Asymmetric Wave Propagation in Non-Hamiltonian Structures

Wesleyan University, Middletown CT

Investigators

Abstract

Nontechnical Abstract This award supports research and education to develop new concepts for the control and management of wave propagation, for example radio or light waves, in efficient and reconfigurable ways. Gain mechanisms boost signals and help to transfer information, whereas loss is generally considered to degrade performance and so is to be avoided. The goal of this project is to develop new materials and circuit designs that carefully balance gain and loss and are based on fundamental theoretical concepts from seemingly unrelated areas of physics that have not been expressed in this context to control wave propagation. The PIs will explore the interplay of gain and loss and the unusual and unexpected phenomena that emerges. In the process, the research will result in new electronic circuit and media design strategies for efficient manipulation of electronic, optical, or more generally electromagnetic signals. The research team, consisting of both theoretical and experimental faculty and students, will equally engage computational methods with experimental realities helping to guide the focus and language of the theory as it develops. The experimental component revolves around exploring theoretical concepts within the context of conceptually straightforward electronic analogs. In addition to generating sound theoretical results, a steady stream of engineering based, yet theoretically savvy physicists will be produced. Technical Abstract This project will develop the fundamental physics of elemental building blocks that are uniquely capable of inducing reconfigurable asymmetric wave transport as either stand-alone devices or as duplicated units of arrays. This will be achieved via the interplay of strategically introduced non-Hermitian elements that can include nonlinearities and time dependence. The proposed strategies are based on variations of space-time reflection, or PT symmetry. Originally developed within the realm of quantum mechanics, were its usefulness is dubious, the ideas have had groundbreaking applicability to classical wave mechanics, although experimentally accessible avenues remain a challenge. This research group will use an experimental approach within the realm of equivalent electronic analogs in a tight-knit theoretical-experimental collaboration to develop several new aspects, including : (i) non-Hermitian, time-dependent scattering, exhibiting directional-dependent invisibility or mode-selective gain in multimode arrays, (ii) high figure of merit directional scattering from non-Hermitian nonlinear systems where the transmittance intensity of the fundamental frequency is enhanced, rather than diminished; (iii) the use of perfect impedance-matched isolation and unidirectional absorption in linear systems induced by gyro-active structures; and (iv) rapid state manipulation where PT-symmetry allows for directionally dependent accelerated pseudo-Hamiltonian dynamics. The strategies developed will allow for efficient prediction of the behavior in more complicated applications such as active antenna arrays, electro-acoustic integration, or complex metamaterial arrays, as they inevitably migrate into the realm of active elements inherent in non-Hermitian systems. These ultimate applications will become significantly less challenging if the fundamental theory and consequent design approaches are well grounded within this more transparent electronic context. The research team, consisting of both theoretical and experimental faculty and students, will equally engage computational methods with experimental realities helping to guide the focus and language of the theory as it develops. In addition to generating sound theoretical results, a steady stream of engineering based, yet theoretically savvy physicists will be produced. Both undergraduate and graduate students will acquire flexible and transferable skills in analytics, numerical computation, and experimental methods, in addition to forming international collaborative prospects through the team's established network.