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Anomalous refraction, diffraction, and imaging in metamaterials

机译：超材料中的异常折射，衍射和成像

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In the past several years, optical metamaterials (MMs) have attracted a considerable deal of interest because it may be anticipated that their properties can be shaped to an unprecedented extent relieving optics from some of its natural limitations. An inevitable first step toward this goal is the evaluation of the optical properties of specifically designed MMs. To date, apart from identifying chiral properties of very specific configurations, this is primarily done in retrieving an effective refractive index-mostly-only for normal incidence. On this basis suggestions for a perfect lens, exploiting this negative refractive index have been put forward by taking advantage of geometrical optics arguments. We show that this approach is pointless for realistic MMs. Instead we prove that the dispersion relation of normal modes in these MMs provides all the required information. Most of the relevant optical parameters, such as refraction and diffraction coefficients, can be derived from this relation. Imaging properties follow straightforwardly from that data. This general approach holds for any optical material, in particular, for all MMs in question. As an example, we apply it to the fishnet structure: one of the most prominent and best studied design approaches to date. We show that both refraction and diffraction properties are strongly spatially and temporally dispersive and they can even change sign. In detail, we study the effect of these peculiarities on imaging and refraction of finite beams. In particular, we discuss both the effect of the specific dispersion relation and the losses on the imaging properties. All our physical predictions are backed by rigorous numerical calculations and the agreement is almost perfect. Ultimately the main conclusion to be drawn is that a negative index of refraction is by no means a sufficient criterion to achieve negative refraction and/or perfect imaging.
机译：在过去的几年中，光学超材料（MM）引起了人们的极大兴趣，因为可以预料，其性能可以达到空前的程度，从而消除了光学技术的某些自然局限性。朝着这个目标的必然的第一步是评估专门设计的MM的光学性能。迄今为止，除了确定非常具体的构型的手性性质外，这主要是在获取有效折射率的过程中完成的，而折射率仅主要针对法向入射。在此基础上，提出了一种理想的透镜的建议，即利用几何光学的观点来利用这一负折射率。我们表明，这种方法对现实的MM没有意义。相反，我们证明了这些MM中正常模式的色散关系提供了所有必需的信息。大多数相关的光学参数，例如折射系数和衍射系数，都可以从这种关系中得出。成像特性直接从该数据得出。这种通用方法适用于任何光学材料，尤其适用于所有相关的MM。例如，我们将其应用于鱼网结构：这是迄今为止最杰出和研究最深入的设计方法之一。我们表明，折射和衍射特性在空间和时间上都具有很强的色散性，甚至可以改变符号。详细地，我们研究这些特性对有限光束的成像和折射的影响。特别是，我们讨论了特定色散关系的影响和损耗对成像特性的影响。我们所有的物理预测均以严格的数值计算为后盾，这一协议几乎是完美的。最终得出的主要结论是，负折射率绝不是实现负折射率和/或完美成像的充分标准。

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