The picture displays the core of the metamaterial with high index of refraction proposed by the researchers at Stanford University. Both high electric permittivity and magnetic permeability are needed in order to achieve a high refractive index in a metamaterial. Metallic inclusions allowing electric charge migration give a high permittivity, but usually a small permeability because of electric currents. The shape of the metallic inclusion needs to, therefore, be optimized in order to allow electric charges to move in non-loopy paths alone.
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