Laboratory of Applied Research on Electromagnetics, Zhejiang University, Hangzhou 310027, China.
Proc Natl Acad Sci U S A. 2012 Aug 14;109(33):13194-7. doi: 10.1073/pnas.1210923109. Epub 2012 Jul 30.
Electromagnetic materials lacking local time-reversal symmetry, such as gyrotropic materials, are of keen interest and importance both scientifically and technologically. Scientifically, topologically nontrivial phenomena, such as photonic chiral edge states, allow for reflection-free transport even in the presence of large disorder. Technologically, nonreciprocal photonic devices, such as optical isolators and circulators, play critical roles in optical communication and computing technologies because of their ability to eliminate cross-talk and feedback. Nevertheless, most known natural materials that lack local time-reversal symmetry require strong external fields and function only in a limited range of the electromagnetic spectrum. By taking advantage of metamaterials capable of translating the property of unidirectional active electronic circuits into effective dielectric response, we introduce a microwave gyrotropic metamaterial that does not require an external magnetic bias. Strong bulk Faraday-like effects, observed in both simulations and experiments, confirm nonreciprocity of the effective medium. This approach is scalable to many other wavelengths, and it also illustrates an opportunity to synthesize exotic electromagnetic materials.
缺乏局域时间反转对称的电磁材料，如旋磁材料，在科学和技术上都具有强烈的兴趣和重要性。从科学角度来看，拓扑非平庸现象，如光子手性边缘态，即使在存在大的无序的情况下，也允许无反射传输。从技术角度来看，非互易光子器件，如光隔离器和环行器，由于其消除串扰和反馈的能力，在光通信和计算技术中起着至关重要的作用。然而，大多数已知的缺乏局域时间反转对称的天然材料需要强外场，并且仅在电磁光谱的有限范围内起作用。通过利用能够将单向有源电子电路的性质转换为有效介电响应的超材料，我们引入了一种不需要外部磁场偏置的微波旋磁超材料。在模拟和实验中都观察到了强体类法拉第效应，证实了有效媒质的非互易性。这种方法可扩展到许多其他波长，并且还说明了合成奇异电磁材料的机会。
