Recently, the research team led by Prof. Xu Jingjun, Prof. Chen Zhigang and Prof. Zhang Xinzheng of Nankai University achieved significant progress on terahertz topological photonics in collaboration with the team led by Prof. Roberto Morandotti of National Research Council of Canada. Based on the SSH-type microstructure, they demonstrated for the first time nonlinear generation and topologically tuned confinement of THz waves in a wedge-shaped lattice formed by an engineered lithium niobate chip in an experiment, and achieved direct visualization of the THz localization in the momentum space for the first time. They also compared both topologically trivial and nontrivial regime and analyzed the robustness of the confined mode against chiral perturbation. The research findings are presented in a paper titled "Topologically Tuned Terahertz Confinement in a Nonlinear Photonic Chip" published by the online-only journal of Light: Science & Applications.

During their work, the researchers demonstrated topologically controlled THz confinement with a lattice formed by an engineered lithium niobate chip. In their experiment with theoretical derivation, they observed and analyzed topologically tuned confinement of THz waves along the chip with respect to the variation of the photonic structure geometry, and the robustness of the confined mode against chiral perturbation was confirmed through further analysis. This research provides a flexible and convenient way for topologically tuned confinement of THz waves on demand, and finds a new approach to develop integrated topological circuits in compact THz devices with multiple functions, including wireless communication, biosensing and nondestructive testing. It is believed that more studies of different types of topological phenomena of the THz spectrum will deliver more interesting and efficient designs for THz-wave integration and operation.

Figure: An illustration and optical micrograph of nonlinear generation and confinement of THz-waves in an SSH-type microstructure with the LN structure undergoing a transition

Link: https://www.nature.com/articles/s41377-022-00823-7

(Edited and translated by Nankai News Team)