Nonlinear and Time-Modulated Metamaterials: Applications at Microwave Frequencies
Metamaterials (the Greek prefix meta, means beyond) are artificially structured materials that interact with the incoming waves in extraordinary ways, beyond the properties of natural materials, yielding unusual and exotic electromagnetics phenomena. By careful engineering of the material properties, invoking nonlinear elements and/or time-modulating some of the material parameters, linearity and/or time-invariance can be broken in metamaterials, enabling extraordinary wave phenomena that open opportunities for the microwave engineering community, including the creation of nonreciprocal devices, frequency conversion, and more. In this dissertation, we explore, investigate, design, and fabricate metamaterials that open new applications for nonlinearity-based and time-varying devices, particularly in the context of enabling potential applications not possible in classical linear time-invariant devices. Although the proposed concepts apply to different scientific communities, including optics, photonics, quantum, and microwave engineering, we mainly focus on implementing these applications in the microwave frequency range utilizing the mature platform of printed circuit boards (PCB) and lumped circuit components. In our work, by carefully engineering nonlinearities in the proposed circuits, we develop novel nonreciprocal passive and bias-free elements for chirp radar systems, passive nonlinear isolators, asymmetric pulse shaping devices for separate manipulation of the rising and falling time in a circuit, nonlinearity-based microwave oscillators with phase-tristability for classical and quantum computing circuits. In parallel, by considering time-varying circuits, we realize parity-time symmetric microwave devices without the need for gain elements, space-time metasurfaces that allow routing the incident signal into arbitrary angles and frequencies, time- 6 switched transmission lines that demonstrate temporal interfaces, time reflections, and efficient frequency conversion.
Nonlinear Circuits, Time-Modulation, Metamaterials, Nonreciprocity, Metasurfaces, Electromagnetics and Photonics
City University of New York - City College
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