Liberal Iñigo, Li Yue, Engheta Nader
Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
Department of Electronic Engineering, Tsinghua University, Beijing 100084, People's Republic of China.
Philos Trans A Math Phys Eng Sci. 2017 Mar 28;375(2090). doi: 10.1098/rsta.2016.0059.
Strengthening the magnetic response of matter at optical frequencies is of fundamental interest, as it provides additional information in spectroscopy, as well as alternative mechanisms to manipulate light at the nanoscale. Here, we demonstrate theoretically that epsilon-near-zero (ENZ) media can enhance the magnetic field concentration capabilities of dielectric resonators. We demonstrate that the magnetic field enhancement factor is unbounded in theory, and it diverges as the size of the ENZ host increases. In practice, the maximal enhancement factor is limited by dissipation losses in the host, and it is found via numerical simulations that ENZ hosts with moderate losses can enhance the performance of a circular dielectric rod resonator by around one order of magnitude. The physical mechanism behind this process is the strongly inhomogeneous magnetic field distributions induced by ENZ media in neighbouring dielectrics. We show that this is an intrinsic property of ENZ media, and that the occurrence of resonant enhancement is independent of the shape of the host. These results might find applications in spectroscopy, in sensing, in light emission and, in general, in investigating light-matter interactions beyond electric dipole transitions.This article is part of the themed issue 'New horizons for nanophotonics'.
增强物质在光频下的磁响应具有重要的基础研究意义，因为它能在光谱学中提供额外信息，还能在纳米尺度上提供操纵光的替代机制。在此，我们从理论上证明，近零介电常数（ENZ）介质可以增强介质谐振器的磁场集中能力。我们证明，磁场增强因子在理论上是无界的，并且随着ENZ主体尺寸的增加而发散。在实际中，最大增强因子受到主体中的耗散损耗限制，通过数值模拟发现，具有适度损耗的ENZ主体可以将圆形介质棒谐振器的性能提高约一个数量级。这一过程背后的物理机制是ENZ介质在相邻电介质中引起的强烈非均匀磁场分布。我们表明，这是ENZ介质的固有特性，并且共振增强的出现与主体的形状无关。这些结果可能在光谱学、传感、发光以及一般地在研究超越电偶极跃迁的光与物质相互作用中找到应用。本文是主题为“纳米光子学的新视野”的特刊的一部分。
