Proof of negative refraction: Beyond reasonable doubt?

摘要

The past two decades have witnessed a flurry of designs of material with a negative index of refraction. These designs have been verified by experimentally observing the refraction direction through a prism-shaped form of the material, and by numerically computing the phase velocity within the material. The possibility is demonstrated herein that - for the particular manner in which these verifications are performed - it is possible to obtain negatively refracted waves and the appearance of negative phase velocity even using “standard” homogeneous materials with a positive index of refraction. These possibilities stem (a) from Floquet-Bloch modes that are excited because of the periodic shape of the prism hypotenuse, and (b) from particular locations at which the phase is sampled. As a result, additional empirical evidence is required to unambiguously prove material negativity.