1] Instituto de Química-Física Rocasolano, Consejo Superior de Investigaciones Científcas, 28006 Madrid, Spain [2] DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark [3] Center for Nanostructured Graphene (CNG), Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
Sci Rep. 2013;3:2526. doi: 10.1038/srep02526.
Plasmons in metals can oscillate on a sub-wavelength length scale and this large-k response constitutes an inherent prerequisite for fascinating effects such as perfect imaging and intriguing wave phenomena associated with the epsilon-near-zero (ENZ) regime. While there is no upper cut-off within the local-response approximation (LRA) of the plasma polarization, nonlocal dynamics suppress response beyond ω/v(F), where v(F) is the Fermi velocity of the electron gas. Nonlocal response has previously been found to pose limitations to field-enhancement phenomena. Accounting for nonlocal hydrodynamic response, we show that perfect imaging is surprisingly only marginally affected by nonlocal properties of a metal slab, even for a deep subwavelength case and an extremely thin film. Similarly, for the ENZ response we find no indications of nonlocal response jeopardizing the basic behaviors anticipated from the LRA. Finally, our study of waveguiding of gap plasmons even shows a positive nonlocal influence on the propagation length.
金属中的等离子体可以在亚波长长度尺度上振荡，这种大 k 响应构成了完美成像等迷人效应以及与近零介电常数（epsilon-near-zero，ENZ）区相关的有趣波现象的固有前提。虽然在等离子体极化的局域响应近似（local-response approximation，LRA）中没有上限，但非局域动力学会抑制超过 ω/v(F) 的响应，其中 v(F) 是电子气的费米速度。先前已经发现非局域响应会对场增强现象造成限制。考虑到非局域流体动力学响应，我们表明，即使对于深亚波长情况和极薄的情况，完美成像也仅受到金属片的非局域性质的轻微影响。同样，对于 ENZ 响应，我们没有发现非局域响应会危及 LRA 预期的基本行为的迹象。最后，我们对间隙等离子体波导的研究甚至表明，非局域对传播长度有积极影响。
