Dr.  Bing  Li
Northwestern Polytechnical University,  China

Title: Non-Hermitian Metasurfaces for Extraordinary Elastic-wave Manipulations of Higher-order Diffractions

Abstract:

The past decades have witnessed the remarkable development and explosive implications of meta-structures in elastic-wave steering under the Hermitian systems that disregard material loss. However, the reality of practical applications is inevitably intertwined with loss, leading to the dissipation of elastic wave energy. Traditionally, such losses were viewed as detrimental, potentially compromising the performance of elastic wave devices. Yet, a paradigm shift has emerged from recent groundbreaking research, which has uncovered the potential of strategically engineered loss/gain within non-Hermitian systems to facilitate remarkable wave steering phenomena. Through the meticulous design of loss and gain media, complex wave-matter interactions can be realized, encompassing unidirectional wave propagation, band merging, and enhanced sensing capabilities. The advent of non-Hermitian metasurfaces has opened new frontiers for elastic wave control, offering a reduced structure footprint in low-dimensional designs. Despite their promise, metasurfaces face inherent limitations stemming from their gradient index characteristics, which can constrain their capabilities. Achieving highly efficient wave manipulation in advanced artificial materials, with a focus on ultra-compact dimensions and easy fabrication, remains an open challenge. This work proposes a design strategy that leverages non-Hermitian modulation to surmount these obstacles. Specifically, we propose several active and passive non-Hermitian metasurfaces that enable unprecedented elastic-wave manipulations, including skin-like effects, asymmetric wave propagation, and perfect absorption.

Biography: