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[摘要]：The seminal discovery that an ideal negative-index lens may overcome Abbe's diffraction limit has raised enormous interest in the field of metamaterials and of subwavelength focusing. This finding is based on the anomalous wave propagation in ideally isotropic and homogeneous metamaterials with negative index of refraction and low loss, provided they are available. We have designed a metamaterial lens based on one of the simplest metamaterial geometries, a cubic array of spheres, with the aim of verifying its imaging properties in a practical configuration. After a rigorous homogenization, we have shown that, for suitable designs, the effective bulk parameters may indeed provide a quasi-isotropic negative-index response, ideal for imaging applications. We have then tested the imaging properties for finite-size lenses, analyzing challenges and potentials of going beyond the diffraction limit in a practical setup. We have also explored an alternative venue to exploit the negative-index property of the designed metamaterial in a concave lens, in order to resolve subwavelength features in the far-field. Our results indicate that, although subwavelength resolution and evanescent-wave amplification are possible in metamaterial arrays, practical imaging beyond the diffraction limit is challenging and a careful design should consider the granularity, degree of isotropy, and transverse size of the metamaterial lens. (C) 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.3578138] |
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