What is it about?
Reciprocity is a fundamental principle that follows the time reversal symmetry of physics. However, many practical applications require breaking time reversal symmetry, hence, are called nonreciprocal. This article aims at discussing time reversal symmetry, developing fundamental building block to achieve nonreciprocity leading to robust analytical model to explain electromagnetic rotation upon propagation through a nonreciprocal medium. Detailed mathematical derivation is presented for Faraday and Kerr rotation in the presence of external bias which breaks time reversal symmetry and leads to achieve nonreciprocal system. We validate our proposed model for conventional conditions and we compute the Faraday and Kerr rotation from a reported article using our proposed mathematical model and observed excellent agreement.
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Why is it important?
Measuring nonreciprocal polarization rotation is very difficult and in this work we developed a mathematical modelling which is very simple to implement in the lab to measure polarization rotation accurately from S parameters.
Perspectives
In a series of publication we developed the mathematical modelling, artificial nonreciprocity, tunability feature in nonreciprocal medium. Our proposed methods were validated by state of the art electromagnetic simulation followed by measurement in the lab which agreed pretty well.
Swadesh Poddar
Qorvo Inc, US
Read the Original
This page is a summary of: Analytical modeling of electromagnetic rotation in nonreciprocal media, Journal of Applied Physics, November 2022, American Institute of Physics,
DOI: 10.1063/5.0106896.
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Resources
Design and Analysis of an Electronically Tunable Magnet-Free Non-Reciprocal Metamaterial
In this communication, we develop and experimentally test a fully tunable magnet-free, non-reciprocal, split-ring resonator-based metamaterial. Non-reciprocity in the material response is introduced by bridging the split-ring gap with a biased field-effect transistor (FET) transistor, which allows the non-reciprocity to be tuned with respect to gate–source and drain–source bias conditions. As a measure of non-reciprocity, we consider the Faraday rotation of a normally incident linearly polarized planewave, which is a function of the co-polarized and cross-polarized S -parameters associated with two horn antennas that transmit and receive the wave. Faraday rotation is calculated with respect to the operating frequency of the horn antennas and manually measured with respect to drain–source current at the resonant frequency. Interestingly, we find a linear relationship between Faraday rotation and drain–source current at the resonance.
Automatic Measurement Technique of Electromagnetic Rotation in a Nonreciprocal Medium
Faraday rotation is a nonreciprocal rotation of wave polarization as a wave propagates. Faraday rotation is a critical property in a wide range of applications, from wireless communication to quantum memory, from bio-magnetic field detection to sensor applications. Characterizing the nonreciprocal polarization rotation accurately is very important for these applications. This article aims at developing a simple, automated test bench procedure based on simplified mathematical modeling to measure polarization rotation of an electromagnetic (EM) wave upon propagation through a nonreciprocal medium. A comprehensive measurement approach is developed from the scattering matrix. The proposed measurement procedure is demonstrated using an electronically tunable nonreciprocal metamaterial, and the accuracy of the proposed method is verified by comparison to the well-accepted conventional measurement technique, as well as 3-D EM simulation.
Computational Approach of Designing Magnetfree Nonreciprocal Metamaterial
This article aims at discussing computational approach to design magnet-free nonreciprocal metamaterial. Detailed mathematical derivation on Floquet mode analysis is presented for Faraday and Kerr rotation. Non-reciprocity in the designed metasurface is achieved in the presence of biased transistor loaded in the gap of circular ring resonator. Based on the derived mathematical model, co- and cross-polarized components have been extracted, which helps find Faraday and Kerr rotation and compare/contrast the reciprocal and nonreciprocal systems.
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