Probing Rotated Weyl Physics on Nonlinear Lithium Niobate-on-Insulator Chips

Abstract

Topological photonics, featured by stable topological edge states resistant to perturbations, has been utilized to design robust integrated devices. Here, we present a study exploring the intriguing topological rotated Weyl physics in a 3D parameter space based on quaternary waveguide arrays on lithium niobate-oninsulator (LNOI) chips. Unlike previous works that focus on the Fermi arc surface states of a single Weyl structure, we can experimentally construct arbitrary interfaces between two Weyl structures whose orientations can be freely rotated in the synthetic parameter space. This intriguing system was difficult to realize in usual 3D Weyl semimetals due to lattice mismatch. We found whether the interface can host gapless topological interface states or not is determined by the relative rotational directions of the two Weyl structures. In the experiment, we have probed the local characteristics of the TISs through linear optical transmission and nonlinear second harmonic generation. Our study introduces a novel path to explore topological photonics on LNOI chips and various applications in integrated nonlinear and quantum optics.

Weyl interface states in non-Hermitian synthetic dimension

“…This is the Jackiw-Rebbi-type edge mode 48 , which only occurs in the case of real mass inversion. Notably, the rotational sphere is projected to a loop encircling the WP in the δl-δn plane, and the real mass inversion corresponds to rotating in the opposite direction encircling the WP 41 . In contrast, for the case with ϕ = π/2 with opposite non-Hermitian dimension [see Fig.…”

“…Fortunately, with the help of synthetic dimensions, it is possible to explore Weyl physics with lowerdimensional structures [32][33][34][35][36][37][38][39][40][41][42][43][44][45] . Although the synthetic dimensions have been widely studied in frequency [33][34][35] , spatial/temporal mode 36,37 , orbital angular momentum 38 , and parameter space [39][40][41] , most works were focused on the Hermitian dimension that alters the Hermitian properties of a system, while the non-Hermitian topology was studied in one-dimensional synthetic frequency dimension 42,43 . It is highly desirable to connect the synthetic dimension with higher-dimensional non-Hermitian framework to inspect non-Hermitian Weyl interface states.…”

Tracking Valley Topology with Synthetic Weyl Paths

“…Novel applications would be enlightened by the deepened and global understanding to the subtle yet fundamental topological valley physics. Last but not the least, our study provides a concrete example that unveils intricate high-dimension band topology through easily controllable low-dimension physical systems [62][63][64][65][66][67][68][69][70][71][72][73]. In fact, similar methodology can also be employed to construct synthetic WPs with larger charges, e.g., by introducing a modulation degree of freedom to Kekulé lattices [74][75][76][77][78].…”

Photonic Dirac nodal-line semimetals realized by a hypercrystal

“…This uncontrollable displacement will affect the observation of ideal TPT in photonic fourfold Dirac semimetals. Photonic crystals (PCs) provide a powerful platform for manipulating the lightmatter interactions [62][63][64][65][66]. In 2021, Hu et al, uncover that double-bowl state in photonic Dirac nodal line semimetal in the one-dimensional (1D) PCs [19].…”