EFRI NewLAW:: Non-reciprocal Elastic Wave Propagation in dynamically modulated Photo-elastic media

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The propagation of waves is a ubiquitous physical phenomenon at the heart of technological devices used in information transmission, telecommunication or medical imaging. One-way propagation of waves is emerging as a novel phenomenon that can disrupt ways in which current technologies employ waves. Conventionally and intuitively, one expects waves to propagate equally well in the forward or backward directions, however, certain media can break this symmetry. One-way or unidirectional propagation, also called non-reciprocal propagation of waves, restricts the transmission to only one direction. This unconventional property may enable totally new functionalities and ultimately new technologies and devices. This award supports fundamental research to provide needed knowledge for the development of solid materials that can support non-reciprocal propagation of elastic waves. Similar to the advent of the electrical diode, in which non-reciprocal elements formed the basis for modern electronics and computing, this research will enable future devices, whose operation relies on processing information transported by elastic waves in solids. Examples of such devices are surface or bulk acoustic wave devices as well as opto-mechanical systems used in telecommunication. This research involves several disciplines including materials science, mechanics, photonics and physics. The multi-disciplinary approach will help broaden participation of underrepresented groups in research and positively impact engineering education.The project will investigate solid chalcogenide glasses and phase change materials as a platform to produce surface and bulk elastic waves with unidirectional propagation. Chalcogenide materials possess large, fast, and reversible photo-elastic effects whereby the material elastic properties such as stiffness change upon illumination by light. This project exploits the spatiotemporal modulation of solid media's elastic properties through dynamical illumination, which has recently emerged as a potential universal method of breaking symmetry to achieve non-reciprocal elastic wave propagation within solids. The team will develop the theoretical, numerical and experimental methods to create a new conceptual and practical framework for developing elastic waves with non-conventional propagation in dynamically modulated elastic structures such as fibers or membranes. This will include defining the mechanisms, designs, and control parameters to break the symmetry in the direction of propagation of elastic waves and achieve non-reciprocal wave propagation in solid media.