There is a very limited number of ways for artificially changing the refractive index of a medium. But if one could be able to arbitrarily increase it, unprecedented possibilities would open the road to a novel generation of optical devices.
In a paper in Nature Photonics (January 2011), E.DelRe, E.Spinozzi, A.J.Agranat and C.Conti demonstrate through theory and experiments that supercooled ferroelectrics (a class of "complex" optical media) display a largely tunable refractive index when acting on their thermal history and resorting to their out-of-equilibrium state.
The so called "polar nano-regions" furnish such a possibility, and lead to the demonstration of a nonliner optical behavior which is intensity independent and may provide the complete suppression of evanescent waves, with a potential impact in whole field of microscopy.
This may constitute the first example of a novel class of non-ergodic metamaterials, where the wavelength of light is effectively cancelled and the propagation is "Scale-Free", that is, beams propagate without distortion at any beam size and intensity.
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