Dear Issam,
Sure, it's possible for the refractive index to be negative. Physically it means that the phase velocity (corresponding to the phase dynamics) of a wave propagating in such material is directed backwards, while group velocity (corresponding to the energy flow) is directed forward. Such material typically have very high loss: http://en.wikipedia.org/wiki/Negative_index_metamaterials
The metamaterials field is very active nowadays. There is several potential applications for negative refractive index materials : cloaking device, sub-wavelength imaging etc... We have also done some work for space applications as well (see attached publications). Veselago is a reference in the field.
Article Polarization scrambling with metallic meander structures for...
Article Metamaterials for optical and photonic applications for spac...
Negative refractive index material was predicted by a Russian scientist in 1968. We know that refractive index is square root of product of dielectric constant and magnetic permeability. Normal materials have both the parameter positive. If both are negative then we have left handed material also known as metamaterial. Such materials are not naturally available. one has to fabricate them. J. Pendry has published sevral papers and review on this topic.
Dear Prof. Issam Ashqer
- For normal metals: The imaginary part of the refractive index n`` have to be negative for the field to attenuate inside the metal (Einside=0) n`` comes as a solution in a negative exponent for a decaying electromagnetic wave, some people call it "the coeffcient of extintion" of the EM wave inside the metal. This is only for normal metals where Einside = 0 [1]
- For semiconductors: it is possible to have an electric field inside the semic. bulk in thermal equilibrium. So the meaning of n´´ changes [2,3]
References:
[1] Eletrodynamics of continuous media by L. Landau & E. Lifshitz, ch VII, pp 203, Pergamon 1984.
[2] http://web.mit.edu/6.012/www/SP07-L4.pdf
[3]
Chapter Local Electric Fields in Dielectric and Semiconductors
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