Design and Analysis of Fully-Electronic Magnet-Free Non-Reciprocal Metamaterial

Abstract

Reciprocity is a fundamental and very important characteristics of the vast majority of electronic devices, and requires that signals travel in both forward and reverse directions in the same manner. Similarly, electromagnetic non-reciprocity or one way wave propagation, implies that the field created by a source at an observation point is not the same when source and observation points are interchanged. Non-reciprocal devices such as isolators, circulators, phase shifters, polarizers, switches, tunable resonators, tunable filters, and gyrators enable new applications from radio frequencies to optical frequencies. However, non-reciprocity has been implemented in the past using ferrites in the presence of an external permanent magnetic bias in devices (isolators, circulators, and gyrators) which make the device bulky, expensive, and incompatible with semiconductor technology. Therefore, in recent years, scientists have investigated various approaches to implement artificial non-reciprocity. The aim of this research is to design and analyze fully electronic, magnet-free, non-reciprocal (gyrotropic) devices. When a material, in the presence of a static magnet, exhibits different refractive indices for left and right handed elliptically/circularly polarized waves, it is called a gyrotropic material. The implementation of non-reciprocity requires time reversal symmetry breaking and can be realized with odd vector quantities that are odd (antisymmetric) under time reversal. Examples include magnetic fields, current, momentum, and orbital angular momentum. Travelling-wave resonant ring particles loaded by unidirectional components exhibit gyromagnetic properties by mimicking similar electron spin precession of a ferrite material in presence of magnetic bias. This artificial design offers numerous advantages in comparison with conventional approaches, such as smaller size, lower weight, lower cost, and flexible compatibility with semiconductor devices. This has been shown that two major properties of a magnet free, non-reciprocal devices, Faraday and Kerr rotation can be controlled by varying electric biasing conditions. Finally, this thesis presents several concepts, optimization approaches, and measurement environments, which have been investigated and developed during this MS program. These concepts and approaches include metamaterial design, implementing non-reciprocity in multi-layer configurations, and design consideration of practical devices.