Kruk Sergey S, Wong Zi Jing, Pshenay-Severin Ekaterina, O'Brien Kevin, Neshev Dragomir N, Kivshar Yuri S, Zhang Xiang
Nonlinear Physics Center and Center for Ultrahigh Bandwidth Devices for Optical Systems (CUDOS), Research School of Physics and Engineering, The Australian National University, Canberra, Australian Capital Territory 2601, Australia.
NSF Nanoscale Science and Engineering Center, University of California, Berkeley, California 94720, USA.
Nat Commun. 2016 Apr 13;7:11329. doi: 10.1038/ncomms11329.
Strongly anisotropic media where the principal components of electric permittivity or magnetic permeability tensors have opposite signs are termed as hyperbolic media. Such media support propagating electromagnetic waves with extremely large wave vectors exhibiting unique optical properties. However, in all artificial and natural optical materials studied to date, the hyperbolic dispersion originates solely from the electric response. This restricts material functionality to one polarization of light and inhibits free-space impedance matching. Such restrictions can be overcome in media having components of opposite signs for both electric and magnetic tensors. Here we present the experimental demonstration of the magnetic hyperbolic dispersion in three-dimensional metamaterials. We measure metamaterial isofrequency contours and reveal the topological phase transition between the elliptic and hyperbolic dispersion. In the hyperbolic regime, we demonstrate the strong enhancement of thermal emission, which becomes directional, coherent and polarized. Our findings show the possibilities for realizing efficient impedance-matched hyperbolic media for unpolarized light.
介电常数或磁导率张量的主分量具有相反符号的强各向异性介质被称为双曲介质。这种介质支持具有极大波矢的传播电磁波，展现出独特的光学性质。然而，在迄今为止研究的所有人工和天然光学材料中，双曲色散仅源于电响应。这将材料功能限制于光的一种偏振，并抑制了自由空间阻抗匹配。在电张量和磁张量都具有相反符号分量的介质中，可以克服这些限制。在此，我们展示了三维超材料中磁双曲色散的实验证明。我们测量了超材料的等频轮廓，并揭示了椭圆色散和双曲色散之间的拓扑相变。在双曲 regime 中，我们展示了热发射的强烈增强，其变得具有方向性、相干性和偏振性。我们的发现展示了实现用于非偏振光的高效阻抗匹配双曲介质的可能性。
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