Non-Hermitian topological coupler for elastic waves

Abstract

Non-Hermitian topological systems, by combining the advantages of topological robustness and sensitivity induced by non-Hermiticity, have recently emerged and attracted much research interest. Here, we propose a device based on the topological coupler in elastic waves with non-Hermiticity, which contains two topological domain walls and four ports. In this device, topological robustness routes the transmission of waves, while non-Hermiticity controls the gain or loss of waves as they propagate. These mechanisms result in continuous and quantitative control of the energy distribution ratio of each port. A non-Hermitian Hamiltonian is introduced to reveal the coupling mechanism of the topological coupler, and a scattering matrix is proposed to predict the energy distribution ratio of each port. The proposed topological coupler, which provides a new paradigm for the non-Hermitian topological systems, can be employed as a sensitive beam splitter or a coupler switch. Moreover, the topological coupler has potential applications in information processing and logic operation in elastic circuits or networks, and the paradigm also applies to other classical systems.

Perspectives for extraordinary elastic-wave control in non-Hermitian meta-structures

“…The out-ofplane displacement field presented in Figure 7(d) illustrates the two edge modes localized at the two edges. On the other hand, a recent thesis evaluated a topological coupler with four ports with non-Hermiticity (Meng et al, 2022). Combining the gain and loss control by the non-Hermiticity, highly efficient elastic-wave guiding with topological robustness was realized.…”

1D Photonic Topological Insulators Composed of Split Ring Resonators: A Mini Review

“…Currently, non-Hermitian topological photonics is an interesting research topic in topological physics. [420][421][422][423][424][425][426][427][428][429][430][431][432][433] Research on non-Hermitian photons based on PT symmetry has led to new design methods for photonic topological insulators. [434,435] The eigenvalues of open optical non-Hermitian systems are complex.…”

Robust optical mode converter based on topological waveguide arrays

“…In recent years, on-chip integrated photonic devices have gradually attracted research interest due to their advantages, such as low loss, high integration, and high controllability. On-chip integrated photonic devices represented by on-chip optical waveguides, [1] couplers, [2][3][4] splitters, [5] resonators, [6] mode converter, [7][8][9][10] gratings, [11] lasers, [11,13] optical modulators, [14,15] and photo-detectors [16] have matured in terms of design principles and manufacturing processes over decades. However, current integrated photonic devices are constrained by design principles, intrinsic material properties, and fabrication errors.…”