Topological light routing and displaying based on square lattice photonic crystals

• Published in: Optics communications Vol. 570; p. 130889
• Main Authors: Gao, Yong-Feng, Yang, Ming, Chen, Zhi-Chen, He, Yue, He, Yi-Han, Zhou, Shu-Yang, Sun, Ming-Yang
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2024
• Subjects: Coupled topological waveguide-cavity system; Photonic crystals; Topological corner state; Topological edge state; Wide band gap; Topological edge state; Topological corner state; Coupled topological waveguide-cavity system; Photonic crystals; Wide band gap
• ISSN: 0030-4018
• DOI: 10.1016/j.optcom.2024.130889

Recently, the topological edge state (TES) and topological corner state (TCS) of high-order photonic topological insulators have attracted much attention due to their unique characteristics of providing a novel approach of manipulating light in lower dimensions. However, the topological band gap of square photonic crystals (PCs) based on SSH model is narrow, which hinders the generation of strongly localized states in the topological band gap. In this paper, unit cell with odd digits is proposed for obtaining the wider topological band gap, and the topological phase transition of PCs is achieved by translating on the unit cell. In addition, a high-performance dual channel photonic router composed of a trivial and two nontrivial PCs is designed, which can select the wave of specific frequency range routing to corresponding outport. Moreover, a coupled topological waveguide-cavity system, including a TES waveguide, four TCS cavities, and 1-shaped and 2-shaped topological resonant cavities with closed contour, is constructed. The energy of excitation source can be evanescently coupled to 1-shaped or 2-shaped cavity. There is a one-to-one relationship between digital shape display and signal frequency, which can be used as signal storage, attention device, coder, etc. Our work provides a new path to design complex topological circuitry for information processing. The significance of this work is as follows.•We propose the square lattice photonic crystals (PCs) with an odd number of lattice sites within the unit cell, and achieve PCs with distinct topological properties through lattice translation.•The robust topological edge states is generated in the Z-shaped topological waveguide even with defects by combining PCs with distinct topological properties.•A high-performance dual channel photonic router composed of a trivial and two nontrivial PCs is designed, waves with specific frequency range being routed to corresponding out port.•The nearly degenerate topological corner states (TCSs) with high localization property is generated in the constructed box-shaped structure.•We separate the TCSs into two groups with different frequencies by optimizing the size of the dielectric columns in the corner regions of box-shaped structure.•The coupled topological waveguide-cavity system is proposed to realize digital shape display, which can be used as signal storage, attention device, code word, encoder, etc.