An international team of researchers studied the interaction of topology and non-Hermitian physics with nonlinear effects.In their papers published in the journal scienceThe group described the method of using polarized refracting crystals to construct optical waveguide lattices, and introduced experiments that introduced nonlinear effects. Piotr Roztocki and Roberto Morandotti, with INRS-Énergie, Materaux et Télécommunications, published a Perspective article in the same journal outlining the benefits of studying nonlinear systems and what the team is doing for this new work.
As pointed out by Roztocki and Morandotti, nonlinearity has been intensively studied. For example, its use in artificial networks and other digital electronic applications has greatly expanded the scope of such applications. But they also pointed out that there is still a lack of research in some areas. They pointed out, for example, that neither non-Hermitian elements nor systems including topological elements have been studied in depth. In this new work, the researchers try to resolve these gaps by studying the interaction between topology and non-Hermitian physics when nonlinear effects are introduced.
The team’s work involves the use of biased photorefractive crystals to construct optical waveguide lattices (with Su-Schrieffer-Heeger configuration). Such platforms have been widely used in various studies because they allow such easy access to their functions, especially the reconfiguration of waveguides.
The experiment involves modifying the nonlinear response of the waveguide to allow focusing and non-focusing, and then changing the way light passes through the lattice. By doing so, they were able to prove the destruction and restoration of states in non-Hermitian topologies, especially through nonlinear control.
The researchers also studied the sensitivity of the system, and these parts are described as special points rather than parts close to the protected state. They found that the stability of the inherited topology protection state will disappear from the protection mode, depending on how close they are to the abnormal point.
Roztocki and Morandotti believe that this work opens the door to further study of nonlinear effects in overlapping disciplines, which may have led to the development of new devices.
Use instability to see stable topology
Xia Shiqi and so on. Non-linear adjustment of PT symmetry and non-Hermitian topology state, science (2021). DOI: 10.1126/science.abf6873
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