Nonreciprocal Magnetic Coupling Using Nonlinear Meta‐Atoms. Issue 19 (23rd July 2020)

• Record Type: Journal Article
• Authors: Zhao, Xiaoguang; Wu, Ke; Chen, Chunxu; Bifano, Thomas G.; Anderson, Stephan W.; Zhang, Xin
• Is Part Of: Advanced science. Volume 7:Issue 19(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-07-23
• Subjects: coupled mode theory -- magnetic coupling -- meta‐atoms -- nonlinear -- nonreciprocity; Science -- Periodicals; 505
• DOI: 10.1002/advs.202001443
• Languages: English
• ISSNs: 2198-3844

Abstract

Abstract: Breaking Lorentz reciprocity is fundamental to an array of functional radiofrequency (RF) and optical devices, such as isolators and circulators. The application of external excitation, such as magnetic fields and spatial–temporal modulation, has been employed to achieve nonreciprocal responses. Alternatively, nonlinear effects may also be employed to break reciprocity in a completely passive fashion. Herein, a coupled system comprised of linear and nonlinear meta‐atoms that achieves nonreciprocity based on the coupling and frequency detuning of its constituent meta‐atoms is presented. An analytical model is developed based on the coupled mode theory (CMT) in order to design and optimize the nonreciprocal meta‐atoms in this coupled system. Experimental demonstration of an RF isolator is performed, and the contrast between forward and backward propagation approximates 20 dB. Importantly, the use of the CMT model developed herein enables a generalizable capacity to predict the limitations of nonlinearity‐based nonreciprocity, thereby facilitating the development of novel approaches to breaking Lorentz reciprocity. The CMT model and implementation scheme presented in this work may be deployed in a wide range of applications, including integrated photonic circuits, optical metamaterials, and metasurfaces, among others. Abstract : Breaking Lorentz reciprocity is the foundation of an array of functional electromagnetic devices, and often requires external excitation. Magnetically coupled linear and nonlinear meta‐atoms are experimentally employed to achieve giant and controllable nonreciprocity. The physics of such a passive and magnet‐free nonreciprocal isolator are explored by using coupled mode theory for generalization of the presented approach.