Terahertz probes of magnetic field induced spin reorientation in YFeO3 single crystal

Xian Lin, Junjie Jiang, Zuanming Jin, Dongyang Wang, Zhen Tian, Jiaguang Han, Zhenxiang Cheng, Guohong Ma
2015 Applied Physics Letters  
The near and far field coupling behavior in plasmonic and metamaterial systems have been extensively studied over last few years. However, most of the coupling mechanisms reported in the past have been passive in nature which actually fail to control the coupling mechanism dynamically in the plasmonic metamaterial lattice array. Here, we demonstrate a dynamic mode coupling between resonators in a hybrid metal-semiconductor metamaterial comprised of metallic concentric rings that are physically
more » ... hat are physically connected with silicon bridges. The dielectric function of silicon can be instantaneously modified by photodoped carriers thus tailoring the coupling characteristics between the metallic resonators. Based on the experimental results, a theoretical model is developed, which shows that the optical responses depend on mode coupling that originates from the variation of the damping rate and coupling coefficient of the resonance modes. This particular scheme enables an indepth understanding of the fundamental coupling mechanism and, therefore, the dynamic coupling enables functionalities and applications for designing on-demand reconfigurable metamaterial and plasmonic devices. In recent years, the concept of artificially engineered materials, known as metamaterials, has provided access to an even broader range of novel functionalities, such as negative refractive index 1-3 , perfect focusing 4 , cloaking 5-7 , absorbers 8 , sensing 9,10 , analogues of electromagnetically induced transparency 11-17 , and phase discontinuities 18-21 . The unique properties offered by metamaterials depend not only on the electromagnetic response of the individual meta-atoms, for instance the shape, the size, the conducting properties of the meta-atoms, and the surrounding environment 22,23 , but also on the coupling mechanism between the meta-atoms that form the two or three dimensional lattice array. Since the size of the meta-atoms is much smaller than the wavelength of light, interactions of the near-field distribution of the neighboring meta-atoms become very critical. As a result, the resonance properties of metamaterials can be substantially manipulated compared to those of an individual meta-atom. Thus, the near field interactions between adjacent meta-atoms have received considerable attention. Aside from the interesting fundamental phenomena that arise in these coupled meta-atoms, an understanding of the coupling mechanisms is believed to provide essential insight into novel design and applications of metamaterials based functional devices. Much of the published work has explored interactions between different resonators, where the coupling were studied passively by varying the geometrical parameters [24] [25] [26] [27] . In this article, we present a novel class of infrared light-driven active terahertz metamaterials that enable an observation of a dynamic coupling behavior between different resonators. The proposed planar
doi:10.1063/1.4913998 fatcat:ws7h3bophbav5bvmam4jcl6kwi