Topological edge states in photonic decorated trimer lattices

In recent years, topological insulators have been exten-sively studied in one-dimensional periodic systems, such as Su-Schrieffer-Heeger and trimer lattices. The remark-able feature of these one-dimensional models is that they support topological edge states, which are protected by lattice symmetry. To further study the role of lattice sym-metry in one-dimensional topological insulators, here we design a modified version of the conventional trimer lat-tices, i.e., decorated trimer lattices. Using the femtosecond laser writing technique, we experimentally establish a series of one-dimensional photonic decorated trimer lattices with and without inversion symmetry, thereby directly observ-ing three kinds of topological edge state. Interestingly, we demonstrate that the additional vertical intracell coupling strength in our model can change the energy band spec-trum, thereby generating unconventional topological edge states with a longer localization length in another boundary. This work offers novel insight into topological insulators in one-dimensional photonic lattices. (c) 2023 Optica Publishing Group

Automated summary

In recent years, extensive studies have been conducted on topological insulators in one-dimensional periodic systems, particularly Su-Schrieffer-Heeger and trimer lattices. These models support topological edge states protected by lattice symmetry. To further investigate lattice symmetry in one-dimensional topological insulators, a modified version of the conventional trimer lattices called decorated trimer lattices was designed. Experimental demonstrations were conducted using the femtosecond laser writing technique, resulting in the observation of different types of topological edge states. Interestingly, the addition of vertical intracell coupling strength in the model transformed the energy band spectrum and generated unconventional topological edge states with longer localization lengths at a different boundary. This work provides novel insights into one-dimensional topological insulators in photonic lattices.