to date, there is no satisfying explanation.