All successful designs for negative refractive index in the optical range have so far used the idea of creating a negative magnetic permeability by means of the excitation of asymmetric currents ...

"The source of the negative-index response is fundamentally different ... they must be able to accept and focus light coming from a broad range of angles, independent of polarization.

and the result is an important step towards the creation of double-negative negative-index metamaterials (DN-NIMs) that operate in the visible range. Naturally occurring materials have a positive ...

According to Fig. 4a, the NIM remains active within a spectral range between 722 and 738 nm, and the refractive index is negative in a broader range, between 720 and 760 nm. Far-field ...